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Diffstat (limited to 'DBI.pm')
| -rw-r--r-- | DBI.pm | 8323 |
1 files changed, 8323 insertions, 0 deletions
@@ -0,0 +1,8323 @@ +# $Id: DBI.pm 15327 2012-06-06 16:37:26Z timbo $ +# vim: ts=8:sw=4:et +# +# Copyright (c) 1994-2012 Tim Bunce Ireland +# +# See COPYRIGHT section in pod text below for usage and distribution rights. +# + +package DBI; + +require 5.008_001; + +BEGIN { +$VERSION = "1.622"; # ==> ALSO update the version in the pod text below! +} + +=head1 NAME + +DBI - Database independent interface for Perl + +=head1 SYNOPSIS + + use DBI; + + @driver_names = DBI->available_drivers; + %drivers = DBI->installed_drivers; + @data_sources = DBI->data_sources($driver_name, \%attr); + + $dbh = DBI->connect($data_source, $username, $auth, \%attr); + + $rv = $dbh->do($statement); + $rv = $dbh->do($statement, \%attr); + $rv = $dbh->do($statement, \%attr, @bind_values); + + $ary_ref = $dbh->selectall_arrayref($statement); + $hash_ref = $dbh->selectall_hashref($statement, $key_field); + + $ary_ref = $dbh->selectcol_arrayref($statement); + $ary_ref = $dbh->selectcol_arrayref($statement, \%attr); + + @row_ary = $dbh->selectrow_array($statement); + $ary_ref = $dbh->selectrow_arrayref($statement); + $hash_ref = $dbh->selectrow_hashref($statement); + + $sth = $dbh->prepare($statement); + $sth = $dbh->prepare_cached($statement); + + $rc = $sth->bind_param($p_num, $bind_value); + $rc = $sth->bind_param($p_num, $bind_value, $bind_type); + $rc = $sth->bind_param($p_num, $bind_value, \%attr); + + $rv = $sth->execute; + $rv = $sth->execute(@bind_values); + $rv = $sth->execute_array(\%attr, ...); + + $rc = $sth->bind_col($col_num, \$col_variable); + $rc = $sth->bind_columns(@list_of_refs_to_vars_to_bind); + + @row_ary = $sth->fetchrow_array; + $ary_ref = $sth->fetchrow_arrayref; + $hash_ref = $sth->fetchrow_hashref; + + $ary_ref = $sth->fetchall_arrayref; + $ary_ref = $sth->fetchall_arrayref( $slice, $max_rows ); + + $hash_ref = $sth->fetchall_hashref( $key_field ); + + $rv = $sth->rows; + + $rc = $dbh->begin_work; + $rc = $dbh->commit; + $rc = $dbh->rollback; + + $quoted_string = $dbh->quote($string); + + $rc = $h->err; + $str = $h->errstr; + $rv = $h->state; + + $rc = $dbh->disconnect; + +I<The synopsis above only lists the major methods and parameters.> + + +=head2 GETTING HELP + +If you have questions about DBI, or DBD driver modules, you can get +help from the I<dbi-users@perl.org> mailing list. You don't have to subscribe +to the list in order to post, though I'd recommend it. You can get help on +subscribing and using the list by emailing I<dbi-users-help@perl.org>. + +I don't recommend the DBI cpanforum (at http://www.cpanforum.com/dist/DBI) +because relatively few people read it compared with dbi-users@perl.org. + +To help you make the best use of the dbi-users mailing list, +and any other lists or forums you may use, I recommend that you read +"Getting Answers" by Mike Ash: L<http://mikeash.com/getting_answers.html>. + +If you think you've found a bug then please also read +"How to Report Bugs Effectively" by Simon Tatham: +L<http://www.chiark.greenend.org.uk/~sgtatham/bugs.html>. + +The DBI home page at L<http://dbi.perl.org/> and the DBI FAQ +at L<http://faq.dbi-support.com/> may be worth a visit. +They include links to other resources, but are rather out-dated. + +Before asking any questions, reread this document, consult the +archives and read the DBI FAQ. The archives are listed +at the end of this document and on the DBI home page. + +You might also like to read the Advanced DBI Tutorial at +L<http://www.slideshare.net/Tim.Bunce/dbi-advanced-tutorial-2007> + +This document often uses terms like I<references>, I<objects>, +I<methods>. If you're not familiar with those terms then it would +be a good idea to read at least the following perl manuals first: +L<perlreftut>, L<perldsc>, L<perllol>, and L<perlboot>. + +Please note that Tim Bunce does not maintain the mailing lists or the +web page (generous volunteers do that). So please don't send mail +directly to him; he just doesn't have the time to answer questions +personally. The I<dbi-users> mailing list has lots of experienced +people who should be able to help you if you need it. If you do email +Tim he is very likely to just forward it to the mailing list. + +=head2 NOTES + +This is the DBI specification that corresponds to DBI version 1.622 +(see L<DBI::Changes> for details). + +The DBI is evolving at a steady pace, so it's good to check that +you have the latest copy. + +The significant user-visible changes in each release are documented +in the L<DBI::Changes> module so you can read them by executing +C<perldoc DBI::Changes>. + +Some DBI changes require changes in the drivers, but the drivers +can take some time to catch up. Newer versions of the DBI have +added features that may not yet be supported by the drivers you +use. Talk to the authors of your drivers if you need a new feature +that is not yet supported. + +Features added after DBI 1.21 (February 2002) are marked in the +text with the version number of the DBI release they first appeared in. + +Extensions to the DBI API often use the C<DBIx::*> namespace. +See L</Naming Conventions and Name Space>. DBI extension modules +can be found at L<http://search.cpan.org/search?mode=module&query=DBIx>. +And all modules related to the DBI can be found at +L<http://search.cpan.org/search?query=DBI&mode=all>. + +=cut + +# The POD text continues at the end of the file. + +use Carp(); +use DynaLoader (); +use Exporter (); + +BEGIN { +@ISA = qw(Exporter DynaLoader); + +# Make some utility functions available if asked for +@EXPORT = (); # we export nothing by default +@EXPORT_OK = qw(%DBI %DBI_methods hash); # also populated by export_ok_tags: +%EXPORT_TAGS = ( + sql_types => [ qw( + SQL_GUID + SQL_WLONGVARCHAR + SQL_WVARCHAR + SQL_WCHAR + SQL_BIGINT + SQL_BIT + SQL_TINYINT + SQL_LONGVARBINARY + SQL_VARBINARY + SQL_BINARY + SQL_LONGVARCHAR + SQL_UNKNOWN_TYPE + SQL_ALL_TYPES + SQL_CHAR + SQL_NUMERIC + SQL_DECIMAL + SQL_INTEGER + SQL_SMALLINT + SQL_FLOAT + SQL_REAL + SQL_DOUBLE + SQL_DATETIME + SQL_DATE + SQL_INTERVAL + SQL_TIME + SQL_TIMESTAMP + SQL_VARCHAR + SQL_BOOLEAN + SQL_UDT + SQL_UDT_LOCATOR + SQL_ROW + SQL_REF + SQL_BLOB + SQL_BLOB_LOCATOR + SQL_CLOB + SQL_CLOB_LOCATOR + SQL_ARRAY + SQL_ARRAY_LOCATOR + SQL_MULTISET + SQL_MULTISET_LOCATOR + SQL_TYPE_DATE + SQL_TYPE_TIME + SQL_TYPE_TIMESTAMP + SQL_TYPE_TIME_WITH_TIMEZONE + SQL_TYPE_TIMESTAMP_WITH_TIMEZONE + SQL_INTERVAL_YEAR + SQL_INTERVAL_MONTH + SQL_INTERVAL_DAY + SQL_INTERVAL_HOUR + SQL_INTERVAL_MINUTE + SQL_INTERVAL_SECOND + SQL_INTERVAL_YEAR_TO_MONTH + SQL_INTERVAL_DAY_TO_HOUR + SQL_INTERVAL_DAY_TO_MINUTE + SQL_INTERVAL_DAY_TO_SECOND + SQL_INTERVAL_HOUR_TO_MINUTE + SQL_INTERVAL_HOUR_TO_SECOND + SQL_INTERVAL_MINUTE_TO_SECOND + DBIstcf_DISCARD_STRING + DBIstcf_STRICT + ) ], + sql_cursor_types => [ qw( + SQL_CURSOR_FORWARD_ONLY + SQL_CURSOR_KEYSET_DRIVEN + SQL_CURSOR_DYNAMIC + SQL_CURSOR_STATIC + SQL_CURSOR_TYPE_DEFAULT + ) ], # for ODBC cursor types + utils => [ qw( + neat neat_list $neat_maxlen dump_results looks_like_number + data_string_diff data_string_desc data_diff sql_type_cast + ) ], + profile => [ qw( + dbi_profile dbi_profile_merge dbi_profile_merge_nodes dbi_time + ) ], # notionally "in" DBI::Profile and normally imported from there +); + +$DBI::dbi_debug = 0; # mixture of bit fields and int sub-fields +$DBI::neat_maxlen = 1000; +$DBI::stderr = 2_000_000_000; # a very round number below 2**31 + +# If you get an error here like "Can't find loadable object ..." +# then you haven't installed the DBI correctly. Read the README +# then install it again. +if ( $ENV{DBI_PUREPERL} ) { + eval { bootstrap DBI } if $ENV{DBI_PUREPERL} == 1; + require DBI::PurePerl if $@ or $ENV{DBI_PUREPERL} >= 2; + $DBI::PurePerl ||= 0; # just to silence "only used once" warnings +} +else { + bootstrap DBI; +} + +$EXPORT_TAGS{preparse_flags} = [ grep { /^DBIpp_\w\w_/ } keys %{__PACKAGE__."::"} ]; + +Exporter::export_ok_tags(keys %EXPORT_TAGS); + +} + +# Alias some handle methods to also be DBI class methods +for (qw(trace_msg set_err parse_trace_flag parse_trace_flags)) { + no strict; + *$_ = \&{"DBD::_::common::$_"}; +} + +use strict; + +DBI->trace(split /=/, $ENV{DBI_TRACE}, 2) if $ENV{DBI_TRACE}; + +$DBI::connect_via ||= "connect"; + +# check if user wants a persistent database connection ( Apache + mod_perl ) +if ($INC{'Apache/DBI.pm'} && $ENV{MOD_PERL}) { + $DBI::connect_via = "Apache::DBI::connect"; + DBI->trace_msg("DBI connect via $DBI::connect_via in $INC{'Apache/DBI.pm'}\n"); +} + +# check for weaken support, used by ChildHandles +my $HAS_WEAKEN = eval { + require Scalar::Util; + # this will croak() if this Scalar::Util doesn't have a working weaken(). + Scalar::Util::weaken( \my $test ); # same test as in t/72childhandles.t + 1; +}; + +%DBI::installed_drh = (); # maps driver names to installed driver handles +sub installed_drivers { %DBI::installed_drh } +%DBI::installed_methods = (); # XXX undocumented, may change +sub installed_methods { %DBI::installed_methods } + +# Setup special DBI dynamic variables. See DBI::var::FETCH for details. +# These are dynamically associated with the last handle used. +tie $DBI::err, 'DBI::var', '*err'; # special case: referenced via IHA list +tie $DBI::state, 'DBI::var', '"state'; # special case: referenced via IHA list +tie $DBI::lasth, 'DBI::var', '!lasth'; # special case: return boolean +tie $DBI::errstr, 'DBI::var', '&errstr'; # call &errstr in last used pkg +tie $DBI::rows, 'DBI::var', '&rows'; # call &rows in last used pkg +sub DBI::var::TIESCALAR{ my $var = $_[1]; bless \$var, 'DBI::var'; } +sub DBI::var::STORE { Carp::croak("Can't modify \$DBI::${$_[0]} special variable") } + +# --- Driver Specific Prefix Registry --- + +my $dbd_prefix_registry = { + ad_ => { class => 'DBD::AnyData', }, + ado_ => { class => 'DBD::ADO', }, + amzn_ => { class => 'DBD::Amazon', }, + best_ => { class => 'DBD::BestWins', }, + csv_ => { class => 'DBD::CSV', }, + db2_ => { class => 'DBD::DB2', }, + dbi_ => { class => 'DBI', }, + dbm_ => { class => 'DBD::DBM', }, + df_ => { class => 'DBD::DF', }, + f_ => { class => 'DBD::File', }, + file_ => { class => 'DBD::TextFile', }, + go_ => { class => 'DBD::Gofer', }, + ib_ => { class => 'DBD::InterBase', }, + ing_ => { class => 'DBD::Ingres', }, + ix_ => { class => 'DBD::Informix', }, + jdbc_ => { class => 'DBD::JDBC', }, + mo_ => { class => 'DBD::MO', }, + monetdb_ => { class => 'DBD::monetdb', }, + msql_ => { class => 'DBD::mSQL', }, + mvsftp_ => { class => 'DBD::MVS_FTPSQL', }, + mysql_ => { class => 'DBD::mysql', }, + mx_ => { class => 'DBD::Multiplex', }, + nullp_ => { class => 'DBD::NullP', }, + odbc_ => { class => 'DBD::ODBC', }, + ora_ => { class => 'DBD::Oracle', }, + pg_ => { class => 'DBD::Pg', }, + pgpp_ => { class => 'DBD::PgPP', }, + plb_ => { class => 'DBD::Plibdata', }, + po_ => { class => 'DBD::PO', }, + proxy_ => { class => 'DBD::Proxy', }, + ram_ => { class => 'DBD::RAM', }, + rdb_ => { class => 'DBD::RDB', }, + sapdb_ => { class => 'DBD::SAP_DB', }, + snmp_ => { class => 'DBD::SNMP', }, + solid_ => { class => 'DBD::Solid', }, + spatialite_ => { class => 'DBD::Spatialite', }, + sponge_ => { class => 'DBD::Sponge', }, + sql_ => { class => 'DBI::DBD::SqlEngine', }, + sqlite_ => { class => 'DBD::SQLite', }, + syb_ => { class => 'DBD::Sybase', }, + sys_ => { class => 'DBD::Sys', }, + tdat_ => { class => 'DBD::Teradata', }, + tmpl_ => { class => 'DBD::Template', }, + tmplss_ => { class => 'DBD::TemplateSS', }, + tree_ => { class => 'DBD::TreeData', }, + tuber_ => { class => 'DBD::Tuber', }, + uni_ => { class => 'DBD::Unify', }, + vt_ => { class => 'DBD::Vt', }, + wmi_ => { class => 'DBD::WMI', }, + x_ => { }, # for private use + xbase_ => { class => 'DBD::XBase', }, + xl_ => { class => 'DBD::Excel', }, + yaswi_ => { class => 'DBD::Yaswi', }, +}; + +my %dbd_class_registry = map { $dbd_prefix_registry->{$_}->{class} => { prefix => $_ } } + grep { exists $dbd_prefix_registry->{$_}->{class} } + keys %{$dbd_prefix_registry}; + +sub dump_dbd_registry { + require Data::Dumper; + local $Data::Dumper::Sortkeys=1; + local $Data::Dumper::Indent=1; + print Data::Dumper->Dump([$dbd_prefix_registry], [qw($dbd_prefix_registry)]); +} + +# --- Dynamically create the DBI Standard Interface + +my $keeperr = { O=>0x0004 }; + +%DBI::DBI_methods = ( # Define the DBI interface methods per class: + + common => { # Interface methods common to all DBI handle classes + 'DESTROY' => { O=>0x004|0x10000 }, + 'CLEAR' => $keeperr, + 'EXISTS' => $keeperr, + 'FETCH' => { O=>0x0404 }, + 'FETCH_many' => { O=>0x0404 }, + 'FIRSTKEY' => $keeperr, + 'NEXTKEY' => $keeperr, + 'STORE' => { O=>0x0418 | 0x4 }, + _not_impl => undef, + can => { O=>0x0100 }, # special case, see dispatch + debug => { U =>[1,2,'[$debug_level]'], O=>0x0004 }, # old name for trace + dump_handle => { U =>[1,3,'[$message [, $level]]'], O=>0x0004 }, + err => $keeperr, + errstr => $keeperr, + state => $keeperr, + func => { O=>0x0006 }, + parse_trace_flag => { U =>[2,2,'$name'], O=>0x0404, T=>8 }, + parse_trace_flags => { U =>[2,2,'$flags'], O=>0x0404, T=>8 }, + private_data => { U =>[1,1], O=>0x0004 }, + set_err => { U =>[3,6,'$err, $errmsg [, $state, $method, $rv]'], O=>0x0010 }, + trace => { U =>[1,3,'[$trace_level, [$filename]]'], O=>0x0004 }, + trace_msg => { U =>[2,3,'$message_text [, $min_level ]' ], O=>0x0004, T=>8 }, + swap_inner_handle => { U =>[2,3,'$h [, $allow_reparent ]'] }, + private_attribute_info => { }, + visit_child_handles => { U => [2,3,'$coderef [, $info ]'], O=>0x0404, T=>4 }, + }, + dr => { # Database Driver Interface + 'connect' => { U =>[1,5,'[$db [,$user [,$passwd [,\%attr]]]]'], H=>3, O=>0x8000, T=>0x200 }, + 'connect_cached'=>{U=>[1,5,'[$db [,$user [,$passwd [,\%attr]]]]'], H=>3, O=>0x8000, T=>0x200 }, + 'disconnect_all'=>{ U =>[1,1], O=>0x0800, T=>0x200 }, + data_sources => { U =>[1,2,'[\%attr]' ], O=>0x0800, T=>0x200 }, + default_user => { U =>[3,4,'$user, $pass [, \%attr]' ], T=>0x200 }, + dbixs_revision => $keeperr, + }, + db => { # Database Session Class Interface + data_sources => { U =>[1,2,'[\%attr]' ], O=>0x0200 }, + take_imp_data => { U =>[1,1], O=>0x10000 }, + clone => { U =>[1,2,'[\%attr]'], T=>0x200 }, + connected => { U =>[1,0], O => 0x0004, T=>0x200, H=>3 }, + begin_work => { U =>[1,2,'[ \%attr ]'], O=>0x0400, T=>0x1000 }, + commit => { U =>[1,1], O=>0x0480|0x0800, T=>0x1000 }, + rollback => { U =>[1,1], O=>0x0480|0x0800, T=>0x1000 }, + 'do' => { U =>[2,0,'$statement [, \%attr [, @bind_params ] ]'], O=>0x3200 }, + last_insert_id => { U =>[5,6,'$catalog, $schema, $table_name, $field_name [, \%attr ]'], O=>0x2800 }, + preparse => { }, # XXX + prepare => { U =>[2,3,'$statement [, \%attr]'], O=>0xA200 }, + prepare_cached => { U =>[2,4,'$statement [, \%attr [, $if_active ] ]'], O=>0xA200 }, + selectrow_array => { U =>[2,0,'$statement [, \%attr [, @bind_params ] ]'], O=>0x2000 }, + selectrow_arrayref=>{U =>[2,0,'$statement [, \%attr [, @bind_params ] ]'], O=>0x2000 }, + selectrow_hashref=>{ U =>[2,0,'$statement [, \%attr [, @bind_params ] ]'], O=>0x2000 }, + selectall_arrayref=>{U =>[2,0,'$statement [, \%attr [, @bind_params ] ]'], O=>0x2000 }, + selectall_hashref=>{ U =>[3,0,'$statement, $keyfield [, \%attr [, @bind_params ] ]'], O=>0x2000 }, + selectcol_arrayref=>{U =>[2,0,'$statement [, \%attr [, @bind_params ] ]'], O=>0x2000 }, + ping => { U =>[1,1], O=>0x0404 }, + disconnect => { U =>[1,1], O=>0x0400|0x0800|0x10000, T=>0x200 }, + quote => { U =>[2,3, '$string [, $data_type ]' ], O=>0x0430 }, + quote_identifier=> { U =>[2,6, '$name [, ...] [, \%attr ]' ], O=>0x0430 }, + rows => $keeperr, + + tables => { U =>[1,6,'$catalog, $schema, $table, $type [, \%attr ]' ], O=>0x2200 }, + table_info => { U =>[1,6,'$catalog, $schema, $table, $type [, \%attr ]' ], O=>0x2200|0x8800 }, + column_info => { U =>[5,6,'$catalog, $schema, $table, $column [, \%attr ]'],O=>0x2200|0x8800 }, + primary_key_info=> { U =>[4,5,'$catalog, $schema, $table [, \%attr ]' ], O=>0x2200|0x8800 }, + primary_key => { U =>[4,5,'$catalog, $schema, $table [, \%attr ]' ], O=>0x2200 }, + foreign_key_info=> { U =>[7,8,'$pk_catalog, $pk_schema, $pk_table, $fk_catalog, $fk_schema, $fk_table [, \%attr ]' ], O=>0x2200|0x8800 }, + statistics_info => { U =>[6,7,'$catalog, $schema, $table, $unique_only, $quick, [, \%attr ]' ], O=>0x2200|0x8800 }, + type_info_all => { U =>[1,1], O=>0x2200|0x0800 }, + type_info => { U =>[1,2,'$data_type'], O=>0x2200 }, + get_info => { U =>[2,2,'$info_type'], O=>0x2200|0x0800 }, + }, + st => { # Statement Class Interface + bind_col => { U =>[3,4,'$column, \\$var [, \%attr]'] }, + bind_columns => { U =>[2,0,'\\$var1 [, \\$var2, ...]'] }, + bind_param => { U =>[3,4,'$parameter, $var [, \%attr]'] }, + bind_param_inout=> { U =>[4,5,'$parameter, \\$var, $maxlen, [, \%attr]'] }, + execute => { U =>[1,0,'[@args]'], O=>0x1040 }, + + bind_param_array => { U =>[3,4,'$parameter, $var [, \%attr]'] }, + bind_param_inout_array => { U =>[4,5,'$parameter, \\@var, $maxlen, [, \%attr]'] }, + execute_array => { U =>[2,0,'\\%attribs [, @args]'], O=>0x1040|0x4000 }, + execute_for_fetch => { U =>[2,3,'$fetch_sub [, $tuple_status]'], O=>0x1040|0x4000 }, + + fetch => undef, # alias for fetchrow_arrayref + fetchrow_arrayref => undef, + fetchrow_hashref => undef, + fetchrow_array => undef, + fetchrow => undef, # old alias for fetchrow_array + + fetchall_arrayref => { U =>[1,3, '[ $slice [, $max_rows]]'] }, + fetchall_hashref => { U =>[2,2,'$key_field'] }, + + blob_read => { U =>[4,5,'$field, $offset, $len [, \\$buf [, $bufoffset]]'] }, + blob_copy_to_file => { U =>[3,3,'$field, $filename_or_handleref'] }, + dump_results => { U =>[1,5,'$maxfieldlen, $linesep, $fieldsep, $filehandle'] }, + more_results => { U =>[1,1] }, + finish => { U =>[1,1] }, + cancel => { U =>[1,1], O=>0x0800 }, + rows => $keeperr, + + _get_fbav => undef, + _set_fbav => { T=>6 }, + }, +); + +while ( my ($class, $meths) = each %DBI::DBI_methods ) { + my $ima_trace = 0+($ENV{DBI_IMA_TRACE}||0); + while ( my ($method, $info) = each %$meths ) { + my $fullmeth = "DBI::${class}::$method"; + if (($DBI::dbi_debug & 0xF) == 15) { # quick hack to list DBI methods + # and optionally filter by IMA flags + my $O = $info->{O}||0; + printf "0x%04x %-20s\n", $O, $fullmeth + unless $ima_trace && !($O & $ima_trace); + } + DBI->_install_method($fullmeth, 'DBI.pm', $info); + } +} + +{ + package DBI::common; + @DBI::dr::ISA = ('DBI::common'); + @DBI::db::ISA = ('DBI::common'); + @DBI::st::ISA = ('DBI::common'); +} + +# End of init code + + +END { + return unless defined &DBI::trace_msg; # return unless bootstrap'd ok + local ($!,$?); + DBI->trace_msg(sprintf(" -- DBI::END (\$\@: %s, \$!: %s)\n", $@||'', $!||''), 2); + # Let drivers know why we are calling disconnect_all: + $DBI::PERL_ENDING = $DBI::PERL_ENDING = 1; # avoid typo warning + DBI->disconnect_all() if %DBI::installed_drh; +} + + +sub CLONE { + _clone_dbis() unless $DBI::PurePerl; # clone the DBIS structure + DBI->trace_msg("CLONE DBI for new thread\n"); + while ( my ($driver, $drh) = each %DBI::installed_drh) { + no strict 'refs'; + next if defined &{"DBD::${driver}::CLONE"}; + warn("$driver has no driver CLONE() function so is unsafe threaded\n"); + } + %DBI::installed_drh = (); # clear loaded drivers so they have a chance to reinitialize +} + +sub parse_dsn { + my ($class, $dsn) = @_; + $dsn =~ s/^(dbi):(\w*?)(?:\((.*?)\))?://i or return; + my ($scheme, $driver, $attr, $attr_hash) = (lc($1), $2, $3); + $driver ||= $ENV{DBI_DRIVER} || ''; + $attr_hash = { split /\s*=>?\s*|\s*,\s*/, $attr, -1 } if $attr; + return ($scheme, $driver, $attr, $attr_hash, $dsn); +} + +sub visit_handles { + my ($class, $code, $outer_info) = @_; + $outer_info = {} if not defined $outer_info; + my %drh = DBI->installed_drivers; + for my $h (values %drh) { + my $child_info = $code->($h, $outer_info) + or next; + $h->visit_child_handles($code, $child_info); + } + return $outer_info; +} + + +# --- The DBI->connect Front Door methods + +sub connect_cached { + # For library code using connect_cached() with mod_perl + # we redirect those calls to Apache::DBI::connect() as well + my ($class, $dsn, $user, $pass, $attr) = @_; + my $dbi_connect_method = ($DBI::connect_via eq "Apache::DBI::connect") + ? 'Apache::DBI::connect' : 'connect_cached'; + $attr = { + $attr ? %$attr : (), # clone, don't modify callers data + dbi_connect_method => $dbi_connect_method, + }; + return $class->connect($dsn, $user, $pass, $attr); +} + +sub connect { + my $class = shift; + my ($dsn, $user, $pass, $attr, $old_driver) = my @orig_args = @_; + my $driver; + + if ($attr and !ref($attr)) { # switch $old_driver<->$attr if called in old style + Carp::carp("DBI->connect using 'old-style' syntax is deprecated and will be an error in future versions"); + ($old_driver, $attr) = ($attr, $old_driver); + } + + my $connect_meth = $attr->{dbi_connect_method}; + $connect_meth ||= $DBI::connect_via; # fallback to default + + $dsn ||= $ENV{DBI_DSN} || $ENV{DBI_DBNAME} || '' unless $old_driver; + + if ($DBI::dbi_debug) { + local $^W = 0; + pop @_ if $connect_meth ne 'connect'; + my @args = @_; $args[2] = '****'; # hide password + DBI->trace_msg(" -> $class->$connect_meth(".join(", ",@args).")\n"); + } + Carp::croak('Usage: $class->connect([$dsn [,$user [,$passwd [,\%attr]]]])') + if (ref $old_driver or ($attr and not ref $attr) or ref $pass); + + # extract dbi:driver prefix from $dsn into $1 + $dsn =~ s/^dbi:(\w*?)(?:\((.*?)\))?://i + or '' =~ /()/; # ensure $1 etc are empty if match fails + my $driver_attrib_spec = $2 || ''; + + # Set $driver. Old style driver, if specified, overrides new dsn style. + $driver = $old_driver || $1 || $ENV{DBI_DRIVER} + or Carp::croak("Can't connect to data source '$dsn' " + ."because I can't work out what driver to use " + ."(it doesn't seem to contain a 'dbi:driver:' prefix " + ."and the DBI_DRIVER env var is not set)"); + + my $proxy; + if ($ENV{DBI_AUTOPROXY} && $driver ne 'Proxy' && $driver ne 'Sponge' && $driver ne 'Switch') { + my $dbi_autoproxy = $ENV{DBI_AUTOPROXY}; + $proxy = 'Proxy'; + if ($dbi_autoproxy =~ s/^dbi:(\w*?)(?:\((.*?)\))?://i) { + $proxy = $1; + $driver_attrib_spec = join ",", + ($driver_attrib_spec) ? $driver_attrib_spec : (), + ($2 ) ? $2 : (); + } + $dsn = "$dbi_autoproxy;dsn=dbi:$driver:$dsn"; + $driver = $proxy; + DBI->trace_msg(" DBI_AUTOPROXY: dbi:$driver($driver_attrib_spec):$dsn\n"); + } + # avoid recursion if proxy calls DBI->connect itself + local $ENV{DBI_AUTOPROXY} if $ENV{DBI_AUTOPROXY}; + + my %attributes; # take a copy we can delete from + if ($old_driver) { + %attributes = %$attr if $attr; + } + else { # new-style connect so new default semantics + %attributes = ( + PrintError => 1, + AutoCommit => 1, + ref $attr ? %$attr : (), + # attributes in DSN take precedence over \%attr connect parameter + $driver_attrib_spec ? (split /\s*=>?\s*|\s*,\s*/, $driver_attrib_spec, -1) : (), + ); + } + $attr = \%attributes; # now set $attr to refer to our local copy + + my $drh = $DBI::installed_drh{$driver} || $class->install_driver($driver) + or die "panic: $class->install_driver($driver) failed"; + + # attributes in DSN take precedence over \%attr connect parameter + $user = $attr->{Username} if defined $attr->{Username}; + $pass = $attr->{Password} if defined $attr->{Password}; + delete $attr->{Password}; # always delete Password as closure stores it securely + if ( !(defined $user && defined $pass) ) { + ($user, $pass) = $drh->default_user($user, $pass, $attr); + } + $attr->{Username} = $user; # force the Username to be the actual one used + + my $connect_closure = sub { + my ($old_dbh, $override_attr) = @_; + + #use Data::Dumper; + #warn "connect_closure: ".Data::Dumper::Dumper([$attr,\%attributes, $override_attr]); + + my $dbh; + unless ($dbh = $drh->$connect_meth($dsn, $user, $pass, $attr)) { + $user = '' if !defined $user; + $dsn = '' if !defined $dsn; + # $drh->errstr isn't safe here because $dbh->DESTROY may not have + # been called yet and so the dbh errstr would not have been copied + # up to the drh errstr. Certainly true for connect_cached! + my $errstr = $DBI::errstr; + # Getting '(no error string)' here is a symptom of a ref loop + $errstr = '(no error string)' if !defined $errstr; + my $msg = "$class connect('$dsn','$user',...) failed: $errstr"; + DBI->trace_msg(" $msg\n"); + # XXX HandleWarn + unless ($attr->{HandleError} && $attr->{HandleError}->($msg, $drh, $dbh)) { + Carp::croak($msg) if $attr->{RaiseError}; + Carp::carp ($msg) if $attr->{PrintError}; + } + $! = 0; # for the daft people who do DBI->connect(...) || die "$!"; + return $dbh; # normally undef, but HandleError could change it + } + + # merge any attribute overrides but don't change $attr itself (for closure) + my $apply = { ($override_attr) ? (%$attr, %$override_attr ) : %$attr }; + + # handle basic RootClass subclassing: + my $rebless_class = $apply->{RootClass} || ($class ne 'DBI' ? $class : ''); + if ($rebless_class) { + no strict 'refs'; + if ($apply->{RootClass}) { # explicit attribute (ie not static methd call class) + delete $apply->{RootClass}; + DBI::_load_class($rebless_class, 0); + } + unless (@{"$rebless_class\::db::ISA"} && @{"$rebless_class\::st::ISA"}) { + Carp::carp("DBI subclasses '$rebless_class\::db' and ::st are not setup, RootClass ignored"); + $rebless_class = undef; + $class = 'DBI'; + } + else { + $dbh->{RootClass} = $rebless_class; # $dbh->STORE called via plain DBI::db + DBI::_set_isa([$rebless_class], 'DBI'); # sets up both '::db' and '::st' + DBI::_rebless($dbh, $rebless_class); # appends '::db' + } + } + + if (%$apply) { + + if ($apply->{DbTypeSubclass}) { + my $DbTypeSubclass = delete $apply->{DbTypeSubclass}; + DBI::_rebless_dbtype_subclass($dbh, $rebless_class||$class, $DbTypeSubclass); + } + my $a; + foreach $a (qw(Profile RaiseError PrintError AutoCommit)) { # do these first + next unless exists $apply->{$a}; + $dbh->{$a} = delete $apply->{$a}; + } + while ( my ($a, $v) = each %$apply) { + eval { $dbh->{$a} = $v }; # assign in void context to avoid re-FETCH + warn $@ if $@; + } + } + + # confirm to driver (ie if subclassed) that we've connected sucessfully + # and finished the attribute setup. pass in the original arguments + $dbh->connected(@orig_args); #if ref $dbh ne 'DBI::db' or $proxy; + + DBI->trace_msg(" <- connect= $dbh\n") if $DBI::dbi_debug & 0xF; + + return $dbh; + }; + + my $dbh = &$connect_closure(undef, undef); + + $dbh->{dbi_connect_closure} = $connect_closure if $dbh; + + return $dbh; +} + + +sub disconnect_all { + keys %DBI::installed_drh; # reset iterator + while ( my ($name, $drh) = each %DBI::installed_drh ) { + $drh->disconnect_all() if ref $drh; + } +} + + +sub disconnect { # a regular beginners bug + Carp::croak("DBI->disconnect is not a DBI method (read the DBI manual)"); +} + + +sub install_driver { # croaks on failure + my $class = shift; + my($driver, $attr) = @_; + my $drh; + + $driver ||= $ENV{DBI_DRIVER} || ''; + + # allow driver to be specified as a 'dbi:driver:' string + $driver = $1 if $driver =~ s/^DBI:(.*?)://i; + + Carp::croak("usage: $class->install_driver(\$driver [, \%attr])") + unless ($driver and @_<=3); + + # already installed + return $drh if $drh = $DBI::installed_drh{$driver}; + + $class->trace_msg(" -> $class->install_driver($driver" + .") for $^O perl=$] pid=$$ ruid=$< euid=$>\n") + if $DBI::dbi_debug & 0xF; + + # --- load the code + my $driver_class = "DBD::$driver"; + eval qq{package # hide from PAUSE + DBI::_firesafe; # just in case + require $driver_class; # load the driver + }; + if ($@) { + my $err = $@; + my $advice = ""; + if ($err =~ /Can't find loadable object/) { + $advice = "Perhaps DBD::$driver was statically linked into a new perl binary." + ."\nIn which case you need to use that new perl binary." + ."\nOr perhaps only the .pm file was installed but not the shared object file." + } + elsif ($err =~ /Can't locate.*?DBD\/$driver\.pm in \@INC/) { + my @drv = $class->available_drivers(1); + $advice = "Perhaps the DBD::$driver perl module hasn't been fully installed,\n" + ."or perhaps the capitalisation of '$driver' isn't right.\n" + ."Available drivers: ".join(", ", @drv)."."; + } + elsif ($err =~ /Can't load .*? for module DBD::/) { + $advice = "Perhaps a required shared library or dll isn't installed where expected"; + } + elsif ($err =~ /Can't locate .*? in \@INC/) { + $advice = "Perhaps a module that DBD::$driver requires hasn't been fully installed"; + } + Carp::croak("install_driver($driver) failed: $err$advice\n"); + } + if ($DBI::dbi_debug & 0xF) { + no strict 'refs'; + (my $driver_file = $driver_class) =~ s/::/\//g; + my $dbd_ver = ${"$driver_class\::VERSION"} || "undef"; + $class->trace_msg(" install_driver: $driver_class version $dbd_ver" + ." loaded from $INC{qq($driver_file.pm)}\n"); + } + + # --- do some behind-the-scenes checks and setups on the driver + $class->setup_driver($driver_class); + + # --- run the driver function + $drh = eval { $driver_class->driver($attr || {}) }; + unless ($drh && ref $drh && !$@) { + my $advice = ""; + $@ ||= "$driver_class->driver didn't return a handle"; + # catch people on case in-sensitive systems using the wrong case + $advice = "\nPerhaps the capitalisation of DBD '$driver' isn't right." + if $@ =~ /locate object method/; + Carp::croak("$driver_class initialisation failed: $@$advice"); + } + + $DBI::installed_drh{$driver} = $drh; + $class->trace_msg(" <- install_driver= $drh\n") if $DBI::dbi_debug & 0xF; + $drh; +} + +*driver = \&install_driver; # currently an alias, may change + + +sub setup_driver { + my ($class, $driver_class) = @_; + my $h_type; + foreach $h_type (qw(dr db st)){ + my $h_class = $driver_class."::$h_type"; + no strict 'refs'; + push @{"${h_class}::ISA"}, "DBD::_::$h_type" + unless UNIVERSAL::isa($h_class, "DBD::_::$h_type"); + # The _mem class stuff is (IIRC) a crufty hack for global destruction + # timing issues in early versions of perl5 and possibly no longer needed. + my $mem_class = "DBD::_mem::$h_type"; + push @{"${h_class}_mem::ISA"}, $mem_class + unless UNIVERSAL::isa("${h_class}_mem", $mem_class) + or $DBI::PurePerl; + } +} + + +sub _rebless { + my $dbh = shift; + my ($outer, $inner) = DBI::_handles($dbh); + my $class = shift(@_).'::db'; + bless $inner => $class; + bless $outer => $class; # outer last for return +} + + +sub _set_isa { + my ($classes, $topclass) = @_; + my $trace = DBI->trace_msg(" _set_isa([@$classes])\n"); + foreach my $suffix ('::db','::st') { + my $previous = $topclass || 'DBI'; # trees are rooted here + foreach my $class (@$classes) { + my $base_class = $previous.$suffix; + my $sub_class = $class.$suffix; + my $sub_class_isa = "${sub_class}::ISA"; + no strict 'refs'; + if (@$sub_class_isa) { + DBI->trace_msg(" $sub_class_isa skipped (already set to @$sub_class_isa)\n") + if $trace; + } + else { + @$sub_class_isa = ($base_class) unless @$sub_class_isa; + DBI->trace_msg(" $sub_class_isa = $base_class\n") + if $trace; + } + $previous = $class; + } + } +} + + +sub _rebless_dbtype_subclass { + my ($dbh, $rootclass, $DbTypeSubclass) = @_; + # determine the db type names for class hierarchy + my @hierarchy = DBI::_dbtype_names($dbh, $DbTypeSubclass); + # add the rootclass prefix to each ('DBI::' or 'MyDBI::' etc) + $_ = $rootclass.'::'.$_ foreach (@hierarchy); + # load the modules from the 'top down' + DBI::_load_class($_, 1) foreach (reverse @hierarchy); + # setup class hierarchy if needed, does both '::db' and '::st' + DBI::_set_isa(\@hierarchy, $rootclass); + # finally bless the handle into the subclass + DBI::_rebless($dbh, $hierarchy[0]); +} + + +sub _dbtype_names { # list dbtypes for hierarchy, ie Informix=>ADO=>ODBC + my ($dbh, $DbTypeSubclass) = @_; + + if ($DbTypeSubclass && $DbTypeSubclass ne '1' && ref $DbTypeSubclass ne 'CODE') { + # treat $DbTypeSubclass as a comma separated list of names + my @dbtypes = split /\s*,\s*/, $DbTypeSubclass; + $dbh->trace_msg(" DbTypeSubclass($DbTypeSubclass)=@dbtypes (explicit)\n"); + return @dbtypes; + } + + # XXX will call $dbh->get_info(17) (=SQL_DBMS_NAME) in future? + + my $driver = $dbh->{Driver}->{Name}; + if ( $driver eq 'Proxy' ) { + # XXX Looking into the internals of DBD::Proxy is questionable! + ($driver) = $dbh->{proxy_client}->{application} =~ /^DBI:(.+?):/i + or die "Can't determine driver name from proxy"; + } + + my @dbtypes = (ucfirst($driver)); + if ($driver eq 'ODBC' || $driver eq 'ADO') { + # XXX will move these out and make extensible later: + my $_dbtype_name_regexp = 'Oracle'; # eg 'Oracle|Foo|Bar' + my %_dbtype_name_map = ( + 'Microsoft SQL Server' => 'MSSQL', + 'SQL Server' => 'Sybase', + 'Adaptive Server Anywhere' => 'ASAny', + 'ADABAS D' => 'AdabasD', + ); + + my $name; + $name = $dbh->func(17, 'GetInfo') # SQL_DBMS_NAME + if $driver eq 'ODBC'; + $name = $dbh->{ado_conn}->Properties->Item('DBMS Name')->Value + if $driver eq 'ADO'; + die "Can't determine driver name! ($DBI::errstr)\n" + unless $name; + + my $dbtype; + if ($_dbtype_name_map{$name}) { + $dbtype = $_dbtype_name_map{$name}; + } + else { + if ($name =~ /($_dbtype_name_regexp)/) { + $dbtype = lc($1); + } + else { # generic mangling for other names: + $dbtype = lc($name); + } + $dbtype =~ s/\b(\w)/\U$1/g; + $dbtype =~ s/\W+/_/g; + } + # add ODBC 'behind' ADO + push @dbtypes, 'ODBC' if $driver eq 'ADO'; + # add discovered dbtype in front of ADO/ODBC + unshift @dbtypes, $dbtype; + } + @dbtypes = &$DbTypeSubclass($dbh, \@dbtypes) + if (ref $DbTypeSubclass eq 'CODE'); + $dbh->trace_msg(" DbTypeSubclass($DbTypeSubclass)=@dbtypes\n"); + return @dbtypes; +} + +sub _load_class { + my ($load_class, $missing_ok) = @_; + DBI->trace_msg(" _load_class($load_class, $missing_ok)\n", 2); + no strict 'refs'; + return 1 if @{"$load_class\::ISA"}; # already loaded/exists + (my $module = $load_class) =~ s!::!/!g; + DBI->trace_msg(" _load_class require $module\n", 2); + eval { require "$module.pm"; }; + return 1 unless $@; + return 0 if $missing_ok && $@ =~ /^Can't locate \Q$module.pm\E/; + die $@; +} + + +sub init_rootclass { # deprecated + return 1; +} + + +*internal = \&DBD::Switch::dr::driver; + +sub driver_prefix { + my ($class, $driver) = @_; + return $dbd_class_registry{$driver}->{prefix} if exists $dbd_class_registry{$driver}; + return; +} + +sub available_drivers { + my($quiet) = @_; + my(@drivers, $d, $f); + local(*DBI::DIR, $@); + my(%seen_dir, %seen_dbd); + my $haveFileSpec = eval { require File::Spec }; + foreach $d (@INC){ + chomp($d); # Perl 5 beta 3 bug in #!./perl -Ilib from Test::Harness + my $dbd_dir = + ($haveFileSpec ? File::Spec->catdir($d, 'DBD') : "$d/DBD"); + next unless -d $dbd_dir; + next if $seen_dir{$d}; + $seen_dir{$d} = 1; + # XXX we have a problem here with case insensitive file systems + # XXX since we can't tell what case must be used when loading. + opendir(DBI::DIR, $dbd_dir) || Carp::carp "opendir $dbd_dir: $!\n"; + foreach $f (readdir(DBI::DIR)){ + next unless $f =~ s/\.pm$//; + next if $f eq 'NullP'; + if ($seen_dbd{$f}){ + Carp::carp "DBD::$f in $d is hidden by DBD::$f in $seen_dbd{$f}\n" + unless $quiet; + } else { + push(@drivers, $f); + } + $seen_dbd{$f} = $d; + } + closedir(DBI::DIR); + } + + # "return sort @drivers" will not DWIM in scalar context. + return wantarray ? sort @drivers : @drivers; +} + +sub installed_versions { + my ($class, $quiet) = @_; + my %error; + my %version = ( DBI => $DBI::VERSION ); + $version{"DBI::PurePerl"} = $DBI::PurePerl::VERSION + if $DBI::PurePerl; + for my $driver ($class->available_drivers($quiet)) { + next if $DBI::PurePerl && grep { -d "$_/auto/DBD/$driver" } @INC; + my $drh = eval { + local $SIG{__WARN__} = sub {}; + $class->install_driver($driver); + }; + ($error{"DBD::$driver"}=$@),next if $@; + no strict 'refs'; + my $vers = ${"DBD::$driver" . '::VERSION'}; + $version{"DBD::$driver"} = $vers || '?'; + } + if (wantarray) { + return map { m/^DBD::(\w+)/ ? ($1) : () } sort keys %version; + } + if (!defined wantarray) { # void context + require Config; # add more detail + $version{OS} = "$^O\t($Config::Config{osvers})"; + $version{Perl} = "$]\t($Config::Config{archname})"; + $version{$_} = (($error{$_} =~ s/ \(\@INC.*//s),$error{$_}) + for keys %error; + printf " %-16s: %s\n",$_,$version{$_} + for reverse sort keys %version; + } + return \%version; +} + + +sub data_sources { + my ($class, $driver, @other) = @_; + my $drh = $class->install_driver($driver); + my @ds = $drh->data_sources(@other); + return @ds; +} + + +sub neat_list { + my ($listref, $maxlen, $sep) = @_; + $maxlen = 0 unless defined $maxlen; # 0 == use internal default + $sep = ", " unless defined $sep; + join($sep, map { neat($_,$maxlen) } @$listref); +} + + +sub dump_results { # also aliased as a method in DBD::_::st + my ($sth, $maxlen, $lsep, $fsep, $fh) = @_; + return 0 unless $sth; + $maxlen ||= 35; + $lsep ||= "\n"; + $fh ||= \*STDOUT; + my $rows = 0; + my $ref; + while($ref = $sth->fetch) { + print $fh $lsep if $rows++ and $lsep; + my $str = neat_list($ref,$maxlen,$fsep); + print $fh $str; # done on two lines to avoid 5.003 errors + } + print $fh "\n$rows rows".($DBI::err ? " ($DBI::err: $DBI::errstr)" : "")."\n"; + $rows; +} + + +sub data_diff { + my ($a, $b, $logical) = @_; + + my $diff = data_string_diff($a, $b); + return "" if $logical and !$diff; + + my $a_desc = data_string_desc($a); + my $b_desc = data_string_desc($b); + return "" if !$diff and $a_desc eq $b_desc; + + $diff ||= "Strings contain the same sequence of characters" + if length($a); + $diff .= "\n" if $diff; + return "a: $a_desc\nb: $b_desc\n$diff"; +} + + +sub data_string_diff { + # Compares 'logical' characters, not bytes, so a latin1 string and an + # an equivalent Unicode string will compare as equal even though their + # byte encodings are different. + my ($a, $b) = @_; + unless (defined $a and defined $b) { # one undef + return "" + if !defined $a and !defined $b; + return "String a is undef, string b has ".length($b)." characters" + if !defined $a; + return "String b is undef, string a has ".length($a)." characters" + if !defined $b; + } + + require utf8; + # hack to cater for perl 5.6 + *utf8::is_utf8 = sub { (DBI::neat(shift)=~/^"/) } unless defined &utf8::is_utf8; + + my @a_chars = (utf8::is_utf8($a)) ? unpack("U*", $a) : unpack("C*", $a); + my @b_chars = (utf8::is_utf8($b)) ? unpack("U*", $b) : unpack("C*", $b); + my $i = 0; + while (@a_chars && @b_chars) { + ++$i, shift(@a_chars), shift(@b_chars), next + if $a_chars[0] == $b_chars[0];# compare ordinal values + my @desc = map { + $_ > 255 ? # if wide character... + sprintf("\\x{%04X}", $_) : # \x{...} + chr($_) =~ /[[:cntrl:]]/ ? # else if control character ... + sprintf("\\x%02X", $_) : # \x.. + chr($_) # else as themselves + } ($a_chars[0], $b_chars[0]); + # highlight probable double-encoding? + foreach my $c ( @desc ) { + next unless $c =~ m/\\x\{08(..)}/; + $c .= "='" .chr(hex($1)) ."'" + } + return sprintf "Strings differ at index $i: a[$i]=$desc[0], b[$i]=$desc[1]"; + } + return "String a truncated after $i characters" if @b_chars; + return "String b truncated after $i characters" if @a_chars; + return ""; +} + + +sub data_string_desc { # describe a data string + my ($a) = @_; + require bytes; + require utf8; + + # hacks to cater for perl 5.6 + *utf8::is_utf8 = sub { (DBI::neat(shift)=~/^"/) } unless defined &utf8::is_utf8; + *utf8::valid = sub { 1 } unless defined &utf8::valid; + + # Give sufficient info to help diagnose at least these kinds of situations: + # - valid UTF8 byte sequence but UTF8 flag not set + # (might be ascii so also need to check for hibit to make it worthwhile) + # - UTF8 flag set but invalid UTF8 byte sequence + # could do better here, but this'll do for now + my $utf8 = sprintf "UTF8 %s%s", + utf8::is_utf8($a) ? "on" : "off", + utf8::valid($a||'') ? "" : " but INVALID encoding"; + return "$utf8, undef" unless defined $a; + my $is_ascii = $a =~ m/^[\000-\177]*$/; + return sprintf "%s, %s, %d characters %d bytes", + $utf8, $is_ascii ? "ASCII" : "non-ASCII", + length($a), bytes::length($a); +} + + +sub connect_test_perf { + my($class, $dsn,$dbuser,$dbpass, $attr) = @_; + Carp::croak("connect_test_perf needs hash ref as fourth arg") unless ref $attr; + # these are non standard attributes just for this special method + my $loops ||= $attr->{dbi_loops} || 5; + my $par ||= $attr->{dbi_par} || 1; # parallelism + my $verb ||= $attr->{dbi_verb} || 1; + my $meth ||= $attr->{dbi_meth} || 'connect'; + print "$dsn: testing $loops sets of $par connections:\n"; + require "FileHandle.pm"; # don't let toke.c create empty FileHandle package + local $| = 1; + my $drh = $class->install_driver($dsn) or Carp::croak("Can't install $dsn driver\n"); + # test the connection and warm up caches etc + $drh->connect($dsn,$dbuser,$dbpass) or Carp::croak("connect failed: $DBI::errstr"); + my $t1 = dbi_time(); + my $loop; + for $loop (1..$loops) { + my @cons; + print "Connecting... " if $verb; + for (1..$par) { + print "$_ "; + push @cons, ($drh->connect($dsn,$dbuser,$dbpass) + or Carp::croak("connect failed: $DBI::errstr\n")); + } + print "\nDisconnecting...\n" if $verb; + for (@cons) { + $_->disconnect or warn "disconnect failed: $DBI::errstr" + } + } + my $t2 = dbi_time(); + my $td = $t2 - $t1; + printf "$meth %d and disconnect them, %d times: %.4fs / %d = %.4fs\n", + $par, $loops, $td, $loops*$par, $td/($loops*$par); + return $td; +} + + +# Help people doing DBI->errstr, might even document it one day +# XXX probably best moved to cheaper XS code if this gets documented +sub err { $DBI::err } +sub errstr { $DBI::errstr } + + +# --- Private Internal Function for Creating New DBI Handles + +# XXX move to PurePerl? +*DBI::dr::TIEHASH = \&DBI::st::TIEHASH; +*DBI::db::TIEHASH = \&DBI::st::TIEHASH; + + +# These three special constructors are called by the drivers +# The way they are called is likely to change. + +our $shared_profile; + +sub _new_drh { # called by DBD::<drivername>::driver() + my ($class, $initial_attr, $imp_data) = @_; + # Provide default storage for State,Err and Errstr. + # Note that these are shared by all child handles by default! XXX + # State must be undef to get automatic faking in DBI::var::FETCH + my ($h_state_store, $h_err_store, $h_errstr_store) = (undef, 0, ''); + my $attr = { + # these attributes get copied down to child handles by default + 'State' => \$h_state_store, # Holder for DBI::state + 'Err' => \$h_err_store, # Holder for DBI::err + 'Errstr' => \$h_errstr_store, # Holder for DBI::errstr + 'TraceLevel' => 0, + FetchHashKeyName=> 'NAME', + %$initial_attr, + }; + my ($h, $i) = _new_handle('DBI::dr', '', $attr, $imp_data, $class); + + # XXX DBI_PROFILE unless DBI::PurePerl because for some reason + # it kills the t/zz_*_pp.t tests (they silently exit early) + if (($ENV{DBI_PROFILE} && !$DBI::PurePerl) || $shared_profile) { + # The profile object created here when the first driver is loaded + # is shared by all drivers so we end up with just one set of profile + # data and thus the 'total time in DBI' is really the true total. + if (!$shared_profile) { # first time + $h->{Profile} = $ENV{DBI_PROFILE}; # write string + $shared_profile = $h->{Profile}; # read and record object + } + else { + $h->{Profile} = $shared_profile; + } + } + return $h unless wantarray; + ($h, $i); +} + +sub _new_dbh { # called by DBD::<drivername>::dr::connect() + my ($drh, $attr, $imp_data) = @_; + my $imp_class = $drh->{ImplementorClass} + or Carp::croak("DBI _new_dbh: $drh has no ImplementorClass"); + substr($imp_class,-4,4) = '::db'; + my $app_class = ref $drh; + substr($app_class,-4,4) = '::db'; + $attr->{Err} ||= \my $err; + $attr->{Errstr} ||= \my $errstr; + $attr->{State} ||= \my $state; + _new_handle($app_class, $drh, $attr, $imp_data, $imp_class); +} + +sub _new_sth { # called by DBD::<drivername>::db::prepare) + my ($dbh, $attr, $imp_data) = @_; + my $imp_class = $dbh->{ImplementorClass} + or Carp::croak("DBI _new_sth: $dbh has no ImplementorClass"); + substr($imp_class,-4,4) = '::st'; + my $app_class = ref $dbh; + substr($app_class,-4,4) = '::st'; + _new_handle($app_class, $dbh, $attr, $imp_data, $imp_class); +} + + +# end of DBI package + + + +# -------------------------------------------------------------------- +# === The internal DBI Switch pseudo 'driver' class === + +{ package # hide from PAUSE + DBD::Switch::dr; + DBI->setup_driver('DBD::Switch'); # sets up @ISA + + $DBD::Switch::dr::imp_data_size = 0; + $DBD::Switch::dr::imp_data_size = 0; # avoid typo warning + my $drh; + + sub driver { + return $drh if $drh; # a package global + + my $inner; + ($drh, $inner) = DBI::_new_drh('DBD::Switch::dr', { + 'Name' => 'Switch', + 'Version' => $DBI::VERSION, + 'Attribution' => "DBI $DBI::VERSION by Tim Bunce", + }); + Carp::croak("DBD::Switch init failed!") unless ($drh && $inner); + return $drh; + } + sub CLONE { + undef $drh; + } + + sub FETCH { + my($drh, $key) = @_; + return DBI->trace if $key eq 'DebugDispatch'; + return undef if $key eq 'DebugLog'; # not worth fetching, sorry + return $drh->DBD::_::dr::FETCH($key); + undef; + } + sub STORE { + my($drh, $key, $value) = @_; + if ($key eq 'DebugDispatch') { + DBI->trace($value); + } elsif ($key eq 'DebugLog') { + DBI->trace(-1, $value); + } else { + $drh->DBD::_::dr::STORE($key, $value); + } + } +} + + +# -------------------------------------------------------------------- +# === OPTIONAL MINIMAL BASE CLASSES FOR DBI SUBCLASSES === + +# We only define default methods for harmless functions. +# We don't, for example, define a DBD::_::st::prepare() + +{ package # hide from PAUSE + DBD::_::common; # ====== Common base class methods ====== + use strict; + + # methods common to all handle types: + + sub _not_impl { + my ($h, $method) = @_; + $h->trace_msg("Driver does not implement the $method method.\n"); + return; # empty list / undef + } + + # generic TIEHASH default methods: + sub FIRSTKEY { } + sub NEXTKEY { } + sub EXISTS { defined($_[0]->FETCH($_[1])) } # XXX undef? + sub CLEAR { Carp::carp "Can't CLEAR $_[0] (DBI)" } + + sub FETCH_many { # XXX should move to C one day + my $h = shift; + # scalar is needed to workaround drivers that return an empty list + # for some attributes + return map { scalar $h->FETCH($_) } @_; + } + + *dump_handle = \&DBI::dump_handle; + + sub install_method { + # special class method called directly by apps and/or drivers + # to install new methods into the DBI dispatcher + # DBD::Foo::db->install_method("foo_mumble", { usage => [...], options => '...' }); + my ($class, $method, $attr) = @_; + Carp::croak("Class '$class' must begin with DBD:: and end with ::db or ::st") + unless $class =~ /^DBD::(\w+)::(dr|db|st)$/; + my ($driver, $subtype) = ($1, $2); + Carp::croak("invalid method name '$method'") + unless $method =~ m/^([a-z]+_)\w+$/; + my $prefix = $1; + my $reg_info = $dbd_prefix_registry->{$prefix}; + Carp::carp("method name prefix '$prefix' is not associated with a registered driver") unless $reg_info; + + my $full_method = "DBI::${subtype}::$method"; + $DBI::installed_methods{$full_method} = $attr; + + my (undef, $filename, $line) = caller; + # XXX reformat $attr as needed for _install_method + my %attr = %{$attr||{}}; # copy so we can edit + DBI->_install_method("DBI::${subtype}::$method", "$filename at line $line", \%attr); + } + + sub parse_trace_flags { + my ($h, $spec) = @_; + my $level = 0; + my $flags = 0; + my @unknown; + for my $word (split /\s*[|&,]\s*/, $spec) { + if (DBI::looks_like_number($word) && $word <= 0xF && $word >= 0) { + $level = $word; + } elsif ($word eq 'ALL') { + $flags = 0x7FFFFFFF; # XXX last bit causes negative headaches + last; + } elsif (my $flag = $h->parse_trace_flag($word)) { + $flags |= $flag; + } + else { + push @unknown, $word; + } + } + if (@unknown && (ref $h ? $h->FETCH('Warn') : 1)) { + Carp::carp("$h->parse_trace_flags($spec) ignored unknown trace flags: ". + join(" ", map { DBI::neat($_) } @unknown)); + } + $flags |= $level; + return $flags; + } + + sub parse_trace_flag { + my ($h, $name) = @_; + # 0xddDDDDrL (driver, DBI, reserved, Level) + return 0x00000100 if $name eq 'SQL'; + return 0x00000200 if $name eq 'CON'; + return 0x00000400 if $name eq 'ENC'; + return 0x00000800 if $name eq 'DBD'; + return 0x00001000 if $name eq 'TXN'; + return; + } + + sub private_attribute_info { + return undef; + } + + sub visit_child_handles { + my ($h, $code, $info) = @_; + $info = {} if not defined $info; + for my $ch (@{ $h->{ChildHandles} || []}) { + next unless $ch; + my $child_info = $code->($ch, $info) + or next; + $ch->visit_child_handles($code, $child_info); + } + return $info; + } +} + + +{ package # hide from PAUSE + DBD::_::dr; # ====== DRIVER ====== + @DBD::_::dr::ISA = qw(DBD::_::common); + use strict; + + sub default_user { + my ($drh, $user, $pass, $attr) = @_; + $user = $ENV{DBI_USER} unless defined $user; + $pass = $ENV{DBI_PASS} unless defined $pass; + return ($user, $pass); + } + + sub connect { # normally overridden, but a handy default + my ($drh, $dsn, $user, $auth) = @_; + my ($this) = DBI::_new_dbh($drh, { + 'Name' => $dsn, + }); + # XXX debatable as there's no "server side" here + # (and now many uses would trigger warnings on DESTROY) + # $this->STORE(Active => 1); + # so drivers should set it in their own connect + $this; + } + + + sub connect_cached { + my $drh = shift; + my ($dsn, $user, $auth, $attr) = @_; + + my $cache = $drh->{CachedKids} ||= {}; + my $key = do { local $^W; + join "!\001", $dsn, $user, $auth, DBI::_concat_hash_sorted($attr, "=\001", ",\001", 0, 0) + }; + my $dbh = $cache->{$key}; + $drh->trace_msg(sprintf(" connect_cached: key '$key', cached dbh $dbh\n", DBI::neat($key), DBI::neat($dbh))) + if (($DBI::dbi_debug & 0xF) >= 4); + + my $cb = $attr->{Callbacks}; # take care not to autovivify + if ($dbh && $dbh->FETCH('Active') && eval { $dbh->ping }) { + # If the caller has provided a callback then call it + if ($cb and $cb = $cb->{"connect_cached.reused"}) { + local $_ = "connect_cached.reused"; + $cb->($dbh, $dsn, $user, $auth, $attr); + } + return $dbh; + } + + # If the caller has provided a callback then call it + if ($cb and $cb = $cb->{"connect_cached.new"}) { + local $_ = "connect_cached.new"; + $cb->($dbh, $dsn, $user, $auth, $attr); + } + + $dbh = $drh->connect(@_); + $cache->{$key} = $dbh; # replace prev entry, even if connect failed + return $dbh; + } + +} + + +{ package # hide from PAUSE + DBD::_::db; # ====== DATABASE ====== + @DBD::_::db::ISA = qw(DBD::_::common); + use strict; + + sub clone { + my ($old_dbh, $attr) = @_; + + my $closure = $old_dbh->{dbi_connect_closure} + or return $old_dbh->set_err($DBI::stderr, "Can't clone handle"); + + unless ($attr) { # XXX deprecated, caller should always pass a hash ref + # copy attributes visible in the attribute cache + keys %$old_dbh; # reset iterator + while ( my ($k, $v) = each %$old_dbh ) { + # ignore non-code refs, i.e., caches, handles, Err etc + next if ref $v && ref $v ne 'CODE'; # HandleError etc + $attr->{$k} = $v; + } + # explicitly set attributes which are unlikely to be in the + # attribute cache, i.e., boolean's and some others + $attr->{$_} = $old_dbh->FETCH($_) for (qw( + AutoCommit ChopBlanks InactiveDestroy AutoInactiveDestroy + LongTruncOk PrintError PrintWarn Profile RaiseError + ShowErrorStatement TaintIn TaintOut + )); + } + + # use Data::Dumper; warn Dumper([$old_dbh, $attr]); + my $new_dbh = &$closure($old_dbh, $attr); + unless ($new_dbh) { + # need to copy err/errstr from driver back into $old_dbh + my $drh = $old_dbh->{Driver}; + return $old_dbh->set_err($drh->err, $drh->errstr, $drh->state); + } + $new_dbh->{dbi_connect_closure} = $closure; + return $new_dbh; + } + + sub quote_identifier { + my ($dbh, @id) = @_; + my $attr = (@id > 3 && ref($id[-1])) ? pop @id : undef; + + my $info = $dbh->{dbi_quote_identifier_cache} ||= [ + $dbh->get_info(29) || '"', # SQL_IDENTIFIER_QUOTE_CHAR + $dbh->get_info(41) || '.', # SQL_CATALOG_NAME_SEPARATOR + $dbh->get_info(114) || 1, # SQL_CATALOG_LOCATION + ]; + + my $quote = $info->[0]; + foreach (@id) { # quote the elements + next unless defined; + s/$quote/$quote$quote/g; # escape embedded quotes + $_ = qq{$quote$_$quote}; + } + + # strip out catalog if present for special handling + my $catalog = (@id >= 3) ? shift @id : undef; + + # join the dots, ignoring any null/undef elements (ie schema) + my $quoted_id = join '.', grep { defined } @id; + + if ($catalog) { # add catalog correctly + $quoted_id = ($info->[2] == 2) # SQL_CL_END + ? $quoted_id . $info->[1] . $catalog + : $catalog . $info->[1] . $quoted_id; + } + return $quoted_id; + } + + sub quote { + my ($dbh, $str, $data_type) = @_; + + return "NULL" unless defined $str; + unless ($data_type) { + $str =~ s/'/''/g; # ISO SQL2 + return "'$str'"; + } + + my $dbi_literal_quote_cache = $dbh->{'dbi_literal_quote_cache'} ||= [ {} , {} ]; + my ($prefixes, $suffixes) = @$dbi_literal_quote_cache; + + my $lp = $prefixes->{$data_type}; + my $ls = $suffixes->{$data_type}; + + if ( ! defined $lp || ! defined $ls ) { + my $ti = $dbh->type_info($data_type); + $lp = $prefixes->{$data_type} = $ti ? $ti->{LITERAL_PREFIX} || "" : "'"; + $ls = $suffixes->{$data_type} = $ti ? $ti->{LITERAL_SUFFIX} || "" : "'"; + } + return $str unless $lp || $ls; # no quoting required + + # XXX don't know what the standard says about escaping + # in the 'general case' (where $lp != "'"). + # So we just do this and hope: + $str =~ s/$lp/$lp$lp/g + if $lp && $lp eq $ls && ($lp eq "'" || $lp eq '"'); + return "$lp$str$ls"; + } + + sub rows { -1 } # here so $DBI::rows 'works' after using $dbh + + sub do { + my($dbh, $statement, $attr, @params) = @_; + my $sth = $dbh->prepare($statement, $attr) or return undef; + $sth->execute(@params) or return undef; + my $rows = $sth->rows; + ($rows == 0) ? "0E0" : $rows; + } + + sub _do_selectrow { + my ($method, $dbh, $stmt, $attr, @bind) = @_; + my $sth = ((ref $stmt) ? $stmt : $dbh->prepare($stmt, $attr)) + or return; + $sth->execute(@bind) + or return; + my $row = $sth->$method() + and $sth->finish; + return $row; + } + + sub selectrow_hashref { return _do_selectrow('fetchrow_hashref', @_); } + + # XXX selectrow_array/ref also have C implementations in Driver.xst + sub selectrow_arrayref { return _do_selectrow('fetchrow_arrayref', @_); } + sub selectrow_array { + my $row = _do_selectrow('fetchrow_arrayref', @_) or return; + return $row->[0] unless wantarray; + return @$row; + } + + # XXX selectall_arrayref also has C implementation in Driver.xst + # which fallsback to this if a slice is given + sub selectall_arrayref { + my ($dbh, $stmt, $attr, @bind) = @_; + my $sth = (ref $stmt) ? $stmt : $dbh->prepare($stmt, $attr) + or return; + $sth->execute(@bind) || return; + my $slice = $attr->{Slice}; # typically undef, else hash or array ref + if (!$slice and $slice=$attr->{Columns}) { + if (ref $slice eq 'ARRAY') { # map col idx to perl array idx + $slice = [ @{$attr->{Columns}} ]; # take a copy + for (@$slice) { $_-- } + } + } + my $rows = $sth->fetchall_arrayref($slice, my $MaxRows = $attr->{MaxRows}); + $sth->finish if defined $MaxRows; + return $rows; + } + + sub selectall_hashref { + my ($dbh, $stmt, $key_field, $attr, @bind) = @_; + my $sth = (ref $stmt) ? $stmt : $dbh->prepare($stmt, $attr); + return unless $sth; + $sth->execute(@bind) || return; + return $sth->fetchall_hashref($key_field); + } + + sub selectcol_arrayref { + my ($dbh, $stmt, $attr, @bind) = @_; + my $sth = (ref $stmt) ? $stmt : $dbh->prepare($stmt, $attr); + return unless $sth; + $sth->execute(@bind) || return; + my @columns = ($attr->{Columns}) ? @{$attr->{Columns}} : (1); + my @values = (undef) x @columns; + my $idx = 0; + for (@columns) { + $sth->bind_col($_, \$values[$idx++]) || return; + } + my @col; + if (my $max = $attr->{MaxRows}) { + push @col, @values while 0 < $max-- && $sth->fetch; + } + else { + push @col, @values while $sth->fetch; + } + return \@col; + } + + sub prepare_cached { + my ($dbh, $statement, $attr, $if_active) = @_; + + # Needs support at dbh level to clear cache before complaining about + # active children. The XS template code does this. Drivers not using + # the template must handle clearing the cache themselves. + my $cache = $dbh->{CachedKids} ||= {}; + my $key = do { local $^W; + join "!\001", $statement, DBI::_concat_hash_sorted($attr, "=\001", ",\001", 0, 0) + }; + my $sth = $cache->{$key}; + + if ($sth) { + return $sth unless $sth->FETCH('Active'); + Carp::carp("prepare_cached($statement) statement handle $sth still Active") + unless ($if_active ||= 0); + $sth->finish if $if_active <= 1; + return $sth if $if_active <= 2; + } + + $sth = $dbh->prepare($statement, $attr); + $cache->{$key} = $sth if $sth; + + return $sth; + } + + sub ping { + my $dbh = shift; + $dbh->_not_impl('ping'); + # "0 but true" is a special kind of true 0 that is used here so + # applications can check if the ping was a real ping or not + ($dbh->FETCH('Active')) ? "0 but true" : 0; + } + + sub begin_work { + my $dbh = shift; + return $dbh->set_err($DBI::stderr, "Already in a transaction") + unless $dbh->FETCH('AutoCommit'); + $dbh->STORE('AutoCommit', 0); # will croak if driver doesn't support it + $dbh->STORE('BegunWork', 1); # trigger post commit/rollback action + return 1; + } + + sub primary_key { + my ($dbh, @args) = @_; + my $sth = $dbh->primary_key_info(@args) or return; + my ($row, @col); + push @col, $row->[3] while ($row = $sth->fetch); + Carp::croak("primary_key method not called in list context") + unless wantarray; # leave us some elbow room + return @col; + } + + sub tables { + my ($dbh, @args) = @_; + my $sth = $dbh->table_info(@args[0,1,2,3,4]) or return; + my $tables = $sth->fetchall_arrayref or return; + my @tables; + if ($dbh->get_info(29)) { # SQL_IDENTIFIER_QUOTE_CHAR + @tables = map { $dbh->quote_identifier( @{$_}[0,1,2] ) } @$tables; + } + else { # temporary old style hack (yeach) + @tables = map { + my $name = $_->[2]; + if ($_->[1]) { + my $schema = $_->[1]; + # a sad hack (mostly for Informix I recall) + my $quote = ($schema eq uc($schema)) ? '' : '"'; + $name = "$quote$schema$quote.$name" + } + $name; + } @$tables; + } + return @tables; + } + + sub type_info { # this should be sufficient for all drivers + my ($dbh, $data_type) = @_; + my $idx_hash; + my $tia = $dbh->{dbi_type_info_row_cache}; + if ($tia) { + $idx_hash = $dbh->{dbi_type_info_idx_cache}; + } + else { + my $temp = $dbh->type_info_all; + return unless $temp && @$temp; + # we cache here because type_info_all may be expensive to call + # (and we take a copy so the following shift can't corrupt + # the data that may be returned by future calls to type_info_all) + $tia = $dbh->{dbi_type_info_row_cache} = [ @$temp ]; + $idx_hash = $dbh->{dbi_type_info_idx_cache} = shift @$tia; + } + + my $dt_idx = $idx_hash->{DATA_TYPE} || $idx_hash->{data_type}; + Carp::croak("type_info_all returned non-standard DATA_TYPE index value ($dt_idx != 1)") + if $dt_idx && $dt_idx != 1; + + # --- simple DATA_TYPE match filter + my @ti; + my @data_type_list = (ref $data_type) ? @$data_type : ($data_type); + foreach $data_type (@data_type_list) { + if (defined($data_type) && $data_type != DBI::SQL_ALL_TYPES()) { + push @ti, grep { $_->[$dt_idx] == $data_type } @$tia; + } + else { # SQL_ALL_TYPES + push @ti, @$tia; + } + last if @ti; # found at least one match + } + + # --- format results into list of hash refs + my $idx_fields = keys %$idx_hash; + my @idx_names = map { uc($_) } keys %$idx_hash; + my @idx_values = values %$idx_hash; + Carp::croak "type_info_all result has $idx_fields keys but ".(@{$ti[0]})." fields" + if @ti && @{$ti[0]} != $idx_fields; + my @out = map { + my %h; @h{@idx_names} = @{$_}[ @idx_values ]; \%h; + } @ti; + return $out[0] unless wantarray; + return @out; + } + + sub data_sources { + my ($dbh, @other) = @_; + my $drh = $dbh->{Driver}; # XXX proxy issues? + return $drh->data_sources(@other); + } + +} + + +{ package # hide from PAUSE + DBD::_::st; # ====== STATEMENT ====== + @DBD::_::st::ISA = qw(DBD::_::common); + use strict; + + sub bind_param { Carp::croak("Can't bind_param, not implement by driver") } + +# +# ******************************************************** +# +# BEGIN ARRAY BINDING +# +# Array binding support for drivers which don't support +# array binding, but have sufficient interfaces to fake it. +# NOTE: mixing scalars and arrayrefs requires using bind_param_array +# for *all* params...unless we modify bind_param for the default +# case... +# +# 2002-Apr-10 D. Arnold + + sub bind_param_array { + my $sth = shift; + my ($p_id, $value_array, $attr) = @_; + + return $sth->set_err($DBI::stderr, "Value for parameter $p_id must be a scalar or an arrayref, not a ".ref($value_array)) + if defined $value_array and ref $value_array and ref $value_array ne 'ARRAY'; + + return $sth->set_err($DBI::stderr, "Can't use named placeholder '$p_id' for non-driver supported bind_param_array") + unless DBI::looks_like_number($p_id); # because we rely on execute(@ary) here + + return $sth->set_err($DBI::stderr, "Placeholder '$p_id' is out of range") + if $p_id <= 0; # can't easily/reliably test for too big + + # get/create arrayref to hold params + my $hash_of_arrays = $sth->{ParamArrays} ||= { }; + + # If the bind has attribs then we rely on the driver conforming to + # the DBI spec in that a single bind_param() call with those attribs + # makes them 'sticky' and apply to all later execute(@values) calls. + # Since we only call bind_param() if we're given attribs then + # applications using drivers that don't support bind_param can still + # use bind_param_array() so long as they don't pass any attribs. + + $$hash_of_arrays{$p_id} = $value_array; + return $sth->bind_param($p_id, undef, $attr) + if $attr; + 1; + } + + sub bind_param_inout_array { + my $sth = shift; + # XXX not supported so we just call bind_param_array instead + # and then return an error + my ($p_num, $value_array, $attr) = @_; + $sth->bind_param_array($p_num, $value_array, $attr); + return $sth->set_err($DBI::stderr, "bind_param_inout_array not supported"); + } + + sub bind_columns { + my $sth = shift; + my $fields = $sth->FETCH('NUM_OF_FIELDS') || 0; + if ($fields <= 0 && !$sth->{Active}) { + return $sth->set_err($DBI::stderr, "Statement has no result columns to bind" + ." (perhaps you need to successfully call execute first)"); + } + # Backwards compatibility for old-style call with attribute hash + # ref as first arg. Skip arg if undef or a hash ref. + my $attr; + $attr = shift if !defined $_[0] or ref($_[0]) eq 'HASH'; + + my $idx = 0; + $sth->bind_col(++$idx, shift, $attr) or return + while (@_ and $idx < $fields); + + return $sth->set_err($DBI::stderr, "bind_columns called with ".($idx+@_)." values but $fields are needed") + if @_ or $idx != $fields; + + return 1; + } + + sub execute_array { + my $sth = shift; + my ($attr, @array_of_arrays) = @_; + my $NUM_OF_PARAMS = $sth->FETCH('NUM_OF_PARAMS'); # may be undef at this point + + # get tuple status array or hash attribute + my $tuple_sts = $attr->{ArrayTupleStatus}; + return $sth->set_err($DBI::stderr, "ArrayTupleStatus attribute must be an arrayref") + if $tuple_sts and ref $tuple_sts ne 'ARRAY'; + + # bind all supplied arrays + if (@array_of_arrays) { + $sth->{ParamArrays} = { }; # clear out old params + return $sth->set_err($DBI::stderr, + @array_of_arrays." bind values supplied but $NUM_OF_PARAMS expected") + if defined ($NUM_OF_PARAMS) && @array_of_arrays != $NUM_OF_PARAMS; + $sth->bind_param_array($_, $array_of_arrays[$_-1]) or return + foreach (1..@array_of_arrays); + } + + my $fetch_tuple_sub; + + if ($fetch_tuple_sub = $attr->{ArrayTupleFetch}) { # fetch on demand + + return $sth->set_err($DBI::stderr, + "Can't use both ArrayTupleFetch and explicit bind values") + if @array_of_arrays; # previous bind_param_array calls will simply be ignored + + if (UNIVERSAL::isa($fetch_tuple_sub,'DBI::st')) { + my $fetch_sth = $fetch_tuple_sub; + return $sth->set_err($DBI::stderr, + "ArrayTupleFetch sth is not Active, need to execute() it first") + unless $fetch_sth->{Active}; + # check column count match to give more friendly message + my $NUM_OF_FIELDS = $fetch_sth->{NUM_OF_FIELDS}; + return $sth->set_err($DBI::stderr, + "$NUM_OF_FIELDS columns from ArrayTupleFetch sth but $NUM_OF_PARAMS expected") + if defined($NUM_OF_FIELDS) && defined($NUM_OF_PARAMS) + && $NUM_OF_FIELDS != $NUM_OF_PARAMS; + $fetch_tuple_sub = sub { $fetch_sth->fetchrow_arrayref }; + } + elsif (!UNIVERSAL::isa($fetch_tuple_sub,'CODE')) { + return $sth->set_err($DBI::stderr, "ArrayTupleFetch '$fetch_tuple_sub' is not a code ref or statement handle"); + } + + } + else { + my $NUM_OF_PARAMS_given = keys %{ $sth->{ParamArrays} || {} }; + return $sth->set_err($DBI::stderr, + "$NUM_OF_PARAMS_given bind values supplied but $NUM_OF_PARAMS expected") + if defined($NUM_OF_PARAMS) && $NUM_OF_PARAMS != $NUM_OF_PARAMS_given; + + # get the length of a bound array + my $maxlen; + my %hash_of_arrays = %{$sth->{ParamArrays}}; + foreach (keys(%hash_of_arrays)) { + my $ary = $hash_of_arrays{$_}; + next unless ref $ary eq 'ARRAY'; + $maxlen = @$ary if !$maxlen || @$ary > $maxlen; + } + # if there are no arrays then execute scalars once + $maxlen = 1 unless defined $maxlen; + my @bind_ids = 1..keys(%hash_of_arrays); + + my $tuple_idx = 0; + $fetch_tuple_sub = sub { + return if $tuple_idx >= $maxlen; + my @tuple = map { + my $a = $hash_of_arrays{$_}; + ref($a) ? $a->[$tuple_idx] : $a + } @bind_ids; + ++$tuple_idx; + return \@tuple; + }; + } + # pass thru the callers scalar or list context + return $sth->execute_for_fetch($fetch_tuple_sub, $tuple_sts); + } + + sub execute_for_fetch { + my ($sth, $fetch_tuple_sub, $tuple_status) = @_; + # start with empty status array + ($tuple_status) ? @$tuple_status = () : $tuple_status = []; + + my $rc_total = 0; + my $err_count; + while ( my $tuple = &$fetch_tuple_sub() ) { + if ( my $rc = $sth->execute(@$tuple) ) { + push @$tuple_status, $rc; + $rc_total = ($rc >= 0 && $rc_total >= 0) ? $rc_total + $rc : -1; + } + else { + $err_count++; + push @$tuple_status, [ $sth->err, $sth->errstr, $sth->state ]; + # XXX drivers implementing execute_for_fetch could opt to "last;" here + # if they know the error code means no further executes will work. + } + } + my $tuples = @$tuple_status; + return $sth->set_err($DBI::stderr, "executing $tuples generated $err_count errors") + if $err_count; + $tuples ||= "0E0"; + return $tuples unless wantarray; + return ($tuples, $rc_total); + } + + + sub fetchall_arrayref { # ALSO IN Driver.xst + my ($sth, $slice, $max_rows) = @_; + + # when batch fetching with $max_rows were very likely to try to + # fetch the 'next batch' after the previous batch returned + # <=$max_rows. So don't treat that as an error. + return undef if $max_rows and not $sth->FETCH('Active'); + + my $mode = ref($slice) || 'ARRAY'; + my @rows; + + if ($mode eq 'ARRAY') { + my $row; + # we copy the array here because fetch (currently) always + # returns the same array ref. XXX + if ($slice && @$slice) { + $max_rows = -1 unless defined $max_rows; + push @rows, [ @{$row}[ @$slice] ] + while($max_rows-- and $row = $sth->fetch); + } + elsif (defined $max_rows) { + push @rows, [ @$row ] + while($max_rows-- and $row = $sth->fetch); + } + else { + push @rows, [ @$row ] while($row = $sth->fetch); + } + return \@rows + } + + my %row; + if ($mode eq 'REF' && ref($$slice) eq 'HASH') { # \{ $idx => $name } + keys %$$slice; # reset the iterator + while ( my ($idx, $name) = each %$$slice ) { + $sth->bind_col($idx+1, \$row{$name}); + } + } + elsif ($mode eq 'HASH') { + if (keys %$slice) { + keys %$slice; # reset the iterator + my $name2idx = $sth->FETCH('NAME_lc_hash'); + while ( my ($name, $unused) = each %$slice ) { + my $idx = $name2idx->{lc $name}; + return $sth->set_err($DBI::stderr, "Invalid column name '$name' for slice") + if not defined $idx; + $sth->bind_col($idx+1, \$row{$name}); + } + } + else { + $sth->bind_columns( \( @row{ @{$sth->FETCH($sth->FETCH('FetchHashKeyName')) } } ) ); + } + } + else { + return $sth->set_err($DBI::stderr, "fetchall_arrayref($mode) invalid"); + } + + if (not defined $max_rows) { + push @rows, { %row } while ($sth->fetch); # full speed ahead! + } + else { + push @rows, { %row } while ($max_rows-- and $sth->fetch); + } + + return \@rows; + } + + sub fetchall_hashref { + my ($sth, $key_field) = @_; + + my $hash_key_name = $sth->{FetchHashKeyName} || 'NAME'; + my $names_hash = $sth->FETCH("${hash_key_name}_hash"); + my @key_fields = (ref $key_field) ? @$key_field : ($key_field); + my @key_indexes; + my $num_of_fields = $sth->FETCH('NUM_OF_FIELDS'); + foreach (@key_fields) { + my $index = $names_hash->{$_}; # perl index not column + $index = $_ - 1 if !defined $index && DBI::looks_like_number($_) && $_>=1 && $_ <= $num_of_fields; + return $sth->set_err($DBI::stderr, "Field '$_' does not exist (not one of @{[keys %$names_hash]})") + unless defined $index; + push @key_indexes, $index; + } + my $rows = {}; + my $NAME = $sth->FETCH($hash_key_name); + my @row = (undef) x $num_of_fields; + $sth->bind_columns(\(@row)); + while ($sth->fetch) { + my $ref = $rows; + $ref = $ref->{$row[$_]} ||= {} for @key_indexes; + @{$ref}{@$NAME} = @row; + } + return $rows; + } + + *dump_results = \&DBI::dump_results; + + sub blob_copy_to_file { # returns length or undef on error + my($self, $field, $filename_or_handleref, $blocksize) = @_; + my $fh = $filename_or_handleref; + my($len, $buf) = (0, ""); + $blocksize ||= 512; # not too ambitious + local(*FH); + unless(ref $fh) { + open(FH, ">$fh") || return undef; + $fh = \*FH; + } + while(defined($self->blob_read($field, $len, $blocksize, \$buf))) { + print $fh $buf; + $len += length $buf; + } + close(FH); + $len; + } + + sub more_results { + shift->{syb_more_results}; # handy grandfathering + } + +} + +unless ($DBI::PurePerl) { # See install_driver + { @DBD::_mem::dr::ISA = qw(DBD::_mem::common); } + { @DBD::_mem::db::ISA = qw(DBD::_mem::common); } + { @DBD::_mem::st::ISA = qw(DBD::_mem::common); } + # DBD::_mem::common::DESTROY is implemented in DBI.xs +} + +1; +__END__ + +=head1 DESCRIPTION + +The DBI is a database access module for the Perl programming language. It defines +a set of methods, variables, and conventions that provide a consistent +database interface, independent of the actual database being used. + +It is important to remember that the DBI is just an interface. +The DBI is a layer +of "glue" between an application and one or more database I<driver> +modules. It is the driver modules which do most of the real work. The DBI +provides a standard interface and framework for the drivers to operate +within. + + +=head2 Architecture of a DBI Application + + |<- Scope of DBI ->| + .-. .--------------. .-------------. + .-------. | |---| XYZ Driver |---| XYZ Engine | + | Perl | | | `--------------' `-------------' + | script| |A| |D| .--------------. .-------------. + | using |--|P|--|B|---|Oracle Driver |---|Oracle Engine| + | DBI | |I| |I| `--------------' `-------------' + | API | | |... + |methods| | |... Other drivers + `-------' | |... + `-' + +The API, or Application Programming Interface, defines the +call interface and variables for Perl scripts to use. The API +is implemented by the Perl DBI extension. + +The DBI "dispatches" the method calls to the appropriate driver for +actual execution. The DBI is also responsible for the dynamic loading +of drivers, error checking and handling, providing default +implementations for methods, and many other non-database specific duties. + +Each driver +contains implementations of the DBI methods using the +private interface functions of the corresponding database engine. Only authors +of sophisticated/multi-database applications or generic library +functions need be concerned with drivers. + +=head2 Notation and Conventions + +The following conventions are used in this document: + + $dbh Database handle object + $sth Statement handle object + $drh Driver handle object (rarely seen or used in applications) + $h Any of the handle types above ($dbh, $sth, or $drh) + $rc General Return Code (boolean: true=ok, false=error) + $rv General Return Value (typically an integer) + @ary List of values returned from the database, typically a row of data + $rows Number of rows processed (if available, else -1) + $fh A filehandle + undef NULL values are represented by undefined values in Perl + \%attr Reference to a hash of attribute values passed to methods + +Note that Perl will automatically destroy database and statement handle objects +if all references to them are deleted. + + +=head2 Outline Usage + +To use DBI, +first you need to load the DBI module: + + use DBI; + use strict; + +(The C<use strict;> isn't required but is strongly recommended.) + +Then you need to L</connect> to your data source and get a I<handle> for that +connection: + + $dbh = DBI->connect($dsn, $user, $password, + { RaiseError => 1, AutoCommit => 0 }); + +Since connecting can be expensive, you generally just connect at the +start of your program and disconnect at the end. + +Explicitly defining the required C<AutoCommit> behaviour is strongly +recommended and may become mandatory in a later version. This +determines whether changes are automatically committed to the +database when executed, or need to be explicitly committed later. + +The DBI allows an application to "prepare" statements for later +execution. A prepared statement is identified by a statement handle +held in a Perl variable. +We'll call the Perl variable C<$sth> in our examples. + +The typical method call sequence for a C<SELECT> statement is: + + prepare, + execute, fetch, fetch, ... + execute, fetch, fetch, ... + execute, fetch, fetch, ... + +for example: + + $sth = $dbh->prepare("SELECT foo, bar FROM table WHERE baz=?"); + + $sth->execute( $baz ); + + while ( @row = $sth->fetchrow_array ) { + print "@row\n"; + } + +The typical method call sequence for a I<non>-C<SELECT> statement is: + + prepare, + execute, + execute, + execute. + +for example: + + $sth = $dbh->prepare("INSERT INTO table(foo,bar,baz) VALUES (?,?,?)"); + + while(<CSV>) { + chomp; + my ($foo,$bar,$baz) = split /,/; + $sth->execute( $foo, $bar, $baz ); + } + +The C<do()> method can be used for non repeated I<non>-C<SELECT> statement +(or with drivers that don't support placeholders): + + $rows_affected = $dbh->do("UPDATE your_table SET foo = foo + 1"); + +To commit your changes to the database (when L</AutoCommit> is off): + + $dbh->commit; # or call $dbh->rollback; to undo changes + +Finally, when you have finished working with the data source, you should +L</disconnect> from it: + + $dbh->disconnect; + + +=head2 General Interface Rules & Caveats + +The DBI does not have a concept of a "current session". Every session +has a handle object (i.e., a C<$dbh>) returned from the C<connect> method. +That handle object is used to invoke database related methods. + +Most data is returned to the Perl script as strings. (Null values are +returned as C<undef>.) This allows arbitrary precision numeric data to be +handled without loss of accuracy. Beware that Perl may not preserve +the same accuracy when the string is used as a number. + +Dates and times are returned as character strings in the current +default format of the corresponding database engine. Time zone effects +are database/driver dependent. + +Perl supports binary data in Perl strings, and the DBI will pass binary +data to and from the driver without change. It is up to the driver +implementors to decide how they wish to handle such binary data. + +Perl supports two kinds of strings: Unicode (utf8 internally) and non-Unicode +(defaults to iso-8859-1 if forced to assume an encoding). Drivers should +accept both kinds of strings and, if required, convert them to the character +set of the database being used. Similarly, when fetching from the database +character data that isn't iso-8859-1 the driver should convert it into utf8. + +Multiple SQL statements may not be combined in a single statement +handle (C<$sth>), although some databases and drivers do support this +(notably Sybase and SQL Server). + +Non-sequential record reads are not supported in this version of the DBI. +In other words, records can only be fetched in the order that the +database returned them, and once fetched they are forgotten. + +Positioned updates and deletes are not directly supported by the DBI. +See the description of the C<CursorName> attribute for an alternative. + +Individual driver implementors are free to provide any private +functions and/or handle attributes that they feel are useful. +Private driver functions can be invoked using the DBI C<func()> method. +Private driver attributes are accessed just like standard attributes. + +Many methods have an optional C<\%attr> parameter which can be used to +pass information to the driver implementing the method. Except where +specifically documented, the C<\%attr> parameter can only be used to pass +driver specific hints. In general, you can ignore C<\%attr> parameters +or pass it as C<undef>. + + +=head2 Naming Conventions and Name Space + +The DBI package and all packages below it (C<DBI::*>) are reserved for +use by the DBI. Extensions and related modules use the C<DBIx::> +namespace (see L<http://www.perl.com/CPAN/modules/by-module/DBIx/>). +Package names beginning with C<DBD::> are reserved for use +by DBI database drivers. All environment variables used by the DBI +or by individual DBDs begin with "C<DBI_>" or "C<DBD_>". + +The letter case used for attribute names is significant and plays an +important part in the portability of DBI scripts. The case of the +attribute name is used to signify who defined the meaning of that name +and its values. + + Case of name Has a meaning defined by + ------------ ------------------------ + UPPER_CASE Standards, e.g., X/Open, ISO SQL92 etc (portable) + MixedCase DBI API (portable), underscores are not used. + lower_case Driver or database engine specific (non-portable) + +It is of the utmost importance that Driver developers only use +lowercase attribute names when defining private attributes. Private +attribute names must be prefixed with the driver name or suitable +abbreviation (e.g., "C<ora_>" for Oracle, "C<ing_>" for Ingres, etc). + + +=head2 SQL - A Query Language + +Most DBI drivers require applications to use a dialect of SQL +(Structured Query Language) to interact with the database engine. +The L</"Standards Reference Information"> section provides links +to useful information about SQL. + +The DBI itself does not mandate or require any particular language to +be used; it is language independent. In ODBC terms, the DBI is in +"pass-thru" mode, although individual drivers might not be. The only requirement +is that queries and other statements must be expressed as a single +string of characters passed as the first argument to the L</prepare> or +L</do> methods. + +For an interesting diversion on the I<real> history of RDBMS and SQL, +from the people who made it happen, see: + + http://www.mcjones.org/System_R/SQL_Reunion_95/sqlr95.html + +Follow the "Full Contents" then "Intergalactic dataspeak" links for the +SQL history. + +=head2 Placeholders and Bind Values + +Some drivers support placeholders and bind values. +I<Placeholders>, also called parameter markers, are used to indicate +values in a database statement that will be supplied later, +before the prepared statement is executed. For example, an application +might use the following to insert a row of data into the SALES table: + + INSERT INTO sales (product_code, qty, price) VALUES (?, ?, ?) + +or the following, to select the description for a product: + + SELECT description FROM products WHERE product_code = ? + +The C<?> characters are the placeholders. The association of actual +values with placeholders is known as I<binding>, and the values are +referred to as I<bind values>. +Note that the C<?> is not enclosed in quotation marks, even when the +placeholder represents a string. + +Some drivers also allow placeholders like C<:>I<name> and C<:>I<N> (e.g., +C<:1>, C<:2>, and so on) in addition to C<?>, but their use is not portable. + +If the C<:>I<N> form of placeholder is supported by the driver you're using, +then you should be able to use either L</bind_param> or L</execute> to bind +values. Check your driver documentation. + +With most drivers, placeholders can't be used for any element of a +statement that would prevent the database server from validating the +statement and creating a query execution plan for it. For example: + + "SELECT name, age FROM ?" # wrong (will probably fail) + "SELECT name, ? FROM people" # wrong (but may not 'fail') + +Also, placeholders can only represent single scalar values. +For example, the following +statement won't work as expected for more than one value: + + "SELECT name, age FROM people WHERE name IN (?)" # wrong + "SELECT name, age FROM people WHERE name IN (?,?)" # two names + +When using placeholders with the SQL C<LIKE> qualifier, you must +remember that the placeholder substitutes for the whole string. +So you should use "C<... LIKE ? ...>" and include any wildcard +characters in the value that you bind to the placeholder. + +B<NULL Values> + +Undefined values, or C<undef>, are used to indicate NULL values. +You can insert and update columns with a NULL value as you would a +non-NULL value. These examples insert and update the column +C<age> with a NULL value: + + $sth = $dbh->prepare(qq{ + INSERT INTO people (fullname, age) VALUES (?, ?) + }); + $sth->execute("Joe Bloggs", undef); + + $sth = $dbh->prepare(qq{ + UPDATE people SET age = ? WHERE fullname = ? + }); + $sth->execute(undef, "Joe Bloggs"); + +However, care must be taken when trying to use NULL values in a +C<WHERE> clause. Consider: + + SELECT fullname FROM people WHERE age = ? + +Binding an C<undef> (NULL) to the placeholder will I<not> select rows +which have a NULL C<age>! At least for database engines that +conform to the SQL standard. Refer to the SQL manual for your database +engine or any SQL book for the reasons for this. To explicitly select +NULLs you have to say "C<WHERE age IS NULL>". + +A common issue is to have a code fragment handle a value that could be +either C<defined> or C<undef> (non-NULL or NULL) at runtime. +A simple technique is to prepare the appropriate statement as needed, +and substitute the placeholder for non-NULL cases: + + $sql_clause = defined $age? "age = ?" : "age IS NULL"; + $sth = $dbh->prepare(qq{ + SELECT fullname FROM people WHERE $sql_clause + }); + $sth->execute(defined $age ? $age : ()); + +The following technique illustrates qualifying a C<WHERE> clause with +several columns, whose associated values (C<defined> or C<undef>) are +in a hash %h: + + for my $col ("age", "phone", "email") { + if (defined $h{$col}) { + push @sql_qual, "$col = ?"; + push @sql_bind, $h{$col}; + } + else { + push @sql_qual, "$col IS NULL"; + } + } + $sql_clause = join(" AND ", @sql_qual); + $sth = $dbh->prepare(qq{ + SELECT fullname FROM people WHERE $sql_clause + }); + $sth->execute(@sql_bind); + +The techniques above call prepare for the SQL statement with each call to +execute. Because calls to prepare() can be expensive, performance +can suffer when an application iterates many times over statements +like the above. + +A better solution is a single C<WHERE> clause that supports both +NULL and non-NULL comparisons. Its SQL statement would need to be +prepared only once for all cases, thus improving performance. +Several examples of C<WHERE> clauses that support this are presented +below. But each example lacks portability, robustness, or simplicity. +Whether an example is supported on your database engine depends on +what SQL extensions it provides, and where it supports the C<?> +placeholder in a statement. + + 0) age = ? + 1) NVL(age, xx) = NVL(?, xx) + 2) ISNULL(age, xx) = ISNULL(?, xx) + 3) DECODE(age, ?, 1, 0) = 1 + 4) age = ? OR (age IS NULL AND ? IS NULL) + 5) age = ? OR (age IS NULL AND SP_ISNULL(?) = 1) + 6) age = ? OR (age IS NULL AND ? = 1) + +Statements formed with the above C<WHERE> clauses require execute +statements as follows. The arguments are required, whether their +values are C<defined> or C<undef>. + + 0,1,2,3) $sth->execute($age); + 4,5) $sth->execute($age, $age); + 6) $sth->execute($age, defined($age) ? 0 : 1); + +Example 0 should not work (as mentioned earlier), but may work on +a few database engines anyway (e.g. Sybase). Example 0 is part +of examples 4, 5, and 6, so if example 0 works, these other +examples may work, even if the engine does not properly support +the right hand side of the C<OR> expression. + +Examples 1 and 2 are not robust: they require that you provide a +valid column value xx (e.g. '~') which is not present in any row. +That means you must have some notion of what data won't be stored +in the column, and expect clients to adhere to that. + +Example 5 requires that you provide a stored procedure (SP_ISNULL +in this example) that acts as a function: it checks whether a value +is null, and returns 1 if it is, or 0 if not. + +Example 6, the least simple, is probably the most portable, i.e., it +should work with with most, if not all, database engines. + +Here is a table that indicates which examples above are known to +work on various database engines: + + -----Examples------ + 0 1 2 3 4 5 6 + - - - - - - - + Oracle 9 N Y N Y Y ? Y + Informix IDS 9 N N N Y N Y Y + MS SQL N N Y N Y ? Y + Sybase Y N N N N N Y + AnyData,DBM,CSV Y N N N Y Y* Y + SQLite 3.3 N N N N Y N N + MSAccess N N N N Y N Y + +* Works only because Example 0 works. + +DBI provides a sample perl script that will test the examples above +on your database engine and tell you which ones work. It is located +in the F<ex/> subdirectory of the DBI source distribution, or here: +L<http://svn.perl.org/modules/dbi/trunk/ex/perl_dbi_nulls_test.pl> +Please use the script to help us fill-in and maintain this table. + +B<Performance> + +Without using placeholders, the insert statement shown previously would have to +contain the literal values to be inserted and would have to be +re-prepared and re-executed for each row. With placeholders, the insert +statement only needs to be prepared once. The bind values for each row +can be given to the C<execute> method each time it's called. By avoiding +the need to re-prepare the statement for each row, the application +typically runs many times faster. Here's an example: + + my $sth = $dbh->prepare(q{ + INSERT INTO sales (product_code, qty, price) VALUES (?, ?, ?) + }) or die $dbh->errstr; + while (<>) { + chomp; + my ($product_code, $qty, $price) = split /,/; + $sth->execute($product_code, $qty, $price) or die $dbh->errstr; + } + $dbh->commit or die $dbh->errstr; + +See L</execute> and L</bind_param> for more details. + +The C<q{...}> style quoting used in this example avoids clashing with +quotes that may be used in the SQL statement. Use the double-quote like +C<qq{...}> operator if you want to interpolate variables into the string. +See L<perlop/"Quote and Quote-like Operators"> for more details. + +See also the L</bind_columns> method, which is used to associate Perl +variables with the output columns of a C<SELECT> statement. + +=head1 THE DBI PACKAGE AND CLASS + +In this section, we cover the DBI class methods, utility functions, +and the dynamic attributes associated with generic DBI handles. + +=head2 DBI Constants + +Constants representing the values of the SQL standard types can be +imported individually by name, or all together by importing the +special C<:sql_types> tag. + +The names and values of all the defined SQL standard types can be +produced like this: + + foreach (@{ $DBI::EXPORT_TAGS{sql_types} }) { + printf "%s=%d\n", $_, &{"DBI::$_"}; + } + +These constants are defined by SQL/CLI, ODBC or both. +C<SQL_BIGINT> is (currently) omitted, because SQL/CLI and ODBC provide +conflicting codes. + +See the L</type_info>, L</type_info_all>, and L</bind_param> methods +for possible uses. + +Note that just because the DBI defines a named constant for a given +data type doesn't mean that drivers will support that data type. + + +=head2 DBI Class Methods + +The following methods are provided by the DBI class: + +=head3 C<parse_dsn> + + ($scheme, $driver, $attr_string, $attr_hash, $driver_dsn) = DBI->parse_dsn($dsn) + or die "Can't parse DBI DSN '$dsn'"; + +Breaks apart a DBI Data Source Name (DSN) and returns the individual +parts. If $dsn doesn't contain a valid DSN then parse_dsn() returns +an empty list. + +$scheme is the first part of the DSN and is currently always 'dbi'. +$driver is the driver name, possibly defaulted to $ENV{DBI_DRIVER}, +and may be undefined. $attr_string is the contents of the optional attribute +string, which may be undefined. If $attr_string is not empty then $attr_hash +is a reference to a hash containing the parsed attribute names and values. +$driver_dsn is the last part of the DBI DSN string. For example: + + ($scheme, $driver, $attr_string, $attr_hash, $driver_dsn) + = DBI->parse_dsn("DBI:MyDriver(RaiseError=>1):db=test;port=42"); + $scheme = 'dbi'; + $driver = 'MyDriver'; + $attr_string = 'RaiseError=>1'; + $attr_hash = { 'RaiseError' => '1' }; + $driver_dsn = 'db=test;port=42'; + +The parse_dsn() method was added in DBI 1.43. + +=head3 C<connect> + + $dbh = DBI->connect($data_source, $username, $password) + or die $DBI::errstr; + $dbh = DBI->connect($data_source, $username, $password, \%attr) + or die $DBI::errstr; + +Establishes a database connection, or session, to the requested C<$data_source>. +Returns a database handle object if the connection succeeds. Use +C<$dbh-E<gt>disconnect> to terminate the connection. + +If the connect fails (see below), it returns C<undef> and sets both C<$DBI::err> +and C<$DBI::errstr>. (It does I<not> explicitly set C<$!>.) You should generally +test the return status of C<connect> and C<print $DBI::errstr> if it has failed. + +Multiple simultaneous connections to multiple databases through multiple +drivers can be made via the DBI. Simply make one C<connect> call for each +database and keep a copy of each returned database handle. + +The C<$data_source> value must begin with "C<dbi:>I<driver_name>C<:>". +The I<driver_name> specifies the driver that will be used to make the +connection. (Letter case is significant.) + +As a convenience, if the C<$data_source> parameter is undefined or empty, +the DBI will substitute the value of the environment variable C<DBI_DSN>. +If just the I<driver_name> part is empty (i.e., the C<$data_source> +prefix is "C<dbi::>"), the environment variable C<DBI_DRIVER> is +used. If neither variable is set, then C<connect> dies. + +Examples of C<$data_source> values are: + + dbi:DriverName:database_name + dbi:DriverName:database_name@hostname:port + dbi:DriverName:database=database_name;host=hostname;port=port + +There is I<no standard> for the text following the driver name. Each +driver is free to use whatever syntax it wants. The only requirement the +DBI makes is that all the information is supplied in a single string. +You must consult the documentation for the drivers you are using for a +description of the syntax they require. + +It is recommended that drivers support the ODBC style, shown in the +last example above. It is also recommended that that they support the +three common names 'C<host>', 'C<port>', and 'C<database>' (plus 'C<db>' +as an alias for C<database>). This simplifies automatic construction +of basic DSNs: C<"dbi:$driver:database=$db;host=$host;port=$port">. +Drivers should aim to 'do something reasonable' when given a DSN +in this form, but if any part is meaningless for that driver (such +as 'port' for Informix) it should generate an error if that part +is not empty. + +If the environment variable C<DBI_AUTOPROXY> is defined (and the +driver in C<$data_source> is not "C<Proxy>") then the connect request +will automatically be changed to: + + $ENV{DBI_AUTOPROXY};dsn=$data_source + +C<DBI_AUTOPROXY> is typically set as "C<dbi:Proxy:hostname=...;port=...>". +If $ENV{DBI_AUTOPROXY} doesn't begin with 'C<dbi:>' then "dbi:Proxy:" +will be prepended to it first. See the DBD::Proxy documentation +for more details. + +If C<$username> or C<$password> are undefined (rather than just empty), +then the DBI will substitute the values of the C<DBI_USER> and C<DBI_PASS> +environment variables, respectively. The DBI will warn if the +environment variables are not defined. However, the everyday use +of these environment variables is not recommended for security +reasons. The mechanism is primarily intended to simplify testing. +See below for alternative way to specify the username and password. + +C<DBI-E<gt>connect> automatically installs the driver if it has not been +installed yet. Driver installation either returns a valid driver +handle, or it I<dies> with an error message that includes the string +"C<install_driver>" and the underlying problem. So C<DBI-E<gt>connect> +will die +on a driver installation failure and will only return C<undef> on a +connect failure, in which case C<$DBI::errstr> will hold the error message. +Use C<eval { ... }> if you need to catch the "C<install_driver>" error. + +The C<$data_source> argument (with the "C<dbi:...:>" prefix removed) and the +C<$username> and C<$password> arguments are then passed to the driver for +processing. The DBI does not define any interpretation for the +contents of these fields. The driver is free to interpret the +C<$data_source>, C<$username>, and C<$password> fields in any way, and supply +whatever defaults are appropriate for the engine being accessed. +(Oracle, for example, uses the ORACLE_SID and TWO_TASK environment +variables if no C<$data_source> is specified.) + +The C<AutoCommit> and C<PrintError> attributes for each connection +default to "on". (See L</AutoCommit> and L</PrintError> for more information.) +However, it is strongly recommended that you explicitly define C<AutoCommit> +rather than rely on the default. The C<PrintWarn> attribute defaults to +on if $^W is true, i.e., perl is running with warnings enabled. + +The C<\%attr> parameter can be used to alter the default settings of +C<PrintError>, C<RaiseError>, C<AutoCommit>, and other attributes. For example: + + $dbh = DBI->connect($data_source, $user, $pass, { + PrintError => 0, + AutoCommit => 0 + }); + +The username and password can also be specified using the attributes +C<Username> and C<Password>, in which case they take precedence +over the C<$username> and C<$password> parameters. + +You can also define connection attribute values within the C<$data_source> +parameter. For example: + + dbi:DriverName(PrintWarn=>1,PrintError=>0,Taint=>1):... + +Individual attributes values specified in this way take precedence over +any conflicting values specified via the C<\%attr> parameter to C<connect>. + +The C<dbi_connect_method> attribute can be used to specify which driver +method should be called to establish the connection. The only useful +values are 'connect', 'connect_cached', or some specialized case like +'Apache::DBI::connect' (which is automatically the default when running +within Apache). + +Where possible, each session (C<$dbh>) is independent from the transactions +in other sessions. This is useful when you need to hold cursors open +across transactions--for example, if you use one session for your long lifespan +cursors (typically read-only) and another for your short update +transactions. + +For compatibility with old DBI scripts, the driver can be specified by +passing its name as the fourth argument to C<connect> (instead of C<\%attr>): + + $dbh = DBI->connect($data_source, $user, $pass, $driver); + +In this "old-style" form of C<connect>, the C<$data_source> should not start +with "C<dbi:driver_name:>". (If it does, the embedded driver_name +will be ignored). Also note that in this older form of C<connect>, +the C<$dbh-E<gt>{AutoCommit}> attribute is I<undefined>, the +C<$dbh-E<gt>{PrintError}> attribute is off, and the old C<DBI_DBNAME> +environment variable is +checked if C<DBI_DSN> is not defined. Beware that this "old-style" +C<connect> will soon be withdrawn in a future version of DBI. + +=head3 C<connect_cached> + + $dbh = DBI->connect_cached($data_source, $username, $password) + or die $DBI::errstr; + $dbh = DBI->connect_cached($data_source, $username, $password, \%attr) + or die $DBI::errstr; + +C<connect_cached> is like L</connect>, except that the database handle +returned is also +stored in a hash associated with the given parameters. If another call +is made to C<connect_cached> with the same parameter values, then the +corresponding cached C<$dbh> will be returned if it is still valid. +The cached database handle is replaced with a new connection if it +has been disconnected or if the C<ping> method fails. + +Note that the behaviour of this method differs in several respects from the +behaviour of persistent connections implemented by Apache::DBI. +However, if Apache::DBI is loaded then C<connect_cached> will use it. + +Caching connections can be useful in some applications, but it can +also cause problems, such as too many connections, and so should +be used with care. In particular, avoid changing the attributes of +a database handle created via connect_cached() because it will affect +other code that may be using the same handle. When connect_cached() +returns a handle the attributes will be reset to their initial values. +This can cause problems, especially with the C<AutoCommit> attribute. + +Where multiple separate parts of a program are using connect_cached() +to connect to the same database with the same (initial) attributes +it is a good idea to add a private attribute to the connect_cached() +call to effectively limit the scope of the caching. For example: + + DBI->connect_cached(..., { private_foo_cachekey => "Bar", ... }); + +Handles returned from that connect_cached() call will only be returned +by other connect_cached() call elsewhere in the code if those other +calls also pass in the same attribute values, including the private one. +(I've used C<private_foo_cachekey> here as an example, you can use +any attribute name with a C<private_> prefix.) + +Taking that one step further, you can limit a particular connect_cached() +call to return handles unique to that one place in the code by setting the +private attribute to a unique value for that place: + + DBI->connect_cached(..., { private_foo_cachekey => __FILE__.__LINE__, ... }); + +By using a private attribute you still get connection caching for +the individual calls to connect_cached() but, by making separate +database connections for separate parts of the code, the database +handles are isolated from any attribute changes made to other handles. + +The cache can be accessed (and cleared) via the L</CachedKids> attribute: + + my $CachedKids_hashref = $dbh->{Driver}->{CachedKids}; + %$CachedKids_hashref = () if $CachedKids_hashref; + + +=head3 C<available_drivers> + + @ary = DBI->available_drivers; + @ary = DBI->available_drivers($quiet); + +Returns a list of all available drivers by searching for C<DBD::*> modules +through the directories in C<@INC>. By default, a warning is given if +some drivers are hidden by others of the same name in earlier +directories. Passing a true value for C<$quiet> will inhibit the warning. + +=head3 C<installed_drivers> + + %drivers = DBI->installed_drivers(); + +Returns a list of driver name and driver handle pairs for all drivers +'installed' (loaded) into the current process. The driver name does not +include the 'DBD::' prefix. + +To get a list of all drivers available in your perl installation you can use +L</available_drivers>. + +Added in DBI 1.49. + +=head3 C<installed_versions> + + DBI->installed_versions; + @ary = DBI->installed_versions; + %hash = DBI->installed_versions; + +Calls available_drivers() and attempts to load each of them in turn +using install_driver(). For each load that succeeds the driver +name and version number are added to a hash. When running under +L<DBI::PurePerl> drivers which appear not be pure-perl are ignored. + +When called in array context the list of successfully loaded drivers +is returned (without the 'DBD::' prefix). + +When called in scalar context a reference to the hash is returned +and the hash will also contain other entries for the C<DBI> version, +C<OS> name, etc. + +When called in a void context the installed_versions() method will +print out a formatted list of the hash contents, one per line. + +Due to the potentially high memory cost and unknown risks of loading +in an unknown number of drivers that just happen to be installed +on the system, this method is not recommended for general use. +Use available_drivers() instead. + +The installed_versions() method is primarily intended as a quick +way to see from the command line what's installed. For example: + + perl -MDBI -e 'DBI->installed_versions' + +The installed_versions() method was added in DBI 1.38. + +=head3 C<data_sources> + + @ary = DBI->data_sources($driver); + @ary = DBI->data_sources($driver, \%attr); + +Returns a list of data sources (databases) available via the named +driver. If C<$driver> is empty or C<undef>, then the value of the +C<DBI_DRIVER> environment variable is used. + +The driver will be loaded if it hasn't been already. Note that if the +driver loading fails then data_sources() I<dies> with an error message +that includes the string "C<install_driver>" and the underlying problem. + +Data sources are returned in a form suitable for passing to the +L</connect> method (that is, they will include the "C<dbi:$driver:>" prefix). + +Note that many drivers have no way of knowing what data sources might +be available for it. These drivers return an empty or incomplete list +or may require driver-specific attributes. + +There is also a data_sources() method defined for database handles. + + +=head3 C<trace> + + DBI->trace($trace_setting) + DBI->trace($trace_setting, $trace_filename) + DBI->trace($trace_setting, $trace_filehandle) + $trace_setting = DBI->trace; + +The C<DBI-E<gt>trace> method sets the I<global default> trace +settings and returns the I<previous> trace settings. It can also +be used to change where the trace output is sent. + +There's a similar method, C<$h-E<gt>trace>, which sets the trace +settings for the specific handle it's called on. + +See the L</TRACING> section for full details about the DBI's powerful +tracing facilities. + + +=head3 C<visit_handles> + + DBI->visit_handles( $coderef ); + DBI->visit_handles( $coderef, $info ); + +Where $coderef is a reference to a subroutine and $info is an arbitrary value +which, if undefined, defaults to a reference to an empty hash. Returns $info. + +For each installed driver handle, if any, $coderef is invoked as: + + $coderef->($driver_handle, $info); + +If the execution of $coderef returns a true value then L</visit_child_handles> +is called on that child handle and passed the returned value as $info. + +For example: + + my $info = $dbh->{Driver}->visit_child_handles(sub { + my ($h, $info) = @_; + ++$info->{ $h->{Type} }; # count types of handles (dr/db/st) + return $info; # visit kids + }); + +See also L</visit_child_handles>. + +=head2 DBI Utility Functions + +In addition to the DBI methods listed in the previous section, +the DBI package also provides several utility functions. + +These can be imported into your code by listing them in +the C<use> statement. For example: + + use DBI qw(neat data_diff); + +Alternatively, all these utility functions (except hash) can be +imported using the C<:utils> import tag. For example: + + use DBI qw(:utils); + +=head3 C<data_string_desc> + + $description = data_string_desc($string); + +Returns an informal description of the string. For example: + + UTF8 off, ASCII, 42 characters 42 bytes + UTF8 off, non-ASCII, 42 characters 42 bytes + UTF8 on, non-ASCII, 4 characters 6 bytes + UTF8 on but INVALID encoding, non-ASCII, 4 characters 6 bytes + UTF8 off, undef + +The initial C<UTF8> on/off refers to Perl's internal SvUTF8 flag. +If $string has the SvUTF8 flag set but the sequence of bytes it +contains are not a valid UTF-8 encoding then data_string_desc() +will report C<UTF8 on but INVALID encoding>. + +The C<ASCII> vs C<non-ASCII> portion shows C<ASCII> if I<all> the +characters in the string are ASCII (have code points <= 127). + +The data_string_desc() function was added in DBI 1.46. + +=head3 C<data_string_diff> + + $diff = data_string_diff($a, $b); + +Returns an informal description of the first character difference +between the strings. If both $a and $b contain the same sequence +of characters then data_string_diff() returns an empty string. +For example: + + Params a & b Result + ------------ ------ + 'aaa', 'aaa' '' + 'aaa', 'abc' 'Strings differ at index 2: a[2]=a, b[2]=b' + 'aaa', undef 'String b is undef, string a has 3 characters' + 'aaa', 'aa' 'String b truncated after 2 characters' + +Unicode characters are reported in C<\x{XXXX}> format. Unicode +code points in the range U+0800 to U+08FF are unassigned and most +likely to occur due to double-encoding. Characters in this range +are reported as C<\x{08XX}='C'> where C<C> is the corresponding +latin-1 character. + +The data_string_diff() function only considers logical I<characters> +and not the underlying encoding. See L</data_diff> for an alternative. + +The data_string_diff() function was added in DBI 1.46. + +=head3 C<data_diff> + + $diff = data_diff($a, $b); + $diff = data_diff($a, $b, $logical); + +Returns an informal description of the difference between two strings. +It calls L</data_string_desc> and L</data_string_diff> +and returns the combined results as a multi-line string. + +For example, C<data_diff("abc", "ab\x{263a}")> will return: + + a: UTF8 off, ASCII, 3 characters 3 bytes + b: UTF8 on, non-ASCII, 3 characters 5 bytes + Strings differ at index 2: a[2]=c, b[2]=\x{263A} + +If $a and $b are identical in both the characters they contain I<and> +their physical encoding then data_diff() returns an empty string. +If $logical is true then physical encoding differences are ignored +(but are still reported if there is a difference in the characters). + +The data_diff() function was added in DBI 1.46. + +=head3 C<neat> + + $str = neat($value); + $str = neat($value, $maxlen); + +Return a string containing a neat (and tidy) representation of the +supplied value. + +Strings will be quoted, although internal quotes will I<not> be escaped. +Values known to be numeric will be unquoted. Undefined (NULL) values +will be shown as C<undef> (without quotes). + +If the string is flagged internally as utf8 then double quotes will +be used, otherwise single quotes are used and unprintable characters +will be replaced by dot (.). + +For result strings longer than C<$maxlen> the result string will be +truncated to C<$maxlen-4> and "C<...'>" will be appended. If C<$maxlen> is 0 +or C<undef>, it defaults to C<$DBI::neat_maxlen> which, in turn, defaults to 400. + +This function is designed to format values for human consumption. +It is used internally by the DBI for L</trace> output. It should +typically I<not> be used for formatting values for database use. +(See also L</quote>.) + +=head3 C<neat_list> + + $str = neat_list(\@listref, $maxlen, $field_sep); + +Calls C<neat> on each element of the list and returns a string +containing the results joined with C<$field_sep>. C<$field_sep> defaults +to C<", ">. + +=head3 C<looks_like_number> + + @bool = looks_like_number(@array); + +Returns true for each element that looks like a number. +Returns false for each element that does not look like a number. +Returns C<undef> for each element that is undefined or empty. + +=head3 C<hash> + + $hash_value = DBI::hash($buffer, $type); + +Return a 32-bit integer 'hash' value corresponding to the contents of $buffer. +The $type parameter selects which kind of hash algorithm should be used. + +For the technically curious, type 0 (which is the default if $type +isn't specified) is based on the Perl 5.1 hash except that the value +is forced to be negative (for obscure historical reasons). +Type 1 is the better "Fowler / Noll / Vo" (FNV) hash. See +L<http://www.isthe.com/chongo/tech/comp/fnv/> for more information. +Both types are implemented in C and are very fast. + +This function doesn't have much to do with databases, except that +it can be handy to store hash values in a database. + +=head3 C<sql_type_cast> + + $sts = DBI::sql_type_cast($sv, $sql_type, $flags); + +sql_type_cast attempts to cast C<$sv> to the SQL type (see L<DBI +Constants>) specified in C<$sql_type>. At present only the SQL types +C<SQL_INTEGER>, C<SQL_DOUBLE> and C<SQL_NUMERIC> are supported. + +For C<SQL_INTEGER> the effect is similar to using the value in an expression +that requires an integer. It gives the perl scalar an 'integer aspect'. +(Technically the value gains an IV, or possibly a UV or NV if the value is too +large for an IV.) + +For C<SQL_DOUBLE> the effect is similar to using the value in an expression +that requires a general numeric value. It gives the perl scalar a 'numeric +aspect'. (Technically the value gains an NV.) + +C<SQL_NUMERIC> is similar to C<SQL_INTEGER> or C<SQL_DOUBLE> but more +general and more cautious. It will look at the string first and if it +looks like an integer (that will fit in an IV or UV) it will act like +C<SQL_INTEGER>, if it looks like a floating point value it will act +like C<SQL_DOUBLE>, if it looks like neither then it will do nothing - +and thereby avoid the warnings that would be generated by +C<SQL_INTEGER> and C<SQL_DOUBLE> when given non-numeric data. + +C<$flags> may be: + +=over 4 + +=item C<DBIstcf_DISCARD_STRING> + +If this flag is specified then when the driver successfully casts the +bound perl scalar to a non-string type then the string portion of the +scalar will be discarded. + +=item C<DBIstcf_STRICT> + +If C<$sv> cannot be cast to the requested C<$sql_type> then by default +it is left untouched and no error is generated. If you specify +C<DBIstcf_STRICT> and the cast fails, this will generate an error. + +=back + +The returned C<$sts> value is: + + -2 sql_type is not handled + -1 sv is undef so unchanged + 0 sv could not be cast cleanly and DBIstcf_STRICT was used + 1 sv could not be cast and DBIstcf_STRICT was not used + 2 sv was cast successfully + +This method is exported by the :utils tag and was introduced in DBI +1.611. + +=head2 DBI Dynamic Attributes + +Dynamic attributes are always associated with the I<last handle used> +(that handle is represented by C<$h> in the descriptions below). + +Where an attribute is equivalent to a method call, then refer to +the method call for all related documentation. + +Warning: these attributes are provided as a convenience but they +do have limitations. Specifically, they have a short lifespan: +because they are associated with +the last handle used, they should only be used I<immediately> after +calling the method that "sets" them. +If in any doubt, use the corresponding method call. + +=head3 C<$DBI::err> + +Equivalent to C<$h-E<gt>err>. + +=head3 C<$DBI::errstr> + +Equivalent to C<$h-E<gt>errstr>. + +=head3 C<$DBI::state> + +Equivalent to C<$h-E<gt>state>. + +=head3 C<$DBI::rows> + +Equivalent to C<$h-E<gt>rows>. Please refer to the documentation +for the L</rows> method. + +=head3 C<$DBI::lasth> + +Returns the DBI object handle used for the most recent DBI method call. +If the last DBI method call was a DESTROY then $DBI::lasth will return +the handle of the parent of the destroyed handle, if there is one. + + +=head1 METHODS COMMON TO ALL HANDLES + +The following methods can be used by all types of DBI handles. + +=head3 C<err> + + $rv = $h->err; + +Returns the I<native> database engine error code from the last driver +method called. The code is typically an integer but you should not +assume that. + +The DBI resets $h->err to undef before almost all DBI method calls, so the +value only has a short lifespan. Also, for most drivers, the statement +handles share the same error variable as the parent database handle, +so calling a method on one handle may reset the error on the +related handles. + +(Methods which don't reset err before being called include err() and errstr(), +obviously, state(), rows(), func(), trace(), trace_msg(), ping(), and the +tied hash attribute FETCH() and STORE() methods.) + +If you need to test for specific error conditions I<and> have your program be +portable to different database engines, then you'll need to determine what the +corresponding error codes are for all those engines and test for all of them. + +The DBI uses the value of $DBI::stderr as the C<err> value for internal errors. +Drivers should also do likewise. The default value for $DBI::stderr is 2000000000. + +A driver may return C<0> from err() to indicate a warning condition +after a method call. Similarly, a driver may return an empty string +to indicate a 'success with information' condition. In both these +cases the value is false but not undef. The errstr() and state() +methods may be used to retrieve extra information in these cases. + +See L</set_err> for more information. + +=head3 C<errstr> + + $str = $h->errstr; + +Returns the native database engine error message from the last DBI +method called. This has the same lifespan issues as the L</err> method +described above. + +The returned string may contain multiple messages separated by +newline characters. + +The errstr() method should not be used to test for errors, use err() +for that, because drivers may return 'success with information' or +warning messages via errstr() for methods that have not 'failed'. + +See L</set_err> for more information. + +=head3 C<state> + + $str = $h->state; + +Returns a state code in the standard SQLSTATE five character format. +Note that the specific success code C<00000> is translated to any empty string +(false). If the driver does not support SQLSTATE (and most don't), +then state() will return C<S1000> (General Error) for all errors. + +The driver is free to return any value via C<state>, e.g., warning +codes, even if it has not declared an error by returning a true value +via the L</err> method described above. + +The state() method should not be used to test for errors, use err() +for that, because drivers may return a 'success with information' or +warning state code via state() for methods that have not 'failed'. + +=head3 C<set_err> + + $rv = $h->set_err($err, $errstr); + $rv = $h->set_err($err, $errstr, $state); + $rv = $h->set_err($err, $errstr, $state, $method); + $rv = $h->set_err($err, $errstr, $state, $method, $rv); + +Set the C<err>, C<errstr>, and C<state> values for the handle. +This method is typically only used by DBI drivers and DBI subclasses. + +If the L</HandleSetErr> attribute holds a reference to a subroutine +it is called first. The subroutine can alter the $err, $errstr, $state, +and $method values. See L</HandleSetErr> for full details. +If the subroutine returns a true value then the handle C<err>, +C<errstr>, and C<state> values are not altered and set_err() returns +an empty list (it normally returns $rv which defaults to undef, see below). + +Setting C<err> to a I<true> value indicates an error and will trigger +the normal DBI error handling mechanisms, such as C<RaiseError> and +C<HandleError>, if they are enabled, when execution returns from +the DBI back to the application. + +Setting C<err> to C<""> indicates an 'information' state, and setting +it to C<"0"> indicates a 'warning' state. Setting C<err> to C<undef> +also sets C<errstr> to undef, and C<state> to C<"">, irrespective +of the values of the $errstr and $state parameters. + +The $method parameter provides an alternate method name for the +C<RaiseError>/C<PrintError>/C<PrintWarn> error string instead of +the fairly unhelpful 'C<set_err>'. + +The C<set_err> method normally returns undef. The $rv parameter +provides an alternate return value. + +Some special rules apply if the C<err> or C<errstr> +values for the handle are I<already> set... + +If C<errstr> is true then: "C< [err was %s now %s]>" is appended if $err is +true and C<err> is already true and the new err value differs from the original +one. Similarly "C< [state was %s now %s]>" is appended if $state is true and C<state> is +already true and the new state value differs from the original one. Finally +"C<\n>" and the new $errstr are appended if $errstr differs from the existing +errstr value. Obviously the C<%s>'s above are replaced by the corresponding values. + +The handle C<err> value is set to $err if: $err is true; or handle +C<err> value is undef; or $err is defined and the length is greater +than the handle C<err> length. The effect is that an 'information' +state only overrides undef; a 'warning' overrides undef or 'information', +and an 'error' state overrides anything. + +The handle C<state> value is set to $state if $state is true and +the handle C<err> value was set (by the rules above). + +Support for warning and information states was added in DBI 1.41. + +=head3 C<trace> + + $h->trace($trace_settings); + $h->trace($trace_settings, $trace_filename); + $trace_settings = $h->trace; + +The trace() method is used to alter the trace settings for a handle +(and any future children of that handle). It can also be used to +change where the trace output is sent. + +There's a similar method, C<DBI-E<gt>trace>, which sets the global +default trace settings. + +See the L</TRACING> section for full details about the DBI's powerful +tracing facilities. + +=head3 C<trace_msg> + + $h->trace_msg($message_text); + $h->trace_msg($message_text, $min_level); + +Writes C<$message_text> to the trace file if the trace level is +greater than or equal to $min_level (which defaults to 1). +Can also be called as C<DBI-E<gt>trace_msg($msg)>. + +See L</TRACING> for more details. + +=head3 C<func> + + $h->func(@func_arguments, $func_name) or die ...; + +The C<func> method can be used to call private non-standard and +non-portable methods implemented by the driver. Note that the function +name is given as the I<last> argument. + +It's also important to note that the func() method does not clear +a previous error ($DBI::err etc.) and it does not trigger automatic +error detection (RaiseError etc.) so you must check the return +status and/or $h->err to detect errors. + +(This method is not directly related to calling stored procedures. +Calling stored procedures is currently not defined by the DBI. +Some drivers, such as DBD::Oracle, support it in non-portable ways. +See driver documentation for more details.) + +See also install_method() in L<DBI::DBD> for how you can avoid needing to +use func() and gain direct access to driver-private methods. + +=head3 C<can> + + $is_implemented = $h->can($method_name); + +Returns true if $method_name is implemented by the driver or a +default method is provided by the DBI. +It returns false where a driver hasn't implemented a method and the +default method is provided by the DBI is just an empty stub. + +=head3 C<parse_trace_flags> + + $trace_settings_integer = $h->parse_trace_flags($trace_settings); + +Parses a string containing trace settings and returns the corresponding +integer value used internally by the DBI and drivers. + +The $trace_settings argument is a string containing a trace level +between 0 and 15 and/or trace flag names separated by vertical bar +("C<|>") or comma ("C<,>") characters. For example: C<"SQL|3|foo">. + +It uses the parse_trace_flag() method, described below, to process +the individual trace flag names. + +The parse_trace_flags() method was added in DBI 1.42. + +=head3 C<parse_trace_flag> + + $bit_flag = $h->parse_trace_flag($trace_flag_name); + +Returns the bit flag corresponding to the trace flag name in +$trace_flag_name. Drivers are expected to override this method and +check if $trace_flag_name is a driver specific trace flags and, if +not, then call the DBI's default parse_trace_flag(). + +The parse_trace_flag() method was added in DBI 1.42. + +=head3 C<private_attribute_info> + + $hash_ref = $h->private_attribute_info(); + +Returns a reference to a hash whose keys are the names of driver-private +handle attributes available for the kind of handle (driver, database, statement) +that the method was called on. + +For example, the return value when called with a DBD::Sybase $dbh could look like this: + + { + syb_dynamic_supported => undef, + syb_oc_version => undef, + syb_server_version => undef, + syb_server_version_string => undef, + } + +and when called with a DBD::Sybase $sth they could look like this: + + { + syb_types => undef, + syb_proc_status => undef, + syb_result_type => undef, + } + +The values should be undef. Meanings may be assigned to particular values in future. + +=head3 C<swap_inner_handle> + + $rc = $h1->swap_inner_handle( $h2 ); + $rc = $h1->swap_inner_handle( $h2, $allow_reparent ); + +Brain transplants for handles. You don't need to know about this +unless you want to become a handle surgeon. + +A DBI handle is a reference to a tied hash. A tied hash has an +I<inner> hash that actually holds the contents. The swap_inner_handle() +method swaps the inner hashes between two handles. The $h1 and $h2 +handles still point to the same tied hashes, but what those hashes +are tied to has been swapped. In effect $h1 I<becomes> $h2 and +vice-versa. This is powerful stuff, expect problems. Use with care. + +As a small safety measure, the two handles, $h1 and $h2, have to +share the same parent unless $allow_reparent is true. + +The swap_inner_handle() method was added in DBI 1.44. + +Here's a quick kind of 'diagram' as a worked example to help think about what's +happening: + + Original state: + dbh1o -> dbh1i + sthAo -> sthAi(dbh1i) + dbh2o -> dbh2i + + swap_inner_handle dbh1o with dbh2o: + dbh2o -> dbh1i + sthAo -> sthAi(dbh1i) + dbh1o -> dbh2i + + create new sth from dbh1o: + dbh2o -> dbh1i + sthAo -> sthAi(dbh1i) + dbh1o -> dbh2i + sthBo -> sthBi(dbh2i) + + swap_inner_handle sthAo with sthBo: + dbh2o -> dbh1i + sthBo -> sthAi(dbh1i) + dbh1o -> dbh2i + sthAo -> sthBi(dbh2i) + +=head3 C<visit_child_handles> + + $h->visit_child_handles( $coderef ); + $h->visit_child_handles( $coderef, $info ); + +Where $coderef is a reference to a subroutine and $info is an arbitrary value +which, if undefined, defaults to a reference to an empty hash. Returns $info. + +For each child handle of $h, if any, $coderef is invoked as: + + $coderef->($child_handle, $info); + +If the execution of $coderef returns a true value then C<visit_child_handles> +is called on that child handle and passed the returned value as $info. + +For example: + + # count database connections with names (DSN) matching a pattern + my $connections = 0; + $dbh->{Driver}->visit_child_handles(sub { + my ($h, $info) = @_; + ++$connections if $h->{Name} =~ /foo/; + return 0; # don't visit kids + }) + +See also L</visit_handles>. + +=head1 ATTRIBUTES COMMON TO ALL HANDLES + +These attributes are common to all types of DBI handles. + +Some attributes are inherited by child handles. That is, the value +of an inherited attribute in a newly created statement handle is the +same as the value in the parent database handle. Changes to attributes +in the new statement handle do not affect the parent database handle +and changes to the database handle do not affect existing statement +handles, only future ones. + +Attempting to set or get the value of an unknown attribute generates a warning, +except for private driver specific attributes (which all have names +starting with a lowercase letter). + +Example: + + $h->{AttributeName} = ...; # set/write + ... = $h->{AttributeName}; # get/read + +=head3 C<Warn> + +Type: boolean, inherited + +The C<Warn> attribute enables useful warnings for certain bad +practices. It is enabled by default and should only be disabled in +rare circumstances. Since warnings are generated using the Perl +C<warn> function, they can be intercepted using the Perl C<$SIG{__WARN__}> +hook. + +The C<Warn> attribute is not related to the C<PrintWarn> attribute. + +=head3 C<Active> + +Type: boolean, read-only + +The C<Active> attribute is true if the handle object is "active". This is rarely used in +applications. The exact meaning of active is somewhat vague at the +moment. For a database handle it typically means that the handle is +connected to a database (C<$dbh-E<gt>disconnect> sets C<Active> off). For +a statement handle it typically means that the handle is a C<SELECT> +that may have more data to fetch. (Fetching all the data or calling C<$sth-E<gt>finish> +sets C<Active> off.) + +=head3 C<Executed> + +Type: boolean + +The C<Executed> attribute is true if the handle object has been "executed". +Currently only the $dbh do() method and the $sth execute(), execute_array(), +and execute_for_fetch() methods set the C<Executed> attribute. + +When it's set on a handle it is also set on the parent handle at the +same time. So calling execute() on a $sth also sets the C<Executed> +attribute on the parent $dbh. + +The C<Executed> attribute for a database handle is cleared by the commit() and +rollback() methods (even if they fail). The C<Executed> attribute of a +statement handle is not cleared by the DBI under any circumstances and so acts +as a permanent record of whether the statement handle was ever used. + +The C<Executed> attribute was added in DBI 1.41. + +=head3 C<Kids> + +Type: integer, read-only + +For a driver handle, C<Kids> is the number of currently existing database +handles that were created from that driver handle. For a database +handle, C<Kids> is the number of currently existing statement handles that +were created from that database handle. +For a statement handle, the value is zero. + +=head3 C<ActiveKids> + +Type: integer, read-only + +Like C<Kids>, but only counting those that are C<Active> (as above). + +=head3 C<CachedKids> + +Type: hash ref + +For a database handle, C<CachedKids> returns a reference to the cache (hash) of +statement handles created by the L</prepare_cached> method. For a +driver handle, returns a reference to the cache (hash) of +database handles created by the L</connect_cached> method. + +=head3 C<Type> + +Type: scalar, read-only + +The C<Type> attribute identifies the type of a DBI handle. Returns +"dr" for driver handles, "db" for database handles and "st" for +statement handles. + +=head3 C<ChildHandles> + +Type: array ref + +The ChildHandles attribute contains a reference to an array of all the +handles created by this handle which are still accessible. The +contents of the array are weak-refs and will become undef when the +handle goes out of scope. + +C<ChildHandles> returns undef if your perl version does not support weak +references (check the L<Scalar::Util|Scalar::Util> module). The referenced +array returned should be treated as read-only. + +For example, to enumerate all driver handles, database handles and +statement handles: + + sub show_child_handles { + my ($h, $level) = @_; + printf "%sh %s %s\n", $h->{Type}, "\t" x $level, $h; + show_child_handles($_, $level + 1) + for (grep { defined } @{$h->{ChildHandles}}); + } + + my %drivers = DBI->installed_drivers(); + show_child_handles($_, 0) for (values %drivers); + +=head3 C<CompatMode> + +Type: boolean, inherited + +The C<CompatMode> attribute is used by emulation layers (such as +Oraperl) to enable compatible behaviour in the underlying driver +(e.g., DBD::Oracle) for this handle. Not normally set by application code. + +It also has the effect of disabling the 'quick FETCH' of attribute +values from the handles attribute cache. So all attribute values +are handled by the drivers own FETCH method. This makes them slightly +slower but is useful for special-purpose drivers like DBD::Multiplex. + +=head3 C<InactiveDestroy> + +Type: boolean + +The default value, false, means a handle will be fully destroyed +as normal when the last reference to it is removed, just as you'd expect. + +If set true then the handle will be treated by the DESTROY as if it was no +longer Active, and so the I<database engine> related effects of DESTROYing a +handle will be skipped. Think of the name as meaning 'treat the handle as +not-Active in the DESTROY method'. + +For a database handle, this attribute does not disable an I<explicit> +call to the disconnect method, only the implicit call from DESTROY +that happens if the handle is still marked as C<Active>. + +This attribute is specifically designed for use in Unix applications +that "fork" child processes. For some drivers, when the child process exits +the destruction of inherited handles cause the corresponding handles in the +parent process to cease working. + +Either the parent or the child process, but not both, should set +C<InactiveDestroy> true on all their shared handles. Alternatively the +L</AutoInactiveDestroy> can be set in the parent on connect. + +To help tracing applications using fork the process id is shown in +the trace log whenever a DBI or handle trace() method is called. +The process id also shown for I<every> method call if the DBI trace +level (not handle trace level) is set high enough to show the trace +from the DBI's method dispatcher, e.g. >= 9. + +=head3 C<AutoInactiveDestroy> + +Type: boolean, inherited + +The L</InactiveDestroy> attribute, described above, needs to be explicitly set +in the child process after a fork(). This is a problem if the code that performs +the fork() is not under your control, perhaps in a third-party module. +Use C<AutoInactiveDestroy> to get around this situation. + +If set true, the DESTROY method will check the process id of the handle and, if +different from the current process id, it will set the I<InactiveDestroy> attribute. + +This is the example it's designed to deal with: + + my $dbh = DBI->connect(...); + some_code_that_forks(); # Perhaps without your knowledge + # Child process dies, destroying the inherited dbh + $dbh->do(...); # Breaks because parent $dbh is now broken + +The C<AutoInactiveDestroy> attribute was added in DBI 1.614. + +=head3 C<PrintWarn> + +Type: boolean, inherited + +The C<PrintWarn> attribute controls the printing of warnings recorded +by the driver. When set to a true value the DBI will check method +calls to see if a warning condition has been set. If so, the DBI +will effectively do a C<warn("$class $method warning: $DBI::errstr")> +where C<$class> is the driver class and C<$method> is the name of +the method which failed. E.g., + + DBD::Oracle::db execute warning: ... warning text here ... + +By default, C<DBI-E<gt>connect> sets C<PrintWarn> "on" if $^W is true, +i.e., perl is running with warnings enabled. + +If desired, the warnings can be caught and processed using a C<$SIG{__WARN__}> +handler or modules like CGI::Carp and CGI::ErrorWrap. + +See also L</set_err> for how warnings are recorded and L</HandleSetErr> +for how to influence it. + +Fetching the full details of warnings can require an extra round-trip +to the database server for some drivers. In which case the driver +may opt to only fetch the full details of warnings if the C<PrintWarn> +attribute is true. If C<PrintWarn> is false then these drivers should +still indicate the fact that there were warnings by setting the +warning string to, for example: "3 warnings". + +=head3 C<PrintError> + +Type: boolean, inherited + +The C<PrintError> attribute can be used to force errors to generate warnings (using +C<warn>) in addition to returning error codes in the normal way. When set +"on", any method which results in an error occurring will cause the DBI to +effectively do a C<warn("$class $method failed: $DBI::errstr")> where C<$class> +is the driver class and C<$method> is the name of the method which failed. E.g., + + DBD::Oracle::db prepare failed: ... error text here ... + +By default, C<DBI-E<gt>connect> sets C<PrintError> "on". + +If desired, the warnings can be caught and processed using a C<$SIG{__WARN__}> +handler or modules like CGI::Carp and CGI::ErrorWrap. + +=head3 C<RaiseError> + +Type: boolean, inherited + +The C<RaiseError> attribute can be used to force errors to raise exceptions rather +than simply return error codes in the normal way. It is "off" by default. +When set "on", any method which results in an error will cause +the DBI to effectively do a C<die("$class $method failed: $DBI::errstr")>, +where C<$class> is the driver class and C<$method> is the name of the method +that failed. E.g., + + DBD::Oracle::db prepare failed: ... error text here ... + +If you turn C<RaiseError> on then you'd normally turn C<PrintError> off. +If C<PrintError> is also on, then the C<PrintError> is done first (naturally). + +Typically C<RaiseError> is used in conjunction with C<eval { ... }> +to catch the exception that's been thrown and followed by an +C<if ($@) { ... }> block to handle the caught exception. +For example: + + eval { + ... + $sth->execute(); + ... + }; + if ($@) { + # $sth->err and $DBI::err will be true if error was from DBI + warn $@; # print the error + ... # do whatever you need to deal with the error + } + +In that eval block the $DBI::lasth variable can be useful for +diagnosis and reporting if you can't be sure which handle triggered +the error. For example, $DBI::lasth->{Type} and $DBI::lasth->{Statement}. + +See also L</Transactions>. + +If you want to temporarily turn C<RaiseError> off (inside a library function +that is likely to fail, for example), the recommended way is like this: + + { + local $h->{RaiseError}; # localize and turn off for this block + ... + } + +The original value will automatically and reliably be restored by Perl, +regardless of how the block is exited. +The same logic applies to other attributes, including C<PrintError>. + +=head3 C<HandleError> + +Type: code ref, inherited + +The C<HandleError> attribute can be used to provide your own alternative behaviour +in case of errors. If set to a reference to a subroutine then that +subroutine is called when an error is detected (at the same point that +C<RaiseError> and C<PrintError> are handled). + +The subroutine is called with three parameters: the error message +string that C<RaiseError> and C<PrintError> would use, +the DBI handle being used, and the first value being returned by +the method that failed (typically undef). + +If the subroutine returns a false value then the C<RaiseError> +and/or C<PrintError> attributes are checked and acted upon as normal. + +For example, to C<die> with a full stack trace for any error: + + use Carp; + $h->{HandleError} = sub { confess(shift) }; + +Or to turn errors into exceptions: + + use Exception; # or your own favourite exception module + $h->{HandleError} = sub { Exception->new('DBI')->raise($_[0]) }; + +It is possible to 'stack' multiple HandleError handlers by using +closures: + + sub your_subroutine { + my $previous_handler = $h->{HandleError}; + $h->{HandleError} = sub { + return 1 if $previous_handler and &$previous_handler(@_); + ... your code here ... + }; + } + +Using a C<my> inside a subroutine to store the previous C<HandleError> +value is important. See L<perlsub> and L<perlref> for more information +about I<closures>. + +It is possible for C<HandleError> to alter the error message that +will be used by C<RaiseError> and C<PrintError> if it returns false. +It can do that by altering the value of $_[0]. This example appends +a stack trace to all errors and, unlike the previous example using +Carp::confess, this will work C<PrintError> as well as C<RaiseError>: + + $h->{HandleError} = sub { $_[0]=Carp::longmess($_[0]); 0; }; + +It is also possible for C<HandleError> to hide an error, to a limited +degree, by using L</set_err> to reset $DBI::err and $DBI::errstr, +and altering the return value of the failed method. For example: + + $h->{HandleError} = sub { + return 0 unless $_[0] =~ /^\S+ fetchrow_arrayref failed:/; + return 0 unless $_[1]->err == 1234; # the error to 'hide' + $h->set_err(undef,undef); # turn off the error + $_[2] = [ ... ]; # supply alternative return value + return 1; + }; + +This only works for methods which return a single value and is hard +to make reliable (avoiding infinite loops, for example) and so isn't +recommended for general use! If you find a I<good> use for it then +please let me know. + +=head3 C<HandleSetErr> + +Type: code ref, inherited + +The C<HandleSetErr> attribute can be used to intercept +the setting of handle C<err>, C<errstr>, and C<state> values. +If set to a reference to a subroutine then that subroutine is called +whenever set_err() is called, typically by the driver or a subclass. + +The subroutine is called with five arguments, the first five that +were passed to set_err(): the handle, the C<err>, C<errstr>, and +C<state> values being set, and the method name. These can be altered +by changing the values in the @_ array. The return value affects +set_err() behaviour, see L</set_err> for details. + +It is possible to 'stack' multiple HandleSetErr handlers by using +closures. See L</HandleError> for an example. + +The C<HandleSetErr> and C<HandleError> subroutines differ in subtle +but significant ways. HandleError is only invoked at the point where +the DBI is about to return to the application with C<err> set true. +It's not invoked by the failure of a method that's been called by +another DBI method. HandleSetErr, on the other hand, is called +whenever set_err() is called with a defined C<err> value, even if false. +So it's not just for errors, despite the name, but also warn and info states. +The set_err() method, and thus HandleSetErr, may be called multiple +times within a method and is usually invoked from deep within driver code. + +In theory a driver can use the return value from HandleSetErr via +set_err() to decide whether to continue or not. If set_err() returns +an empty list, indicating that the HandleSetErr code has 'handled' +the 'error', the driver could then continue instead of failing (if +that's a reasonable thing to do). This isn't excepted to be +common and any such cases should be clearly marked in the driver +documentation and discussed on the dbi-dev mailing list. + +The C<HandleSetErr> attribute was added in DBI 1.41. + +=head3 C<ErrCount> + +Type: unsigned integer + +The C<ErrCount> attribute is incremented whenever the set_err() +method records an error. It isn't incremented by warnings or +information states. It is not reset by the DBI at any time. + +The C<ErrCount> attribute was added in DBI 1.41. Older drivers may +not have been updated to use set_err() to record errors and so this +attribute may not be incremented when using them. + + +=head3 C<ShowErrorStatement> + +Type: boolean, inherited + +The C<ShowErrorStatement> attribute can be used to cause the relevant +Statement text to be appended to the error messages generated by +the C<RaiseError>, C<PrintError>, and C<PrintWarn> attributes. +Only applies to errors on statement handles +plus the prepare(), do(), and the various C<select*()> database handle methods. +(The exact format of the appended text is subject to change.) + +If C<$h-E<gt>{ParamValues}> returns a hash reference of parameter +(placeholder) values then those are formatted and appended to the +end of the Statement text in the error message. + +=head3 C<TraceLevel> + +Type: integer, inherited + +The C<TraceLevel> attribute can be used as an alternative to the +L</trace> method to set the DBI trace level and trace flags for a +specific handle. See L</TRACING> for more details. + +The C<TraceLevel> attribute is especially useful combined with +C<local> to alter the trace settings for just a single block of code. + +=head3 C<FetchHashKeyName> + +Type: string, inherited + +The C<FetchHashKeyName> attribute is used to specify whether the fetchrow_hashref() +method should perform case conversion on the field names used for +the hash keys. For historical reasons it defaults to 'C<NAME>' but +it is recommended to set it to 'C<NAME_lc>' (convert to lower case) +or 'C<NAME_uc>' (convert to upper case) according to your preference. +It can only be set for driver and database handles. For statement +handles the value is frozen when prepare() is called. + + +=head3 C<ChopBlanks> + +Type: boolean, inherited + +The C<ChopBlanks> attribute can be used to control the trimming of trailing space +characters from fixed width character (CHAR) fields. No other field +types are affected, even where field values have trailing spaces. + +The default is false (although it is possible that the default may change). +Applications that need specific behaviour should set the attribute as +needed. + +Drivers are not required to support this attribute, but any driver which +does not support it must arrange to return C<undef> as the attribute value. + + +=head3 C<LongReadLen> + +Type: unsigned integer, inherited + +The C<LongReadLen> attribute may be used to control the maximum +length of 'long' type fields (LONG, BLOB, CLOB, MEMO, etc.) which the driver will +read from the database automatically when it fetches each row of data. + +The C<LongReadLen> attribute only relates to fetching and reading +long values; it is not involved in inserting or updating them. + +A value of 0 means not to automatically fetch any long data. +Drivers may return undef or an empty string for long fields when +C<LongReadLen> is 0. + +The default is typically 0 (zero) or 80 bytes but may vary between drivers. +Applications fetching long fields should set this value to slightly +larger than the longest long field value to be fetched. + +Some databases return some long types encoded as pairs of hex digits. +For these types, C<LongReadLen> relates to the underlying data +length and not the doubled-up length of the encoded string. + +Changing the value of C<LongReadLen> for a statement handle after it +has been C<prepare>'d will typically have no effect, so it's common to +set C<LongReadLen> on the C<$dbh> before calling C<prepare>. + +For most drivers the value used here has a direct effect on the +memory used by the statement handle while it's active, so don't be +too generous. If you can't be sure what value to use you could +execute an extra select statement to determine the longest value. +For example: + + $dbh->{LongReadLen} = $dbh->selectrow_array(qq{ + SELECT MAX(OCTET_LENGTH(long_column_name)) + FROM table WHERE ... + }); + $sth = $dbh->prepare(qq{ + SELECT long_column_name, ... FROM table WHERE ... + }); + +You may need to take extra care if the table can be modified between +the first select and the second being executed. You may also need to +use a different function if OCTET_LENGTH() does not work for long +types in your database. For example, for Sybase use DATALENGTH() and +for Oracle use LENGTHB(). + +See also L</LongTruncOk> for information on truncation of long types. + +=head3 C<LongTruncOk> + +Type: boolean, inherited + +The C<LongTruncOk> attribute may be used to control the effect of +fetching a long field value which has been truncated (typically +because it's longer than the value of the C<LongReadLen> attribute). + +By default, C<LongTruncOk> is false and so fetching a long value that +needs to be truncated will cause the fetch to fail. +(Applications should always be sure to +check for errors after a fetch loop in case an error, such as a divide +by zero or long field truncation, caused the fetch to terminate +prematurely.) + +If a fetch fails due to a long field truncation when C<LongTruncOk> is +false, many drivers will allow you to continue fetching further rows. + +See also L</LongReadLen>. + +=head3 C<TaintIn> + +Type: boolean, inherited + +If the C<TaintIn> attribute is set to a true value I<and> Perl is running in +taint mode (e.g., started with the C<-T> option), then all the arguments +to most DBI method calls are checked for being tainted. I<This may change.> + +The attribute defaults to off, even if Perl is in taint mode. +See L<perlsec> for more about taint mode. If Perl is not +running in taint mode, this attribute has no effect. + +When fetching data that you trust you can turn off the TaintIn attribute, +for that statement handle, for the duration of the fetch loop. + +The C<TaintIn> attribute was added in DBI 1.31. + +=head3 C<TaintOut> + +Type: boolean, inherited + +If the C<TaintOut> attribute is set to a true value I<and> Perl is running in +taint mode (e.g., started with the C<-T> option), then most data fetched +from the database is considered tainted. I<This may change.> + +The attribute defaults to off, even if Perl is in taint mode. +See L<perlsec> for more about taint mode. If Perl is not +running in taint mode, this attribute has no effect. + +When fetching data that you trust you can turn off the TaintOut attribute, +for that statement handle, for the duration of the fetch loop. + +Currently only fetched data is tainted. It is possible that the results +of other DBI method calls, and the value of fetched attributes, may +also be tainted in future versions. That change may well break your +applications unless you take great care now. If you use DBI Taint mode, +please report your experience and any suggestions for changes. + +The C<TaintOut> attribute was added in DBI 1.31. + +=head3 C<Taint> + +Type: boolean, inherited + +The C<Taint> attribute is a shortcut for L</TaintIn> and L</TaintOut> (it is also present +for backwards compatibility). + +Setting this attribute sets both L</TaintIn> and L</TaintOut>, and retrieving +it returns a true value if and only if L</TaintIn> and L</TaintOut> are +both set to true values. + +=head3 C<Profile> + +Type: inherited + +The C<Profile> attribute enables the collection and reporting of +method call timing statistics. See the L<DBI::Profile> module +documentation for I<much> more detail. + +The C<Profile> attribute was added in DBI 1.24. + +=head3 C<ReadOnly> + +Type: boolean, inherited + +An application can set the C<ReadOnly> attribute of a handle to a true value to +indicate that it will not be attempting to make any changes using that handle +or any children of it. + +Note that the exact definition of 'read only' is rather fuzzy. +For more details see the documentation for the driver you're using. + +If the driver can make the handle truly read-only then it should +(unless doing so would have unpleasant side effect, like changing the +consistency level from per-statement to per-session). +Otherwise the attribute is simply advisory. + +A driver can set the C<ReadOnly> attribute itself to indicate that the data it +is connected to cannot be changed for some reason. + +Library modules and proxy drivers can use the attribute to influence +their behavior. For example, the DBD::Gofer driver considers the +C<ReadOnly> attribute when making a decision about whether to retry an +operation that failed. + +The attribute should be set to 1 or 0 (or undef). Other values are reserved. + +=head3 C<Callbacks> + +Type: hash ref + +The DBI callback mechanism lets you intercept, and optionally replace, any +method call on a DBI handle. At the extreme, it lets you become a puppet +master, deceiving the application in any way you want. + +The C<Callbacks> attribute is a hash reference where the keys are DBI method +names and the values are code references. For each key naming a method, the +DBI will execute the associated code reference before executing the method. + +The arguments to the code reference will be the same as to the method, +including the invocant (a database handle or statement handle). For example, +say that to callback to some code on a call to C<prepare()>: + + $dbh->{Callbacks} = { + prepare => sub { + my ($dbh, $query, $attrs) = @_; + print "Preparing q{$query}\n" + }, + }; + +The callback would then be executed when you called the C<prepare()> method: + + $dbh->prepare('SELECT 1'); + +And the output of course would be: + + Preparing q{SELECT 1} + +Because callbacks are executed I<before> the methods +they're associated with, you can modify the arguments before they're passed on +to the method call. For example, to make sure that all calls to C<prepare()> +are immediately prepared by L<DBD::Pg>, add a callback that makes sure that +the C<pg_prepare_now> attribute is always set: + + my $dbh = DBI->connect($dsn, $username, $auth, { + Callbacks => { + prepare => sub { + $_[2] ||= {}; + $_[2]->{pg_prepare_now} = 1; + return; # must return nothing + }, + } + }); + +Note that we are editing the contents of C<@_> directly. In this case we've +created the attributes hash if it's not passed to the C<prepare> call. + +You can also prevent the associated method from ever executing. While a +callback executes, C<$_> holds the method name. (This allows multiple callbacks +to share the same code reference and still know what method was called.) +To prevent the method from +executing, simply C<undef $_>. For example, if you wanted to disable calls to +C<ping()>, you could do this: + + $dbh->{Callbacks} = { + ping => sub { + # tell dispatch to not call the method: + undef $_; + # return this value instead: + return "42 bells"; + } + }; + +As with other attributes, Callbacks can be specified on a handle or via the +attributes to C<connect()>. Callbacks can also be applied to a statement +methods on a statement handle. For example: + + $sth->{Callbacks} = { + execute => sub { + print "Executing ", shift->{Statement}, "\n"; + } + }; + +The C<Callbacks> attribute of a database handle isn't copied to any statement +handles it creates. So setting callbacks for a statement handle requires you to +set the C<Callbacks> attribute on the statement handle yourself, as in the +example above, or use the special C<ChildCallbacks> key described below. + +B<Special Keys in Callbacks Attribute> + +In addition to DBI handle method names, the C<Callbacks> hash reference +supports three additional keys. + +The first is the C<ChildCallbacks> key. When a statement handle is created from +a database handle the C<ChildCallbacks> key of the database handle's +C<Callbacks> attribute, if any, becomes the new C<Callbacks> attribute of the +statement handle. +This allows you to define callbacks for all statement handles created from a +database handle. For example, if you wanted to count how many times C<execute> +was called in your application, you could write: + + my $exec_count = 0; + my $dbh = DBI->connect( $dsn, $username, $auth, { + Callbacks => { + ChildCallbacks => { + execute => sub { $exec_count++; return; } + } + } + }); + + END { + print "The execute method was called $exec_count times\n"; + } + +The other two special keys are C<connect_cached.new> and +C<connect_cached.reused>. These keys define callbacks that are called when +C<connect_cached()> is called, but allow different behaviors depending on +whether a new handle is created or a handle is returned. The callback is +invoked with these arguments: C<$dbh, $dsn, $user, $auth, $attr>. + +For example, some applications uses C<connect_cached()> to connect with +C<AutoCommit> enabled and then disable C<AutoCommit> temporarily for +transactions. If C<connect_cached()> is called during a transaction, perhaps in +a utility method, then it might select the same cached handle and then force +C<AutoCommit> on, forcing a commit of the transaction. See the L</connect_cached> +documentation for one way to deal with that. Here we'll describe an alternative +approach using a callback. + +Because the C<connect_cached.*> callbacks are invoked before connect_cached() +has applied the connect attributes you can use a callback to edit the attributes +that will be applied. To prevent a cached handle from having its transactions +committed before it's returned, you can eliminate the C<AutoCommit> attribute +in a C<connect_cached.reused> callback, like so: + + my $cb = { + 'connect_cached.reused' => sub { delete $_[4]->{AutoCommit} }, + }; + + sub dbh { + my $self = shift; + DBI->connect_cached( $dsn, $username, $auth, { + PrintError => 0, + RaiseError => 1, + AutoCommit => 1, + Callbacks => $cb, + }); + } + +The upshot is that new database handles are created with C<AutoCommit> +enabled, while cached database handles are left in whatever transaction state +they happened to be in when retrieved from the cache. + +A more common application for callbacks is setting connection state only when a +new connection is made (by connect() or connect_cached()). Adding a callback to +the connected method makes this easy. +This method is a no-op by default (unless you subclass the DBI and change it). +The DBI calls it to indicate that a new connection has been made and the connection +attributes have all been set. You can +give it a bit of added functionality by applying a callback to it. For +example, to make sure that MySQL understands your application's ANSI-compliant +SQL, set it up like so: + + my $dbh = DBI->connect($dsn, $username, $auth, { + Callbacks => { + connected => sub { + shift->do(q{ + SET SESSION sql_mode='ansi,strict_trans_tables,no_auto_value_on_zero'; + }); + return; + }, + } + }); + +One significant limitation with callbacks is that there can only be one per +method per handle. This means it's easy for one use of callbacks to interfere +with, or typically simply overwrite, another use of callbacks. For this reason +modules using callbacks should document the fact clearly so application authors +can tell if use of callbacks by the module will clash with use of callbacks by +the application. + +You might be able to work around this issue by taking a copy of the original +callback and calling it within your own. For example: + + my $prev_cb = $h->{Callbacks}{method_name}; + $h->{Callbacks}{method_name} = sub { + if ($prev_cb) { + my @result = $prev_cb->(@_); + return @result if not $_; # $prev_cb vetoed call + } + ... your callback logic here ... + }; + +=head3 C<private_your_module_name_*> + +The DBI provides a way to store extra information in a DBI handle as +"private" attributes. The DBI will allow you to store and retrieve any +attribute which has a name starting with "C<private_>". + +It is I<strongly> recommended that you use just I<one> private +attribute (e.g., use a hash ref) I<and> give it a long and unambiguous +name that includes the module or application name that the attribute +relates to (e.g., "C<private_YourFullModuleName_thingy>"). + +Because of the way the Perl tie mechanism works you cannot reliably +use the C<||=> operator directly to initialise the attribute, like this: + + my $foo = $dbh->{private_yourmodname_foo} ||= { ... }; # WRONG + +you should use a two step approach like this: + + my $foo = $dbh->{private_yourmodname_foo}; + $foo ||= $dbh->{private_yourmodname_foo} = { ... }; + +This attribute is primarily of interest to people sub-classing DBI, +or for applications to piggy-back extra information onto DBI handles. + +=head1 DBI DATABASE HANDLE OBJECTS + +This section covers the methods and attributes associated with +database handles. + +=head2 Database Handle Methods + +The following methods are specified for DBI database handles: + +=head3 C<clone> + + $new_dbh = $dbh->clone(\%attr); + +The C<clone> method duplicates the $dbh connection by connecting +with the same parameters ($dsn, $user, $password) as originally used. + +The attributes for the cloned connect are the same as those used +for the I<original> connect, with any other attributes in C<\%attr> +merged over them. Effectively the same as doing: + + %attributes_used = ( %original_attributes, %attr ); + +If \%attr is not given then it defaults to a hash containing all +the attributes in the attribute cache of $dbh excluding any non-code +references, plus the main boolean attributes (RaiseError, PrintError, +AutoCommit, etc.). I<This behaviour is unreliable and so use of clone without +an argument is deprecated and may cause a warning in a future release.> + +The clone method can be used even if the database handle is disconnected. + +The C<clone> method was added in DBI 1.33. + +=head3 C<data_sources> + + @ary = $dbh->data_sources(); + @ary = $dbh->data_sources(\%attr); + +Returns a list of data sources (databases) available via the $dbh +driver's data_sources() method, plus any extra data sources that +the driver can discover via the connected $dbh. Typically the extra +data sources are other databases managed by the same server process +that the $dbh is connected to. + +Data sources are returned in a form suitable for passing to the +L</connect> method (that is, they will include the "C<dbi:$driver:>" prefix). + +The data_sources() method, for a $dbh, was added in DBI 1.38. + +=head3 C<do> + + $rows = $dbh->do($statement) or die $dbh->errstr; + $rows = $dbh->do($statement, \%attr) or die $dbh->errstr; + $rows = $dbh->do($statement, \%attr, @bind_values) or die ... + +Prepare and execute a single statement. Returns the number of rows +affected or C<undef> on error. A return value of C<-1> means the +number of rows is not known, not applicable, or not available. + +This method is typically most useful for I<non>-C<SELECT> statements that +either cannot be prepared in advance (due to a limitation of the +driver) or do not need to be executed repeatedly. It should not +be used for C<SELECT> statements because it does not return a statement +handle (so you can't fetch any data). + +The default C<do> method is logically similar to: + + sub do { + my($dbh, $statement, $attr, @bind_values) = @_; + my $sth = $dbh->prepare($statement, $attr) or return undef; + $sth->execute(@bind_values) or return undef; + my $rows = $sth->rows; + ($rows == 0) ? "0E0" : $rows; # always return true if no error + } + +For example: + + my $rows_deleted = $dbh->do(q{ + DELETE FROM table + WHERE status = ? + }, undef, 'DONE') or die $dbh->errstr; + +Using placeholders and C<@bind_values> with the C<do> method can be +useful because it avoids the need to correctly quote any variables +in the C<$statement>. But if you'll be executing the statement many +times then it's more efficient to C<prepare> it once and call +C<execute> many times instead. + +The C<q{...}> style quoting used in this example avoids clashing with +quotes that may be used in the SQL statement. Use the double-quote-like +C<qq{...}> operator if you want to interpolate variables into the string. +See L<perlop/"Quote and Quote-like Operators"> for more details. + +Note drivers are free to avoid the overhead of creating an DBI +statement handle for do(), especially if there are no parameters. In +this case error handlers, if invoked during do(), will be passed the +database handle. + +=head3 C<last_insert_id> + + $rv = $dbh->last_insert_id($catalog, $schema, $table, $field); + $rv = $dbh->last_insert_id($catalog, $schema, $table, $field, \%attr); + +Returns a value 'identifying' the row just inserted, if possible. +Typically this would be a value assigned by the database server +to a column with an I<auto_increment> or I<serial> type. +Returns undef if the driver does not support the method or can't +determine the value. + +The $catalog, $schema, $table, and $field parameters may be required +for some drivers (see below). If you don't know the parameter values +and your driver does not need them, then use C<undef> for each. + +There are several caveats to be aware of with this method if you want +to use it for portable applications: + +B<*> For some drivers the value may only available immediately after +the insert statement has executed (e.g., mysql, Informix). + +B<*> For some drivers the $catalog, $schema, $table, and $field parameters +are required, for others they are ignored (e.g., mysql). + +B<*> Drivers may return an indeterminate value if no insert has +been performed yet. + +B<*> For some drivers the value may only be available if placeholders +have I<not> been used (e.g., Sybase, MS SQL). In this case the value +returned would be from the last non-placeholder insert statement. + +B<*> Some drivers may need driver-specific hints about how to get +the value. For example, being told the name of the database 'sequence' +object that holds the value. Any such hints are passed as driver-specific +attributes in the \%attr parameter. + +B<*> If the underlying database offers nothing better, then some +drivers may attempt to implement this method by executing +"C<select max($field) from $table>". Drivers using any approach +like this should issue a warning if C<AutoCommit> is true because +it is generally unsafe - another process may have modified the table +between your insert and the select. For situations where you know +it is safe, such as when you have locked the table, you can silence +the warning by passing C<Warn> => 0 in \%attr. + +B<*> If no insert has been performed yet, or the last insert failed, +then the value is implementation defined. + +Given all the caveats above, it's clear that this method must be +used with care. + +The C<last_insert_id> method was added in DBI 1.38. + +=head3 C<selectrow_array> + + @row_ary = $dbh->selectrow_array($statement); + @row_ary = $dbh->selectrow_array($statement, \%attr); + @row_ary = $dbh->selectrow_array($statement, \%attr, @bind_values); + +This utility method combines L</prepare>, L</execute> and +L</fetchrow_array> into a single call. If called in a list context, it +returns the first row of data from the statement. The C<$statement> +parameter can be a previously prepared statement handle, in which case +the C<prepare> is skipped. + +If any method fails, and L</RaiseError> is not set, C<selectrow_array> +will return an empty list. + +If called in a scalar context for a statement handle that has more +than one column, it is undefined whether the driver will return +the value of the first column or the last. So don't do that. +Also, in a scalar context, an C<undef> is returned if there are no +more rows or if an error occurred. That C<undef> can't be distinguished +from an C<undef> returned because the first field value was NULL. +For these reasons you should exercise some caution if you use +C<selectrow_array> in a scalar context, or just don't do that. + + +=head3 C<selectrow_arrayref> + + $ary_ref = $dbh->selectrow_arrayref($statement); + $ary_ref = $dbh->selectrow_arrayref($statement, \%attr); + $ary_ref = $dbh->selectrow_arrayref($statement, \%attr, @bind_values); + +This utility method combines L</prepare>, L</execute> and +L</fetchrow_arrayref> into a single call. It returns the first row of +data from the statement. The C<$statement> parameter can be a previously +prepared statement handle, in which case the C<prepare> is skipped. + +If any method fails, and L</RaiseError> is not set, C<selectrow_array> +will return undef. + + +=head3 C<selectrow_hashref> + + $hash_ref = $dbh->selectrow_hashref($statement); + $hash_ref = $dbh->selectrow_hashref($statement, \%attr); + $hash_ref = $dbh->selectrow_hashref($statement, \%attr, @bind_values); + +This utility method combines L</prepare>, L</execute> and +L</fetchrow_hashref> into a single call. It returns the first row of +data from the statement. The C<$statement> parameter can be a previously +prepared statement handle, in which case the C<prepare> is skipped. + +If any method fails, and L</RaiseError> is not set, C<selectrow_hashref> +will return undef. + + +=head3 C<selectall_arrayref> + + $ary_ref = $dbh->selectall_arrayref($statement); + $ary_ref = $dbh->selectall_arrayref($statement, \%attr); + $ary_ref = $dbh->selectall_arrayref($statement, \%attr, @bind_values); + +This utility method combines L</prepare>, L</execute> and +L</fetchall_arrayref> into a single call. It returns a reference to an +array containing a reference to an array (or hash, see below) for each row of +data fetched. + +The C<$statement> parameter can be a previously prepared statement handle, +in which case the C<prepare> is skipped. This is recommended if the +statement is going to be executed many times. + +If L</RaiseError> is not set and any method except C<fetchall_arrayref> +fails then C<selectall_arrayref> will return C<undef>; if +C<fetchall_arrayref> fails then it will return with whatever data +has been fetched thus far. You should check C<$sth-E<gt>err> +afterwards (or use the C<RaiseError> attribute) to discover if the data is +complete or was truncated due to an error. + +The L</fetchall_arrayref> method called by C<selectall_arrayref> +supports a $max_rows parameter. You can specify a value for $max_rows +by including a 'C<MaxRows>' attribute in \%attr. In which case finish() +is called for you after fetchall_arrayref() returns. + +The L</fetchall_arrayref> method called by C<selectall_arrayref> +also supports a $slice parameter. You can specify a value for $slice by +including a 'C<Slice>' or 'C<Columns>' attribute in \%attr. The only +difference between the two is that if C<Slice> is not defined and +C<Columns> is an array ref, then the array is assumed to contain column +index values (which count from 1), rather than perl array index values. +In which case the array is copied and each value decremented before +passing to C</fetchall_arrayref>. + +You may often want to fetch an array of rows where each row is stored as a +hash. That can be done simple using: + + my $emps = $dbh->selectall_arrayref( + "SELECT ename FROM emp ORDER BY ename", + { Slice => {} } + ); + foreach my $emp ( @$emps ) { + print "Employee: $emp->{ename}\n"; + } + +Or, to fetch into an array instead of an array ref: + + @result = @{ $dbh->selectall_arrayref($sql, { Slice => {} }) }; + +See L</fetchall_arrayref> method for more details. + +=head3 C<selectall_hashref> + + $hash_ref = $dbh->selectall_hashref($statement, $key_field); + $hash_ref = $dbh->selectall_hashref($statement, $key_field, \%attr); + $hash_ref = $dbh->selectall_hashref($statement, $key_field, \%attr, @bind_values); + +This utility method combines L</prepare>, L</execute> and +L</fetchall_hashref> into a single call. It returns a reference to a +hash containing one entry, at most, for each row, as returned by fetchall_hashref(). + +The C<$statement> parameter can be a previously prepared statement handle, +in which case the C<prepare> is skipped. This is recommended if the +statement is going to be executed many times. + +The C<$key_field> parameter defines which column, or columns, are used as keys +in the returned hash. It can either be the name of a single field, or a +reference to an array containing multiple field names. Using multiple names +yields a tree of nested hashes. + +If a row has the same key as an earlier row then it replaces the earlier row. + +If any method except C<fetchrow_hashref> fails, and L</RaiseError> is not set, +C<selectall_hashref> will return C<undef>. If C<fetchrow_hashref> fails and +L</RaiseError> is not set, then it will return with whatever data it +has fetched thus far. $DBI::err should be checked to catch that. + +See fetchall_hashref() for more details. + +=head3 C<selectcol_arrayref> + + $ary_ref = $dbh->selectcol_arrayref($statement); + $ary_ref = $dbh->selectcol_arrayref($statement, \%attr); + $ary_ref = $dbh->selectcol_arrayref($statement, \%attr, @bind_values); + +This utility method combines L</prepare>, L</execute>, and fetching one +column from all the rows, into a single call. It returns a reference to +an array containing the values of the first column from each row. + +The C<$statement> parameter can be a previously prepared statement handle, +in which case the C<prepare> is skipped. This is recommended if the +statement is going to be executed many times. + +If any method except C<fetch> fails, and L</RaiseError> is not set, +C<selectcol_arrayref> will return C<undef>. If C<fetch> fails and +L</RaiseError> is not set, then it will return with whatever data it +has fetched thus far. $DBI::err should be checked to catch that. + +The C<selectcol_arrayref> method defaults to pushing a single column +value (the first) from each row into the result array. However, it can +also push another column, or even multiple columns per row, into the +result array. This behaviour can be specified via a 'C<Columns>' +attribute which must be a ref to an array containing the column number +or numbers to use. For example: + + # get array of id and name pairs: + my $ary_ref = $dbh->selectcol_arrayref("select id, name from table", { Columns=>[1,2] }); + my %hash = @$ary_ref; # build hash from key-value pairs so $hash{$id} => name + +You can specify a maximum number of rows to fetch by including a +'C<MaxRows>' attribute in \%attr. + +=head3 C<prepare> + + $sth = $dbh->prepare($statement) or die $dbh->errstr; + $sth = $dbh->prepare($statement, \%attr) or die $dbh->errstr; + +Prepares a statement for later execution by the database +engine and returns a reference to a statement handle object. + +The returned statement handle can be used to get attributes of the +statement and invoke the L</execute> method. See L</Statement Handle Methods>. + +Drivers for engines without the concept of preparing a +statement will typically just store the statement in the returned +handle and process it when C<$sth-E<gt>execute> is called. Such drivers are +unlikely to give much useful information about the +statement, such as C<$sth-E<gt>{NUM_OF_FIELDS}>, until after C<$sth-E<gt>execute> +has been called. Portable applications should take this into account. + +In general, DBI drivers do not parse the contents of the statement +(other than simply counting any L</Placeholders>). The statement is +passed directly to the database engine, sometimes known as pass-thru +mode. This has advantages and disadvantages. On the plus side, you can +access all the functionality of the engine being used. On the downside, +you're limited if you're using a simple engine, and you need to take extra care if +writing applications intended to be portable between engines. + +Portable applications should not assume that a new statement can be +prepared and/or executed while still fetching results from a previous +statement. + +Some command-line SQL tools use statement terminators, like a semicolon, +to indicate the end of a statement. Such terminators should not normally +be used with the DBI. + + +=head3 C<prepare_cached> + + $sth = $dbh->prepare_cached($statement) + $sth = $dbh->prepare_cached($statement, \%attr) + $sth = $dbh->prepare_cached($statement, \%attr, $if_active) + +Like L</prepare> except that the statement handle returned will be +stored in a hash associated with the C<$dbh>. If another call is made to +C<prepare_cached> with the same C<$statement> and C<%attr> parameter values, +then the corresponding cached C<$sth> will be returned without contacting the +database server. + +The C<$if_active> parameter lets you adjust the behaviour if an +already cached statement handle is still Active. There are several +alternatives: + +=over 4 + +=item B<0>: A warning will be generated, and finish() will be called on +the statement handle before it is returned. This is the default +behaviour if $if_active is not passed. + +=item B<1>: finish() will be called on the statement handle, but the +warning is suppressed. + +=item B<2>: Disables any checking. + +=item B<3>: The existing active statement handle will be removed from the +cache and a new statement handle prepared and cached in its place. +This is the safest option because it doesn't affect the state of the +old handle, it just removes it from the cache. [Added in DBI 1.40] + +=back + +Here are some examples of C<prepare_cached>: + + sub insert_hash { + my ($table, $field_values) = @_; + # sort to keep field order, and thus sql, stable for prepare_cached + my @fields = sort keys %$field_values; + my @values = @{$field_values}{@fields}; + my $sql = sprintf "insert into %s (%s) values (%s)", + $table, join(",", @fields), join(",", ("?")x@fields); + my $sth = $dbh->prepare_cached($sql); + return $sth->execute(@values); + } + + sub search_hash { + my ($table, $field_values) = @_; + # sort to keep field order, and thus sql, stable for prepare_cached + my @fields = sort keys %$field_values; + my @values = @{$field_values}{@fields}; + my $qualifier = ""; + $qualifier = "where ".join(" and ", map { "$_=?" } @fields) if @fields; + $sth = $dbh->prepare_cached("SELECT * FROM $table $qualifier"); + return $dbh->selectall_arrayref($sth, {}, @values); + } + +I<Caveat emptor:> This caching can be useful in some applications, +but it can also cause problems and should be used with care. Here +is a contrived case where caching would cause a significant problem: + + my $sth = $dbh->prepare_cached('SELECT * FROM foo WHERE bar=?'); + $sth->execute(...); + while (my $data = $sth->fetchrow_hashref) { + + # later, in some other code called within the loop... + my $sth2 = $dbh->prepare_cached('SELECT * FROM foo WHERE bar=?'); + $sth2->execute(...); + while (my $data2 = $sth2->fetchrow_arrayref) { + do_stuff(...); + } + } + +In this example, since both handles are preparing the exact same statement, +C<$sth2> will not be its own statement handle, but a duplicate of C<$sth> +returned from the cache. The results will certainly not be what you expect. +Typically the inner fetch loop will work normally, fetching all +the records and terminating when there are no more, but now that $sth +is the same as $sth2 the outer fetch loop will also terminate. + +You'll know if you run into this problem because prepare_cached() +will generate a warning by default (when $if_active is false). + +The cache used by prepare_cached() is keyed by both the statement +and any attributes so you can also avoid this issue by doing something +like: + + $sth = $dbh->prepare_cached("...", { dbi_dummy => __FILE__.__LINE__ }); + +which will ensure that prepare_cached only returns statements cached +by that line of code in that source file. + +If you'd like the cache to managed intelligently, you can tie the +hashref returned by C<CachedKids> to an appropriate caching module, +such as L<Tie::Cache::LRU>: + + my $cache; + tie %$cache, 'Tie::Cache::LRU', 500; + $dbh->{CachedKids} = $cache; + +=head3 C<commit> + + $rc = $dbh->commit or die $dbh->errstr; + +Commit (make permanent) the most recent series of database changes +if the database supports transactions and AutoCommit is off. + +If C<AutoCommit> is on, then calling +C<commit> will issue a "commit ineffective with AutoCommit" warning. + +See also L</Transactions> in the L</FURTHER INFORMATION> section below. + +=head3 C<rollback> + + $rc = $dbh->rollback or die $dbh->errstr; + +Rollback (undo) the most recent series of uncommitted database +changes if the database supports transactions and AutoCommit is off. + +If C<AutoCommit> is on, then calling +C<rollback> will issue a "rollback ineffective with AutoCommit" warning. + +See also L</Transactions> in the L</FURTHER INFORMATION> section below. + +=head3 C<begin_work> + + $rc = $dbh->begin_work or die $dbh->errstr; + +Enable transactions (by turning C<AutoCommit> off) until the next call +to C<commit> or C<rollback>. After the next C<commit> or C<rollback>, +C<AutoCommit> will automatically be turned on again. + +If C<AutoCommit> is already off when C<begin_work> is called then +it does nothing except return an error. If the driver does not support +transactions then when C<begin_work> attempts to set C<AutoCommit> off +the driver will trigger a fatal error. + +See also L</Transactions> in the L</FURTHER INFORMATION> section below. + + +=head3 C<disconnect> + + $rc = $dbh->disconnect or warn $dbh->errstr; + +Disconnects the database from the database handle. C<disconnect> is typically only used +before exiting the program. The handle is of little use after disconnecting. + +The transaction behaviour of the C<disconnect> method is, sadly, +undefined. Some database systems (such as Oracle and Ingres) will +automatically commit any outstanding changes, but others (such as +Informix) will rollback any outstanding changes. Applications not +using C<AutoCommit> should explicitly call C<commit> or C<rollback> before +calling C<disconnect>. + +The database is automatically disconnected by the C<DESTROY> method if +still connected when there are no longer any references to the handle. +The C<DESTROY> method for each driver should implicitly call C<rollback> to +undo any uncommitted changes. This is vital behaviour to ensure that +incomplete transactions don't get committed simply because Perl calls +C<DESTROY> on every object before exiting. Also, do not rely on the order +of object destruction during "global destruction", as it is undefined. + +Generally, if you want your changes to be committed or rolled back when +you disconnect, then you should explicitly call L</commit> or L</rollback> +before disconnecting. + +If you disconnect from a database while you still have active +statement handles (e.g., SELECT statement handles that may have +more data to fetch), you will get a warning. The warning may indicate +that a fetch loop terminated early, perhaps due to an uncaught error. +To avoid the warning call the C<finish> method on the active handles. + + +=head3 C<ping> + + $rc = $dbh->ping; + +Attempts to determine, in a reasonably efficient way, if the database +server is still running and the connection to it is still working. +Individual drivers should implement this function in the most suitable +manner for their database engine. + +The current I<default> implementation always returns true without +actually doing anything. Actually, it returns "C<0 but true>" which is +true but zero. That way you can tell if the return value is genuine or +just the default. Drivers should override this method with one that +does the right thing for their type of database. + +Few applications would have direct use for this method. See the specialized +Apache::DBI module for one example usage. + + +=head3 C<get_info> + + $value = $dbh->get_info( $info_type ); + +Returns information about the implementation, i.e. driver and data +source capabilities, restrictions etc. It returns C<undef> for +unknown or unimplemented information types. For example: + + $database_version = $dbh->get_info( 18 ); # SQL_DBMS_VER + $max_select_tables = $dbh->get_info( 106 ); # SQL_MAXIMUM_TABLES_IN_SELECT + +See L</"Standards Reference Information"> for more detailed information +about the information types and their meanings and possible return values. + +The DBI::Const::GetInfoType module exports a %GetInfoType hash that +can be used to map info type names to numbers. For example: + + $database_version = $dbh->get_info( $GetInfoType{SQL_DBMS_VER} ); + +The names are a merging of the ANSI and ODBC standards (which differ +in some cases). See L<DBI::Const::GetInfoType> for more details. + +Because some DBI methods make use of get_info(), drivers are strongly +encouraged to support I<at least> the following very minimal set +of information types to ensure the DBI itself works properly: + + Type Name Example A Example B + ---- -------------------------- ------------ ---------------- + 17 SQL_DBMS_NAME 'ACCESS' 'Oracle' + 18 SQL_DBMS_VER '03.50.0000' '08.01.0721 ...' + 29 SQL_IDENTIFIER_QUOTE_CHAR '`' '"' + 41 SQL_CATALOG_NAME_SEPARATOR '.' '@' + 114 SQL_CATALOG_LOCATION 1 2 + +=head3 C<table_info> + + $sth = $dbh->table_info( $catalog, $schema, $table, $type ); + $sth = $dbh->table_info( $catalog, $schema, $table, $type, \%attr ); + + # then $sth->fetchall_arrayref or $sth->fetchall_hashref etc + +Returns an active statement handle that can be used to fetch +information about tables and views that exist in the database. + +The arguments $catalog, $schema and $table may accept search patterns +according to the database/driver, for example: $table = '%FOO%'; +Remember that the underscore character ('C<_>') is a search pattern +that means match any character, so 'FOO_%' is the same as 'FOO%' +and 'FOO_BAR%' will match names like 'FOO1BAR'. + +The value of $type is a comma-separated list of one or more types of +tables to be returned in the result set. Each value may optionally be +quoted, e.g.: + + $type = "TABLE"; + $type = "'TABLE','VIEW'"; + +In addition the following special cases may also be supported by some drivers: + +=over 4 + +=item * +If the value of $catalog is '%' and $schema and $table name +are empty strings, the result set contains a list of catalog names. +For example: + + $sth = $dbh->table_info('%', '', ''); + +=item * +If the value of $schema is '%' and $catalog and $table are empty +strings, the result set contains a list of schema names. + +=item * +If the value of $type is '%' and $catalog, $schema, and $table are all +empty strings, the result set contains a list of table types. + +=back + +If your driver doesn't support one or more of the selection filter +parameters then you may get back more than you asked for and can +do the filtering yourself. + +This method can be expensive, and can return a large amount of data. +(For example, small Oracle installation returns over 2000 rows.) +So it's a good idea to use the filters to limit the data as much as possible. + +The statement handle returned has at least the following fields in the +order show below. Other fields, after these, may also be present. + +B<TABLE_CAT>: Table catalog identifier. This field is NULL (C<undef>) if not +applicable to the data source, which is usually the case. This field +is empty if not applicable to the table. + +B<TABLE_SCHEM>: The name of the schema containing the TABLE_NAME value. +This field is NULL (C<undef>) if not applicable to data source, and +empty if not applicable to the table. + +B<TABLE_NAME>: Name of the table (or view, synonym, etc). + +B<TABLE_TYPE>: One of the following: "TABLE", "VIEW", "SYSTEM TABLE", +"GLOBAL TEMPORARY", "LOCAL TEMPORARY", "ALIAS", "SYNONYM" or a type +identifier that is specific to the data +source. + +B<REMARKS>: A description of the table. May be NULL (C<undef>). + +Note that C<table_info> might not return records for all tables. +Applications can use any valid table regardless of whether it's +returned by C<table_info>. + +See also L</tables>, L</"Catalog Methods"> and +L</"Standards Reference Information">. + +=head3 C<column_info> + + $sth = $dbh->column_info( $catalog, $schema, $table, $column ); + + # then $sth->fetchall_arrayref or $sth->fetchall_hashref etc + +Returns an active statement handle that can be used to fetch +information about columns in specified tables. + +The arguments $schema, $table and $column may accept search patterns +according to the database/driver, for example: $table = '%FOO%'; + +Note: The support for the selection criteria is driver specific. If the +driver doesn't support one or more of them then you may get back more +than you asked for and can do the filtering yourself. + +Note: If your driver does not support column_info an undef is +returned. This is distinct from asking for something which does not +exist in a driver which supports column_info as a valid statement +handle to an empty result-set will be returned in this case. + +If the arguments don't match any tables then you'll still get a statement +handle, it'll just return no rows. + +The statement handle returned has at least the following fields in the +order shown below. Other fields, after these, may also be present. + +B<TABLE_CAT>: The catalog identifier. +This field is NULL (C<undef>) if not applicable to the data source, +which is often the case. This field is empty if not applicable to the +table. + +B<TABLE_SCHEM>: The schema identifier. +This field is NULL (C<undef>) if not applicable to the data source, +and empty if not applicable to the table. + +B<TABLE_NAME>: The table identifier. +Note: A driver may provide column metadata not only for base tables, but +also for derived objects like SYNONYMS etc. + +B<COLUMN_NAME>: The column identifier. + +B<DATA_TYPE>: The concise data type code. + +B<TYPE_NAME>: A data source dependent data type name. + +B<COLUMN_SIZE>: The column size. +This is the maximum length in characters for character data types, +the number of digits or bits for numeric data types or the length +in the representation of temporal types. +See the relevant specifications for detailed information. + +B<BUFFER_LENGTH>: The length in bytes of transferred data. + +B<DECIMAL_DIGITS>: The total number of significant digits to the right of +the decimal point. + +B<NUM_PREC_RADIX>: The radix for numeric precision. +The value is 10 or 2 for numeric data types and NULL (C<undef>) if not +applicable. + +B<NULLABLE>: Indicates if a column can accept NULLs. +The following values are defined: + + SQL_NO_NULLS 0 + SQL_NULLABLE 1 + SQL_NULLABLE_UNKNOWN 2 + +B<REMARKS>: A description of the column. + +B<COLUMN_DEF>: The default value of the column, in a format that can be used +directly in an SQL statement. + +Note that this may be an expression and not simply the text used for the +default value in the original CREATE TABLE statement. For example, given: + + col1 char(30) default current_user -- a 'function' + col2 char(30) default 'string' -- a string literal + +where "current_user" is the name of a function, the corresponding C<COLUMN_DEF> +values would be: + + Database col1 col2 + -------- ---- ---- + Oracle: current_user 'string' + Postgres: "current_user"() 'string'::text + MS SQL: (user_name()) ('string') + +B<SQL_DATA_TYPE>: The SQL data type. + +B<SQL_DATETIME_SUB>: The subtype code for datetime and interval data types. + +B<CHAR_OCTET_LENGTH>: The maximum length in bytes of a character or binary +data type column. + +B<ORDINAL_POSITION>: The column sequence number (starting with 1). + +B<IS_NULLABLE>: Indicates if the column can accept NULLs. +Possible values are: 'NO', 'YES' and ''. + +SQL/CLI defines the following additional columns: + + CHAR_SET_CAT + CHAR_SET_SCHEM + CHAR_SET_NAME + COLLATION_CAT + COLLATION_SCHEM + COLLATION_NAME + UDT_CAT + UDT_SCHEM + UDT_NAME + DOMAIN_CAT + DOMAIN_SCHEM + DOMAIN_NAME + SCOPE_CAT + SCOPE_SCHEM + SCOPE_NAME + MAX_CARDINALITY + DTD_IDENTIFIER + IS_SELF_REF + +Drivers capable of supplying any of those values should do so in +the corresponding column and supply undef values for the others. + +Drivers wishing to provide extra database/driver specific information +should do so in extra columns beyond all those listed above, and +use lowercase field names with the driver-specific prefix (i.e., +'ora_...'). Applications accessing such fields should do so by name +and not by column number. + +The result set is ordered by TABLE_CAT, TABLE_SCHEM, TABLE_NAME +and ORDINAL_POSITION. + +Note: There is some overlap with statement handle attributes (in perl) and +SQLDescribeCol (in ODBC). However, SQLColumns provides more metadata. + +See also L</"Catalog Methods"> and L</"Standards Reference Information">. + +=head3 C<primary_key_info> + + $sth = $dbh->primary_key_info( $catalog, $schema, $table ); + + # then $sth->fetchall_arrayref or $sth->fetchall_hashref etc + +Returns an active statement handle that can be used to fetch information +about columns that make up the primary key for a table. +The arguments don't accept search patterns (unlike table_info()). + +The statement handle will return one row per column, ordered by +TABLE_CAT, TABLE_SCHEM, TABLE_NAME, and KEY_SEQ. +If there is no primary key then the statement handle will fetch no rows. + +Note: The support for the selection criteria, such as $catalog, is +driver specific. If the driver doesn't support catalogs and/or +schemas, it may ignore these criteria. + +The statement handle returned has at least the following fields in the +order shown below. Other fields, after these, may also be present. + +B<TABLE_CAT>: The catalog identifier. +This field is NULL (C<undef>) if not applicable to the data source, +which is often the case. This field is empty if not applicable to the +table. + +B<TABLE_SCHEM>: The schema identifier. +This field is NULL (C<undef>) if not applicable to the data source, +and empty if not applicable to the table. + +B<TABLE_NAME>: The table identifier. + +B<COLUMN_NAME>: The column identifier. + +B<KEY_SEQ>: The column sequence number (starting with 1). +Note: This field is named B<ORDINAL_POSITION> in SQL/CLI. + +B<PK_NAME>: The primary key constraint identifier. +This field is NULL (C<undef>) if not applicable to the data source. + +See also L</"Catalog Methods"> and L</"Standards Reference Information">. + +=head3 C<primary_key> + + @key_column_names = $dbh->primary_key( $catalog, $schema, $table ); + +Simple interface to the primary_key_info() method. Returns a list of +the column names that comprise the primary key of the specified table. +The list is in primary key column sequence order. +If there is no primary key then an empty list is returned. + +=head3 C<foreign_key_info> + + $sth = $dbh->foreign_key_info( $pk_catalog, $pk_schema, $pk_table + , $fk_catalog, $fk_schema, $fk_table ); + + $sth = $dbh->foreign_key_info( $pk_catalog, $pk_schema, $pk_table + , $fk_catalog, $fk_schema, $fk_table + , \%attr ); + + # then $sth->fetchall_arrayref or $sth->fetchall_hashref etc + +Returns an active statement handle that can be used to fetch information +about foreign keys in and/or referencing the specified table(s). +The arguments don't accept search patterns (unlike table_info()). + +C<$pk_catalog>, C<$pk_schema>, C<$pk_table> +identify the primary (unique) key table (B<PKT>). + +C<$fk_catalog>, C<$fk_schema>, C<$fk_table> +identify the foreign key table (B<FKT>). + +If both B<PKT> and B<FKT> are given, the function returns the foreign key, if +any, in table B<FKT> that refers to the primary (unique) key of table B<PKT>. +(Note: In SQL/CLI, the result is implementation-defined.) + +If only B<PKT> is given, then the result set contains the primary key +of that table and all foreign keys that refer to it. + +If only B<FKT> is given, then the result set contains all foreign keys +in that table and the primary keys to which they refer. +(Note: In SQL/CLI, the result includes unique keys too.) + +For example: + + $sth = $dbh->foreign_key_info( undef, $user, 'master'); + $sth = $dbh->foreign_key_info( undef, undef, undef , undef, $user, 'detail'); + $sth = $dbh->foreign_key_info( undef, $user, 'master', undef, $user, 'detail'); + + # then $sth->fetchall_arrayref or $sth->fetchall_hashref etc + +Note: The support for the selection criteria, such as C<$catalog>, is +driver specific. If the driver doesn't support catalogs and/or +schemas, it may ignore these criteria. + +The statement handle returned has the following fields in the order shown below. +Because ODBC never includes unique keys, they define different columns in the +result set than SQL/CLI. SQL/CLI column names are shown in parentheses. + +B<PKTABLE_CAT ( UK_TABLE_CAT )>: +The primary (unique) key table catalog identifier. +This field is NULL (C<undef>) if not applicable to the data source, +which is often the case. This field is empty if not applicable to the +table. + +B<PKTABLE_SCHEM ( UK_TABLE_SCHEM )>: +The primary (unique) key table schema identifier. +This field is NULL (C<undef>) if not applicable to the data source, +and empty if not applicable to the table. + +B<PKTABLE_NAME ( UK_TABLE_NAME )>: +The primary (unique) key table identifier. + +B<PKCOLUMN_NAME (UK_COLUMN_NAME )>: +The primary (unique) key column identifier. + +B<FKTABLE_CAT ( FK_TABLE_CAT )>: +The foreign key table catalog identifier. +This field is NULL (C<undef>) if not applicable to the data source, +which is often the case. This field is empty if not applicable to the +table. + +B<FKTABLE_SCHEM ( FK_TABLE_SCHEM )>: +The foreign key table schema identifier. +This field is NULL (C<undef>) if not applicable to the data source, +and empty if not applicable to the table. + +B<FKTABLE_NAME ( FK_TABLE_NAME )>: +The foreign key table identifier. + +B<FKCOLUMN_NAME ( FK_COLUMN_NAME )>: +The foreign key column identifier. + +B<KEY_SEQ ( ORDINAL_POSITION )>: +The column sequence number (starting with 1). + +B<UPDATE_RULE ( UPDATE_RULE )>: +The referential action for the UPDATE rule. +The following codes are defined: + + CASCADE 0 + RESTRICT 1 + SET NULL 2 + NO ACTION 3 + SET DEFAULT 4 + +B<DELETE_RULE ( DELETE_RULE )>: +The referential action for the DELETE rule. +The codes are the same as for UPDATE_RULE. + +B<FK_NAME ( FK_NAME )>: +The foreign key name. + +B<PK_NAME ( UK_NAME )>: +The primary (unique) key name. + +B<DEFERRABILITY ( DEFERABILITY )>: +The deferrability of the foreign key constraint. +The following codes are defined: + + INITIALLY DEFERRED 5 + INITIALLY IMMEDIATE 6 + NOT DEFERRABLE 7 + +B< ( UNIQUE_OR_PRIMARY )>: +This column is necessary if a driver includes all candidate (i.e. primary and +alternate) keys in the result set (as specified by SQL/CLI). +The value of this column is UNIQUE if the foreign key references an alternate +key and PRIMARY if the foreign key references a primary key, or it +may be undefined if the driver doesn't have access to the information. + +See also L</"Catalog Methods"> and L</"Standards Reference Information">. + +=head3 C<statistics_info> + +B<Warning:> This method is experimental and may change. + + $sth = $dbh->statistics_info( $catalog, $schema, $table, $unique_only, $quick ); + + # then $sth->fetchall_arrayref or $sth->fetchall_hashref etc + +Returns an active statement handle that can be used to fetch statistical +information about a table and its indexes. + +The arguments don't accept search patterns (unlike L</table_info>). + +If the boolean argument $unique_only is true, only UNIQUE indexes will be +returned in the result set, otherwise all indexes will be returned. + +If the boolean argument $quick is set, the actual statistical information +columns (CARDINALITY and PAGES) will only be returned if they are readily +available from the server, and might not be current. Some databases may +return stale statistics or no statistics at all with this flag set. + +The statement handle will return at most one row per column name per index, +plus at most one row for the entire table itself, ordered by NON_UNIQUE, TYPE, +INDEX_QUALIFIER, INDEX_NAME, and ORDINAL_POSITION. + +Note: The support for the selection criteria, such as $catalog, is +driver specific. If the driver doesn't support catalogs and/or +schemas, it may ignore these criteria. + +The statement handle returned has at least the following fields in the +order shown below. Other fields, after these, may also be present. + +B<TABLE_CAT>: The catalog identifier. +This field is NULL (C<undef>) if not applicable to the data source, +which is often the case. This field is empty if not applicable to the +table. + +B<TABLE_SCHEM>: The schema identifier. +This field is NULL (C<undef>) if not applicable to the data source, +and empty if not applicable to the table. + +B<TABLE_NAME>: The table identifier. + +B<NON_UNIQUE>: Unique index indicator. +Returns 0 for unique indexes, 1 for non-unique indexes + +B<INDEX_QUALIFIER>: Index qualifier identifier. +The identifier that is used to qualify the index name when doing a +C<DROP INDEX>; NULL (C<undef>) is returned if an index qualifier is not +supported by the data source. +If a non-NULL (defined) value is returned in this column, it must be used +to qualify the index name on a C<DROP INDEX> statement; otherwise, +the TABLE_SCHEM should be used to qualify the index name. + +B<INDEX_NAME>: The index identifier. + +B<TYPE>: The type of information being returned. Can be any of the +following values: 'table', 'btree', 'clustered', 'content', 'hashed', +or 'other'. + +In the case that this field is 'table', all fields +other than TABLE_CAT, TABLE_SCHEM, TABLE_NAME, TYPE, +CARDINALITY, and PAGES will be NULL (C<undef>). + +B<ORDINAL_POSITION>: Column sequence number (starting with 1). + +B<COLUMN_NAME>: The column identifier. + +B<ASC_OR_DESC>: Column sort sequence. +C<A> for Ascending, C<D> for Descending, or NULL (C<undef>) if +not supported for this index. + +B<CARDINALITY>: Cardinality of the table or index. +For indexes, this is the number of unique values in the index. +For tables, this is the number of rows in the table. +If not supported, the value will be NULL (C<undef>). + +B<PAGES>: Number of storage pages used by this table or index. +If not supported, the value will be NULL (C<undef>). + +B<FILTER_CONDITION>: The index filter condition as a string. +If the index is not a filtered index, or it cannot be determined +whether the index is a filtered index, this value is NULL (C<undef>). +If the index is a filtered index, but the filter condition +cannot be determined, this value is the empty string C<''>. +Otherwise it will be the literal filter condition as a string, +such as C<SALARY <= 4500>. + +See also L</"Catalog Methods"> and L</"Standards Reference Information">. + +=head3 C<tables> + + @names = $dbh->tables( $catalog, $schema, $table, $type ); + @names = $dbh->tables; # deprecated + +Simple interface to table_info(). Returns a list of matching +table names, possibly including a catalog/schema prefix. + +See L</table_info> for a description of the parameters. + +If C<$dbh-E<gt>get_info(29)> returns true (29 is SQL_IDENTIFIER_QUOTE_CHAR) +then the table names are constructed and quoted by L</quote_identifier> +to ensure they are usable even if they contain whitespace or reserved +words etc. This means that the table names returned will include +quote characters. + +=head3 C<type_info_all> + + $type_info_all = $dbh->type_info_all; + +Returns a reference to an array which holds information about each data +type variant supported by the database and driver. The array and its +contents should be treated as read-only. + +The first item is a reference to an 'index' hash of C<Name =>E<gt> C<Index> pairs. +The items following that are references to arrays, one per supported data +type variant. The leading index hash defines the names and order of the +fields within the arrays that follow it. +For example: + + $type_info_all = [ + { TYPE_NAME => 0, + DATA_TYPE => 1, + COLUMN_SIZE => 2, # was PRECISION originally + LITERAL_PREFIX => 3, + LITERAL_SUFFIX => 4, + CREATE_PARAMS => 5, + NULLABLE => 6, + CASE_SENSITIVE => 7, + SEARCHABLE => 8, + UNSIGNED_ATTRIBUTE=> 9, + FIXED_PREC_SCALE => 10, # was MONEY originally + AUTO_UNIQUE_VALUE => 11, # was AUTO_INCREMENT originally + LOCAL_TYPE_NAME => 12, + MINIMUM_SCALE => 13, + MAXIMUM_SCALE => 14, + SQL_DATA_TYPE => 15, + SQL_DATETIME_SUB => 16, + NUM_PREC_RADIX => 17, + INTERVAL_PRECISION=> 18, + }, + [ 'VARCHAR', SQL_VARCHAR, + undef, "'","'", undef,0, 1,1,0,0,0,undef,1,255, undef + ], + [ 'INTEGER', SQL_INTEGER, + undef, "", "", undef,0, 0,1,0,0,0,undef,0, 0, 10 + ], + ]; + +More than one row may have the same value in the C<DATA_TYPE> +field if there are different ways to spell the type name and/or there +are variants of the type with different attributes (e.g., with and +without C<AUTO_UNIQUE_VALUE> set, with and without C<UNSIGNED_ATTRIBUTE>, etc). + +The rows are ordered by C<DATA_TYPE> first and then by how closely each +type maps to the corresponding ODBC SQL data type, closest first. + +The meaning of the fields is described in the documentation for +the L</type_info> method. + +An 'index' hash is provided so you don't need to rely on index +values defined above. However, using DBD::ODBC with some old ODBC +drivers may return older names, shown as comments in the example above. +Another issue with the index hash is that the lettercase of the +keys is not defined. It is usually uppercase, as show here, but +drivers may return names with any lettercase. + +Drivers are also free to return extra driver-specific columns of +information - though it's recommended that they start at column +index 50 to leave room for expansion of the DBI/ODBC specification. + +The type_info_all() method is not normally used directly. +The L</type_info> method provides a more usable and useful interface +to the data. + +=head3 C<type_info> + + @type_info = $dbh->type_info($data_type); + +Returns a list of hash references holding information about one or more +variants of $data_type. The list is ordered by C<DATA_TYPE> first and +then by how closely each type maps to the corresponding ODBC SQL data +type, closest first. If called in a scalar context then only the first +(best) element is returned. + +If $data_type is undefined or C<SQL_ALL_TYPES>, then the list will +contain hashes for all data type variants supported by the database and driver. + +If $data_type is an array reference then C<type_info> returns the +information for the I<first> type in the array that has any matches. + +The keys of the hash follow the same letter case conventions as the +rest of the DBI (see L</Naming Conventions and Name Space>). The +following uppercase items should always exist, though may be undef: + +=over 4 + +=item TYPE_NAME (string) + +Data type name for use in CREATE TABLE statements etc. + +=item DATA_TYPE (integer) + +SQL data type number. + +=item COLUMN_SIZE (integer) + +For numeric types, this is either the total number of digits (if the +NUM_PREC_RADIX value is 10) or the total number of bits allowed in the +column (if NUM_PREC_RADIX is 2). + +For string types, this is the maximum size of the string in characters. + +For date and interval types, this is the maximum number of characters +needed to display the value. + +=item LITERAL_PREFIX (string) + +Characters used to prefix a literal. A typical prefix is "C<'>" for characters, +or possibly "C<0x>" for binary values passed as hexadecimal. NULL (C<undef>) is +returned for data types for which this is not applicable. + + +=item LITERAL_SUFFIX (string) + +Characters used to suffix a literal. Typically "C<'>" for characters. +NULL (C<undef>) is returned for data types where this is not applicable. + +=item CREATE_PARAMS (string) + +Parameter names for data type definition. For example, C<CREATE_PARAMS> for a +C<DECIMAL> would be "C<precision,scale>" if the DECIMAL type should be +declared as C<DECIMAL(>I<precision,scale>C<)> where I<precision> and I<scale> +are integer values. For a C<VARCHAR> it would be "C<max length>". +NULL (C<undef>) is returned for data types for which this is not applicable. + +=item NULLABLE (integer) + +Indicates whether the data type accepts a NULL value: +C<0> or an empty string = no, C<1> = yes, C<2> = unknown. + +=item CASE_SENSITIVE (boolean) + +Indicates whether the data type is case sensitive in collations and +comparisons. + +=item SEARCHABLE (integer) + +Indicates how the data type can be used in a WHERE clause, as +follows: + + 0 - Cannot be used in a WHERE clause + 1 - Only with a LIKE predicate + 2 - All comparison operators except LIKE + 3 - Can be used in a WHERE clause with any comparison operator + +=item UNSIGNED_ATTRIBUTE (boolean) + +Indicates whether the data type is unsigned. NULL (C<undef>) is returned +for data types for which this is not applicable. + +=item FIXED_PREC_SCALE (boolean) + +Indicates whether the data type always has the same precision and scale +(such as a money type). NULL (C<undef>) is returned for data types +for which +this is not applicable. + +=item AUTO_UNIQUE_VALUE (boolean) + +Indicates whether a column of this data type is automatically set to a +unique value whenever a new row is inserted. NULL (C<undef>) is returned +for data types for which this is not applicable. + +=item LOCAL_TYPE_NAME (string) + +Localized version of the C<TYPE_NAME> for use in dialog with users. +NULL (C<undef>) is returned if a localized name is not available (in which +case C<TYPE_NAME> should be used). + +=item MINIMUM_SCALE (integer) + +The minimum scale of the data type. If a data type has a fixed scale, +then C<MAXIMUM_SCALE> holds the same value. NULL (C<undef>) is returned for +data types for which this is not applicable. + +=item MAXIMUM_SCALE (integer) + +The maximum scale of the data type. If a data type has a fixed scale, +then C<MINIMUM_SCALE> holds the same value. NULL (C<undef>) is returned for +data types for which this is not applicable. + +=item SQL_DATA_TYPE (integer) + +This column is the same as the C<DATA_TYPE> column, except for interval +and datetime data types. For interval and datetime data types, the +C<SQL_DATA_TYPE> field will return C<SQL_INTERVAL> or C<SQL_DATETIME>, and the +C<SQL_DATETIME_SUB> field below will return the subcode for the specific +interval or datetime data type. If this field is NULL, then the driver +does not support or report on interval or datetime subtypes. + +=item SQL_DATETIME_SUB (integer) + +For interval or datetime data types, where the C<SQL_DATA_TYPE> +field above is C<SQL_INTERVAL> or C<SQL_DATETIME>, this field will +hold the I<subcode> for the specific interval or datetime data type. +Otherwise it will be NULL (C<undef>). + +Although not mentioned explicitly in the standards, it seems there +is a simple relationship between these values: + + DATA_TYPE == (10 * SQL_DATA_TYPE) + SQL_DATETIME_SUB + +=item NUM_PREC_RADIX (integer) + +The radix value of the data type. For approximate numeric types, +C<NUM_PREC_RADIX> +contains the value 2 and C<COLUMN_SIZE> holds the number of bits. For +exact numeric types, C<NUM_PREC_RADIX> contains the value 10 and C<COLUMN_SIZE> holds +the number of decimal digits. NULL (C<undef>) is returned either for data types +for which this is not applicable or if the driver cannot report this information. + +=item INTERVAL_PRECISION (integer) + +The interval leading precision for interval types. NULL is returned +either for data types for which this is not applicable or if the driver +cannot report this information. + +=back + +For example, to find the type name for the fields in a select statement +you can do: + + @names = map { scalar $dbh->type_info($_)->{TYPE_NAME} } @{ $sth->{TYPE} } + +Since DBI and ODBC drivers vary in how they map their types into the +ISO standard types you may need to search for more than one type. +Here's an example looking for a usable type to store a date: + + $my_date_type = $dbh->type_info( [ SQL_DATE, SQL_TIMESTAMP ] ); + +Similarly, to more reliably find a type to store small integers, you could +use a list starting with C<SQL_SMALLINT>, C<SQL_INTEGER>, C<SQL_DECIMAL>, etc. + +See also L</"Standards Reference Information">. + + +=head3 C<quote> + + $sql = $dbh->quote($value); + $sql = $dbh->quote($value, $data_type); + +Quote a string literal for use as a literal value in an SQL statement, +by escaping any special characters (such as quotation marks) +contained within the string and adding the required type of outer +quotation marks. + + $sql = sprintf "SELECT foo FROM bar WHERE baz = %s", + $dbh->quote("Don't"); + +For most database types, at least those that conform to SQL standards, quote +would return C<'Don''t'> (including the outer quotation marks). For others it +may return something like C<'Don\'t'> + +An undefined C<$value> value will be returned as the string C<NULL> (without +single quotation marks) to match how NULLs are represented in SQL. + +If C<$data_type> is supplied, it is used to try to determine the required +quoting behaviour by using the information returned by L</type_info>. +As a special case, the standard numeric types are optimized to return +C<$value> without calling C<type_info>. + +Quote will probably I<not> be able to deal with all possible input +(such as binary data or data containing newlines), and is not related in +any way with escaping or quoting shell meta-characters. + +It is valid for the quote() method to return an SQL expression that +evaluates to the desired string. For example: + + $quoted = $dbh->quote("one\ntwo\0three") + +may return something like: + + CONCAT('one', CHAR(12), 'two', CHAR(0), 'three') + +The quote() method should I<not> be used with L</"Placeholders and +Bind Values">. + +=head3 C<quote_identifier> + + $sql = $dbh->quote_identifier( $name ); + $sql = $dbh->quote_identifier( $catalog, $schema, $table, \%attr ); + +Quote an identifier (table name etc.) for use in an SQL statement, +by escaping any special characters (such as double quotation marks) +it contains and adding the required type of outer quotation marks. + +Undefined names are ignored and the remainder are quoted and then +joined together, typically with a dot (C<.>) character. For example: + + $id = $dbh->quote_identifier( undef, 'Her schema', 'My table' ); + +would, for most database types, return C<"Her schema"."My table"> +(including all the double quotation marks). + +If three names are supplied then the first is assumed to be a +catalog name and special rules may be applied based on what L</get_info> +returns for SQL_CATALOG_NAME_SEPARATOR (41) and SQL_CATALOG_LOCATION (114). +For example, for Oracle: + + $id = $dbh->quote_identifier( 'link', 'schema', 'table' ); + +would return C<"schema"."table"@"link">. + +=head3 C<take_imp_data> + + $imp_data = $dbh->take_imp_data; + +Leaves the $dbh in an almost dead, zombie-like, state and returns +a binary string of raw implementation data from the driver which +describes the current database connection. Effectively it detaches +the underlying database API connection data from the DBI handle. +After calling take_imp_data(), all other methods except C<DESTROY> +will generate a warning and return undef. + +Why would you want to do this? You don't, forget I even mentioned it. +Unless, that is, you're implementing something advanced like a +multi-threaded connection pool. See L<DBI::Pool>. + +The returned $imp_data can be passed as a C<dbi_imp_data> attribute +to a later connect() call, even in a separate thread in the same +process, where the driver can use it to 'adopt' the existing +connection that the implementation data was taken from. + +Some things to keep in mind... + +B<*> the $imp_data holds the only reference to the underlying +database API connection data. That connection is still 'live' and +won't be cleaned up properly unless the $imp_data is used to create +a new $dbh which is then allowed to disconnect() normally. + +B<*> using the same $imp_data to create more than one other new +$dbh at a time may well lead to unpleasant problems. Don't do that. + +Any child statement handles are effectively destroyed when take_imp_data() is +called. + +The C<take_imp_data> method was added in DBI 1.36 but wasn't useful till 1.49. + + +=head2 Database Handle Attributes + +This section describes attributes specific to database handles. + +Changes to these database handle attributes do not affect any other +existing or future database handles. + +Attempting to set or get the value of an unknown attribute generates a warning, +except for private driver-specific attributes (which all have names +starting with a lowercase letter). + +Example: + + $h->{AutoCommit} = ...; # set/write + ... = $h->{AutoCommit}; # get/read + +=head3 C<AutoCommit> + +Type: boolean + +If true, then database changes cannot be rolled-back (undone). If false, +then database changes automatically occur within a "transaction", which +must either be committed or rolled back using the C<commit> or C<rollback> +methods. + +Drivers should always default to C<AutoCommit> mode (an unfortunate +choice largely forced on the DBI by ODBC and JDBC conventions.) + +Attempting to set C<AutoCommit> to an unsupported value is a fatal error. +This is an important feature of the DBI. Applications that need +full transaction behaviour can set C<$dbh-E<gt>{AutoCommit} = 0> (or +set C<AutoCommit> to 0 via L</connect>) +without having to check that the value was assigned successfully. + +For the purposes of this description, we can divide databases into three +categories: + + Databases which don't support transactions at all. + Databases in which a transaction is always active. + Databases in which a transaction must be explicitly started (C<'BEGIN WORK'>). + +B<* Databases which don't support transactions at all> + +For these databases, attempting to turn C<AutoCommit> off is a fatal error. +C<commit> and C<rollback> both issue warnings about being ineffective while +C<AutoCommit> is in effect. + +B<* Databases in which a transaction is always active> + +These are typically mainstream commercial relational databases with +"ANSI standard" transaction behaviour. +If C<AutoCommit> is off, then changes to the database won't have any +lasting effect unless L</commit> is called (but see also +L</disconnect>). If L</rollback> is called then any changes since the +last commit are undone. + +If C<AutoCommit> is on, then the effect is the same as if the DBI +called C<commit> automatically after every successful database +operation. So calling C<commit> or C<rollback> explicitly while +C<AutoCommit> is on would be ineffective because the changes would +have already been committed. + +Changing C<AutoCommit> from off to on will trigger a L</commit>. + +For databases which don't support a specific auto-commit mode, the +driver has to commit each statement automatically using an explicit +C<COMMIT> after it completes successfully (and roll it back using an +explicit C<ROLLBACK> if it fails). The error information reported to the +application will correspond to the statement which was executed, unless +it succeeded and the commit or rollback failed. + +B<* Databases in which a transaction must be explicitly started> + +For these databases, the intention is to have them act like databases in +which a transaction is always active (as described above). + +To do this, the driver will automatically begin an explicit transaction +when C<AutoCommit> is turned off, or after a L</commit> or +L</rollback> (or when the application issues the next database +operation after one of those events). + +In this way, the application does not have to treat these databases +as a special case. + +See L</commit>, L</disconnect> and L</Transactions> for other important +notes about transactions. + + +=head3 C<Driver> + +Type: handle + +Holds the handle of the parent driver. The only recommended use for this +is to find the name of the driver using: + + $dbh->{Driver}->{Name} + + +=head3 C<Name> + +Type: string + +Holds the "name" of the database. Usually (and recommended to be) the +same as the "C<dbi:DriverName:...>" string used to connect to the database, +but with the leading "C<dbi:DriverName:>" removed. + + +=head3 C<Statement> + +Type: string, read-only + +Returns the statement string passed to the most recent L</prepare> or +L</do> method called in this database handle, even if that method +failed. This is especially useful where C<RaiseError> is enabled and +the exception handler checks $@ and sees that a 'prepare' method call +failed. + + +=head3 C<RowCacheSize> + +Type: integer + +A hint to the driver indicating the size of the local row cache that the +application would like the driver to use for future C<SELECT> statements. +If a row cache is not implemented, then setting C<RowCacheSize> is ignored +and getting the value returns C<undef>. + +Some C<RowCacheSize> values have special meaning, as follows: + + 0 - Automatically determine a reasonable cache size for each C<SELECT> + 1 - Disable the local row cache + >1 - Cache this many rows + <0 - Cache as many rows that will fit into this much memory for each C<SELECT>. + +Note that large cache sizes may require a very large amount of memory +(I<cached rows * maximum size of row>). Also, a large cache will cause +a longer delay not only for the first fetch, but also whenever the +cache needs refilling. + +See also the L</RowsInCache> statement handle attribute. + +=head3 C<Username> + +Type: string + +Returns the username used to connect to the database. + + +=head1 DBI STATEMENT HANDLE OBJECTS + +This section lists the methods and attributes associated with DBI +statement handles. + +=head2 Statement Handle Methods + +The DBI defines the following methods for use on DBI statement handles: + +=head3 C<bind_param> + + $sth->bind_param($p_num, $bind_value) + $sth->bind_param($p_num, $bind_value, \%attr) + $sth->bind_param($p_num, $bind_value, $bind_type) + +The C<bind_param> method takes a copy of $bind_value and associates it +(binds it) with a placeholder, identified by $p_num, embedded in +the prepared statement. Placeholders are indicated with question +mark character (C<?>). For example: + + $dbh->{RaiseError} = 1; # save having to check each method call + $sth = $dbh->prepare("SELECT name, age FROM people WHERE name LIKE ?"); + $sth->bind_param(1, "John%"); # placeholders are numbered from 1 + $sth->execute; + DBI::dump_results($sth); + +See L</"Placeholders and Bind Values"> for more information. + + +B<Data Types for Placeholders> + +The C<\%attr> parameter can be used to hint at the data type the +placeholder should have. This is rarely needed. Typically, the driver is only +interested in knowing if the placeholder should be bound as a number or a string. + + $sth->bind_param(1, $value, { TYPE => SQL_INTEGER }); + +As a short-cut for the common case, the data type can be passed +directly, in place of the C<\%attr> hash reference. This example is +equivalent to the one above: + + $sth->bind_param(1, $value, SQL_INTEGER); + +The C<TYPE> value indicates the standard (non-driver-specific) type for +this parameter. To specify the driver-specific type, the driver may +support a driver-specific attribute, such as C<{ ora_type =E<gt> 97 }>. + +The SQL_INTEGER and other related constants can be imported using + + use DBI qw(:sql_types); + +See L</"DBI Constants"> for more information. + +The data type is 'sticky' in that bind values passed to execute() are bound +with the data type specified by earlier bind_param() calls, if any. +Portable applications should not rely on being able to change the data type +after the first C<bind_param> call. + +Perl only has string and number scalar data types. All database types +that aren't numbers are bound as strings and must be in a format the +database will understand except where the bind_param() TYPE attribute +specifies a type that implies a particular format. For example, given: + + $sth->bind_param(1, $value, SQL_DATETIME); + +the driver should expect $value to be in the ODBC standard SQL_DATETIME +format, which is 'YYYY-MM-DD HH:MM:SS'. Similarly for SQL_DATE, SQL_TIME etc. + +As an alternative to specifying the data type in the C<bind_param> call, +you can let the driver pass the value as the default type (C<VARCHAR>). +You can then use an SQL function to convert the type within the statement. +For example: + + INSERT INTO price(code, price) VALUES (?, CONVERT(MONEY,?)) + +The C<CONVERT> function used here is just an example. The actual function +and syntax will vary between different databases and is non-portable. + +See also L</"Placeholders and Bind Values"> for more information. + + +=head3 C<bind_param_inout> + + $rc = $sth->bind_param_inout($p_num, \$bind_value, $max_len) or die $sth->errstr; + $rv = $sth->bind_param_inout($p_num, \$bind_value, $max_len, \%attr) or ... + $rv = $sth->bind_param_inout($p_num, \$bind_value, $max_len, $bind_type) or ... + +This method acts like L</bind_param>, but also enables values to be +updated by the statement. The statement is typically +a call to a stored procedure. The C<$bind_value> must be passed as a +reference to the actual value to be used. + +Note that unlike L</bind_param>, the C<$bind_value> variable is not +copied when C<bind_param_inout> is called. Instead, the value in the +variable is read at the time L</execute> is called. + +The additional C<$max_len> parameter specifies the minimum amount of +memory to allocate to C<$bind_value> for the new value. If the value +returned from the database is too +big to fit, then the execution should fail. If unsure what value to use, +pick a generous length, i.e., a length larger than the longest value that would ever be +returned. The only cost of using a larger value than needed is wasted memory. + +Undefined values or C<undef> are used to indicate null values. +See also L</"Placeholders and Bind Values"> for more information. + + +=head3 C<bind_param_array> + + $rc = $sth->bind_param_array($p_num, $array_ref_or_value) + $rc = $sth->bind_param_array($p_num, $array_ref_or_value, \%attr) + $rc = $sth->bind_param_array($p_num, $array_ref_or_value, $bind_type) + +The C<bind_param_array> method is used to bind an array of values +to a placeholder embedded in the prepared statement which is to be executed +with L</execute_array>. For example: + + $dbh->{RaiseError} = 1; # save having to check each method call + $sth = $dbh->prepare("INSERT INTO staff (first_name, last_name, dept) VALUES(?, ?, ?)"); + $sth->bind_param_array(1, [ 'John', 'Mary', 'Tim' ]); + $sth->bind_param_array(2, [ 'Booth', 'Todd', 'Robinson' ]); + $sth->bind_param_array(3, "SALES"); # scalar will be reused for each row + $sth->execute_array( { ArrayTupleStatus => \my @tuple_status } ); + +The C<%attr> ($bind_type) argument is the same as defined for L</bind_param>. +Refer to L</bind_param> for general details on using placeholders. + +(Note that bind_param_array() can I<not> be used to expand a +placeholder into a list of values for a statement like "SELECT foo +WHERE bar IN (?)". A placeholder can only ever represent one value +per execution.) + +Scalar values, including C<undef>, may also be bound by +C<bind_param_array>. In which case the same value will be used for each +L</execute> call. Driver-specific implementations may behave +differently, e.g., when binding to a stored procedure call, some +databases may permit mixing scalars and arrays as arguments. + +The default implementation provided by DBI (for drivers that have +not implemented array binding) is to iteratively call L</execute> for +each parameter tuple provided in the bound arrays. Drivers may +provide more optimized implementations using whatever bulk operation +support the database API provides. The default driver behaviour should +match the default DBI behaviour, but always consult your driver +documentation as there may be driver specific issues to consider. + +Note that the default implementation currently only supports non-data +returning statements (INSERT, UPDATE, but not SELECT). Also, +C<bind_param_array> and L</bind_param> cannot be mixed in the same +statement execution, and C<bind_param_array> must be used with +L</execute_array>; using C<bind_param_array> will have no effect +for L</execute>. + +The C<bind_param_array> method was added in DBI 1.22. + +=head3 C<execute> + + $rv = $sth->execute or die $sth->errstr; + $rv = $sth->execute(@bind_values) or die $sth->errstr; + +Perform whatever processing is necessary to execute the prepared +statement. An C<undef> is returned if an error occurs. A successful +C<execute> always returns true regardless of the number of rows affected, +even if it's zero (see below). It is always important to check the +return status of C<execute> (and most other DBI methods) for errors +if you're not using L</RaiseError>. + +For a I<non>-C<SELECT> statement, C<execute> returns the number of rows +affected, if known. If no rows were affected, then C<execute> returns +"C<0E0>", which Perl will treat as 0 but will regard as true. Note that it +is I<not> an error for no rows to be affected by a statement. If the +number of rows affected is not known, then C<execute> returns -1. + +For C<SELECT> statements, execute simply "starts" the query within the +database engine. Use one of the fetch methods to retrieve the data after +calling C<execute>. The C<execute> method does I<not> return the number of +rows that will be returned by the query (because most databases can't +tell in advance), it simply returns a true value. + +You can tell if the statement was a C<SELECT> statement by checking if +C<$sth-E<gt>{NUM_OF_FIELDS}> is greater than zero after calling C<execute>. + +If any arguments are given, then C<execute> will effectively call +L</bind_param> for each value before executing the statement. Values +bound in this way are usually treated as C<SQL_VARCHAR> types unless +the driver can determine the correct type (which is rare), or unless +C<bind_param> (or C<bind_param_inout>) has already been used to +specify the type. + +Note that passing C<execute> an empty array is the same as passing no arguments +at all, which will execute the statement with previously bound values. +That's probably not what you want. + +If execute() is called on a statement handle that's still active +($sth->{Active} is true) then it should effectively call finish() +to tidy up the previous execution results before starting this new +execution. + +=head3 C<execute_array> + + $tuples = $sth->execute_array(\%attr) or die $sth->errstr; + $tuples = $sth->execute_array(\%attr, @bind_values) or die $sth->errstr; + + ($tuples, $rows) = $sth->execute_array(\%attr) or die $sth->errstr; + ($tuples, $rows) = $sth->execute_array(\%attr, @bind_values) or die $sth->errstr; + +Execute the prepared statement once for each parameter tuple +(group of values) provided either in the @bind_values, or by prior +calls to L</bind_param_array>, or via a reference passed in \%attr. + +When called in scalar context the execute_array() method returns the +number of tuples executed, or C<undef> if an error occurred. Like +execute(), a successful execute_array() always returns true regardless +of the number of tuples executed, even if it's zero. If there were any +errors the ArrayTupleStatus array can be used to discover which tuples +failed and with what errors. + +When called in list context the execute_array() method returns two scalars; +$tuples is the same as calling execute_array() in scalar context and $rows is +the number of rows affected for each tuple, if available or +-1 if the driver cannot determine this. NOTE, some drivers cannot determine +the number of rows affected per tuple but can provide the number of rows +affected for the batch. +If you are doing an update operation the returned rows affected may not be what +you expect if, for instance, one or more of the tuples affected the same row +multiple times. Some drivers may not yet support list context, in which case +$rows will be undef, or may not be able to provide the number of rows affected +when performing this batch operation, in which case $rows will be -1. + +Bind values for the tuples to be executed may be supplied row-wise +by an C<ArrayTupleFetch> attribute, or else column-wise in the +C<@bind_values> argument, or else column-wise by prior calls to +L</bind_param_array>. + +Where column-wise binding is used (via the C<@bind_values> argument +or calls to bind_param_array()) the maximum number of elements in +any one of the bound value arrays determines the number of tuples +executed. Placeholders with fewer values in their parameter arrays +are treated as if padded with undef (NULL) values. + +If a scalar value is bound, instead of an array reference, it is +treated as a I<variable> length array with all elements having the +same value. It does not influence the number of tuples executed, +so if all bound arrays have zero elements then zero tuples will +be executed. If I<all> bound values are scalars then one tuple +will be executed, making execute_array() act just like execute(). + +The C<ArrayTupleFetch> attribute can be used to specify a reference +to a subroutine that will be called to provide the bind values for +each tuple execution. The subroutine should return an reference to +an array which contains the appropriate number of bind values, or +return an undef if there is no more data to execute. + +As a convenience, the C<ArrayTupleFetch> attribute can also be +used to specify a statement handle. In which case the fetchrow_arrayref() +method will be called on the given statement handle in order to +provide the bind values for each tuple execution. + +The values specified via bind_param_array() or the @bind_values +parameter may be either scalars, or arrayrefs. If any C<@bind_values> +are given, then C<execute_array> will effectively call L</bind_param_array> +for each value before executing the statement. Values bound in +this way are usually treated as C<SQL_VARCHAR> types unless the +driver can determine the correct type (which is rare), or unless +C<bind_param>, C<bind_param_inout>, C<bind_param_array>, or +C<bind_param_inout_array> has already been used to specify the type. +See L</bind_param_array> for details. + +The C<ArrayTupleStatus> attribute can be used to specify a +reference to an array which will receive the execute status of each +executed parameter tuple. Note the C<ArrayTupleStatus> attribute was +mandatory until DBI 1.38. + +For tuples which are successfully executed, the element at the same +ordinal position in the status array is the resulting rowcount (or -1 +if unknown). +If the execution of a tuple causes an error, then the corresponding +status array element will be set to a reference to an array containing +L</err>, L</errstr> and L</state> set by the failed execution. + +If B<any> tuple execution returns an error, C<execute_array> will +return C<undef>. In that case, the application should inspect the +status array to determine which parameter tuples failed. +Some databases may not continue executing tuples beyond the first +failure. In this case the status array will either hold fewer +elements, or the elements beyond the failure will be undef. + +If all parameter tuples are successfully executed, C<execute_array> +returns the number tuples executed. If no tuples were executed, +then execute_array() returns "C<0E0>", just like execute() does, +which Perl will treat as 0 but will regard as true. + +For example: + + $sth = $dbh->prepare("INSERT INTO staff (first_name, last_name) VALUES (?, ?)"); + my $tuples = $sth->execute_array( + { ArrayTupleStatus => \my @tuple_status }, + \@first_names, + \@last_names, + ); + if ($tuples) { + print "Successfully inserted $tuples records\n"; + } + else { + for my $tuple (0..@last_names-1) { + my $status = $tuple_status[$tuple]; + $status = [0, "Skipped"] unless defined $status; + next unless ref $status; + printf "Failed to insert (%s, %s): %s\n", + $first_names[$tuple], $last_names[$tuple], $status->[1]; + } + } + +Support for data returning statements such as SELECT is driver-specific +and subject to change. At present, the default implementation +provided by DBI only supports non-data returning statements. + +Transaction semantics when using array binding are driver and +database specific. If C<AutoCommit> is on, the default DBI +implementation will cause each parameter tuple to be individually +committed (or rolled back in the event of an error). If C<AutoCommit> +is off, the application is responsible for explicitly committing +the entire set of bound parameter tuples. Note that different +drivers and databases may have different behaviours when some +parameter tuples cause failures. In some cases, the driver or +database may automatically rollback the effect of all prior parameter +tuples that succeeded in the transaction; other drivers or databases +may retain the effect of prior successfully executed parameter +tuples. Be sure to check your driver and database for its specific +behaviour. + +Note that, in general, performance will usually be better with +C<AutoCommit> turned off, and using explicit C<commit> after each +C<execute_array> call. + +The C<execute_array> method was added in DBI 1.22, and ArrayTupleFetch +was added in 1.36. + +=head3 C<execute_for_fetch> + + $tuples = $sth->execute_for_fetch($fetch_tuple_sub); + $tuples = $sth->execute_for_fetch($fetch_tuple_sub, \@tuple_status); + + ($tuples, $rows) = $sth->execute_for_fetch($fetch_tuple_sub); + ($tuples, $rows) = $sth->execute_for_fetch($fetch_tuple_sub, \@tuple_status); + +The execute_for_fetch() method is used to perform bulk operations and +although it is most often used via the execute_array() method you can +use it directly. The main difference between execute_array and +execute_for_fetch is the former does column or row-wise binding and +the latter uses row-wise binding. + +The fetch subroutine, referenced by $fetch_tuple_sub, is expected +to return a reference to an array (known as a 'tuple') or undef. + +The execute_for_fetch() method calls $fetch_tuple_sub, without any +parameters, until it returns a false value. Each tuple returned is +used to provide bind values for an $sth->execute(@$tuple) call. + +In scalar context execute_for_fetch() returns C<undef> if there were any +errors and the number of tuples executed otherwise. Like execute() and +execute_array() a zero is returned as "0E0" so execute_for_fetch() is +only false on error. If there were any errors the @tuple_status array +can be used to discover which tuples failed and with what errors. + +When called in list context execute_for_fetch() returns two scalars; +$tuples is the same as calling execute_for_fetch() in scalar context and $rows is +the sum of the number of rows affected for each tuple, if available or -1 +if the driver cannot determine this. +If you are doing an update operation the returned rows affected may not be what +you expect if, for instance, one or more of the tuples affected the same row +multiple times. Some drivers may not yet support list context, in which case +$rows will be undef, or may not be able to provide the number of rows affected +when performing this batch operation, in which case $rows will be -1. + +If \@tuple_status is passed then the execute_for_fetch method uses +it to return status information. The tuple_status array holds one +element per tuple. If the corresponding execute() did not fail then +the element holds the return value from execute(), which is typically +a row count. If the execute() did fail then the element holds a +reference to an array containing ($sth->err, $sth->errstr, $sth->state). + +If the driver detects an error that it knows means no further tuples can be +executed then it may return, with an error status, even though $fetch_tuple_sub +may still have more tuples to be executed. + +Although each tuple returned by $fetch_tuple_sub is effectively used +to call $sth->execute(@$tuple_array_ref) the exact timing may vary. +Drivers are free to accumulate sets of tuples to pass to the +database server in bulk group operations for more efficient execution. +However, the $fetch_tuple_sub is specifically allowed to return +the same array reference each time (which is what fetchrow_arrayref() +usually does). + +For example: + + my $sel = $dbh1->prepare("select foo, bar from table1"); + $sel->execute; + + my $ins = $dbh2->prepare("insert into table2 (foo, bar) values (?,?)"); + my $fetch_tuple_sub = sub { $sel->fetchrow_arrayref }; + + my @tuple_status; + $rc = $ins->execute_for_fetch($fetch_tuple_sub, \@tuple_status); + my @errors = grep { ref $_ } @tuple_status; + +Similarly, if you already have an array containing the data rows +to be processed you'd use a subroutine to shift off and return +each array ref in turn: + + $ins->execute_for_fetch( sub { shift @array_of_arrays }, \@tuple_status); + +The C<execute_for_fetch> method was added in DBI 1.38. + + +=head3 C<fetchrow_arrayref> + + $ary_ref = $sth->fetchrow_arrayref; + $ary_ref = $sth->fetch; # alias + +Fetches the next row of data and returns a reference to an array +holding the field values. Null fields are returned as C<undef> +values in the array. +This is the fastest way to fetch data, particularly if used with +C<$sth-E<gt>bind_columns>. + +If there are no more rows or if an error occurs, then C<fetchrow_arrayref> +returns an C<undef>. You should check C<$sth-E<gt>err> afterwards (or use the +C<RaiseError> attribute) to discover if the C<undef> returned was due to an +error. + +Note that the same array reference is returned for each fetch, so don't +store the reference and then use it after a later fetch. Also, the +elements of the array are also reused for each row, so take care if you +want to take a reference to an element. See also L</bind_columns>. + +=head3 C<fetchrow_array> + + @ary = $sth->fetchrow_array; + +An alternative to C<fetchrow_arrayref>. Fetches the next row of data +and returns it as a list containing the field values. Null fields +are returned as C<undef> values in the list. + +If there are no more rows or if an error occurs, then C<fetchrow_array> +returns an empty list. You should check C<$sth-E<gt>err> afterwards (or use +the C<RaiseError> attribute) to discover if the empty list returned was +due to an error. + +If called in a scalar context for a statement handle that has more +than one column, it is undefined whether the driver will return +the value of the first column or the last. So don't do that. +Also, in a scalar context, an C<undef> is returned if there are no +more rows or if an error occurred. That C<undef> can't be distinguished +from an C<undef> returned because the first field value was NULL. +For these reasons you should exercise some caution if you use +C<fetchrow_array> in a scalar context. + +=head3 C<fetchrow_hashref> + + $hash_ref = $sth->fetchrow_hashref; + $hash_ref = $sth->fetchrow_hashref($name); + +An alternative to C<fetchrow_arrayref>. Fetches the next row of data +and returns it as a reference to a hash containing field name and field +value pairs. Null fields are returned as C<undef> values in the hash. + +If there are no more rows or if an error occurs, then C<fetchrow_hashref> +returns an C<undef>. You should check C<$sth-E<gt>err> afterwards (or use the +C<RaiseError> attribute) to discover if the C<undef> returned was due to an +error. + +The optional C<$name> parameter specifies the name of the statement handle +attribute. For historical reasons it defaults to "C<NAME>", however using +either "C<NAME_lc>" or "C<NAME_uc>" is recommended for portability. + +The keys of the hash are the same names returned by C<$sth-E<gt>{$name}>. If +more than one field has the same name, there will only be one entry in the +returned hash for those fields, so statements like "C<select foo, foo from bar>" +will return only a single key from C<fetchrow_hashref>. In these cases use +column aliases or C<fetchrow_arrayref>. Note that it is the database server +(and not the DBD implementation) which provides the I<name> for fields +containing functions like "C<count(*)>" or "C<max(c_foo)>" and they may clash +with existing column names (most databases don't care about duplicate column +names in a result-set). If you want these to return as unique names that are +the same across databases, use I<aliases>, as in "C<select count(*) as cnt>" +or "C<select max(c_foo) mx_foo, ...>" depending on the syntax your database +supports. + +Because of the extra work C<fetchrow_hashref> and Perl have to perform, it +is not as efficient as C<fetchrow_arrayref> or C<fetchrow_array>. + +By default a reference to a new hash is returned for each row. +It is likely that a future version of the DBI will support an +attribute which will enable the same hash to be reused for each +row. This will give a significant performance boost, but it won't +be enabled by default because of the risk of breaking old code. + + +=head3 C<fetchall_arrayref> + + $tbl_ary_ref = $sth->fetchall_arrayref; + $tbl_ary_ref = $sth->fetchall_arrayref( $slice ); + $tbl_ary_ref = $sth->fetchall_arrayref( $slice, $max_rows ); + +The C<fetchall_arrayref> method can be used to fetch all the data to be +returned from a prepared and executed statement handle. It returns a +reference to an array that contains one reference per row. + +If called on an I<inactive> statement handle, C<fetchall_arrayref> returns undef. + +If there are no rows left to return from an I<active> statement handle, C<fetchall_arrayref> returns a reference +to an empty array. If an error occurs, C<fetchall_arrayref> returns the +data fetched thus far, which may be none. You should check C<$sth-E<gt>err> +afterwards (or use the C<RaiseError> attribute) to discover if the data is +complete or was truncated due to an error. + +If $slice is an array reference, C<fetchall_arrayref> uses L</fetchrow_arrayref> +to fetch each row as an array ref. If the $slice array is not empty +then it is used as a slice to select individual columns by perl array +index number (starting at 0, unlike column and parameter numbers which +start at 1). + +With no parameters, or if $slice is undefined, C<fetchall_arrayref> +acts as if passed an empty array ref. + +For example, to fetch just the first column of every row: + + $tbl_ary_ref = $sth->fetchall_arrayref([0]); + +To fetch the second to last and last column of every row: + + $tbl_ary_ref = $sth->fetchall_arrayref([-2,-1]); + +Those two examples both return a reference to an array of array refs. + +If $slice is a hash reference, C<fetchall_arrayref> fetches each row as a hash +reference. If the $slice hash is empty then the keys in the hashes have +whatever name lettercase is returned by default. (See L</FetchHashKeyName> +attribute.) If the $slice hash is I<not> empty, then it is used as a slice to +select individual columns by name. The values of the hash should be set to 1. +The key names of the returned hashes match the letter case of the names in the +parameter hash, regardless of the L</FetchHashKeyName> attribute. + +For example, to fetch all fields of every row as a hash ref: + + $tbl_ary_ref = $sth->fetchall_arrayref({}); + +To fetch only the fields called "foo" and "bar" of every row as a hash ref +(with keys named "foo" and "BAR", regardless of the original capitalization): + + $tbl_ary_ref = $sth->fetchall_arrayref({ foo=>1, BAR=>1 }); + +Those two examples both return a reference to an array of hash refs. + +If $slice is a I<reference to a hash reference>, that hash is used to select +and rename columns. The keys are 0-based column index numbers and the values +are the corresponding keys for the returned row hashes. + +For example, to fetch only the first and second columns of every row as a hash +ref (with keys named "k" and "v" regardless of their original names): + + $tbl_ary_ref = $sth->fetchall_arrayref( \{ 0 => 'k', 1 => 'v' } ); + +If $max_rows is defined and greater than or equal to zero then it +is used to limit the number of rows fetched before returning. +fetchall_arrayref() can then be called again to fetch more rows. +This is especially useful when you need the better performance of +fetchall_arrayref() but don't have enough memory to fetch and return +all the rows in one go. + +Here's an example (assumes RaiseError is enabled): + + my $rows = []; # cache for batches of rows + while( my $row = ( shift(@$rows) || # get row from cache, or reload cache: + shift(@{$rows=$sth->fetchall_arrayref(undef,10_000)||[]}) ) + ) { + ... + } + +That I<might> be the fastest way to fetch and process lots of rows using the DBI, +but it depends on the relative cost of method calls vs memory allocation. + +A standard C<while> loop with column binding is often faster because +the cost of allocating memory for the batch of rows is greater than +the saving by reducing method calls. It's possible that the DBI may +provide a way to reuse the memory of a previous batch in future, which +would then shift the balance back towards fetchall_arrayref(). + + +=head3 C<fetchall_hashref> + + $hash_ref = $sth->fetchall_hashref($key_field); + +The C<fetchall_hashref> method can be used to fetch all the data to be +returned from a prepared and executed statement handle. It returns a reference +to a hash containing a key for each distinct value of the $key_field column +that was fetched. For each key the corresponding value is a reference to a hash +containing all the selected columns and their values, as returned by +C<fetchrow_hashref()>. + +If there are no rows to return, C<fetchall_hashref> returns a reference +to an empty hash. If an error occurs, C<fetchall_hashref> returns the +data fetched thus far, which may be none. You should check +C<$sth-E<gt>err> afterwards (or use the C<RaiseError> attribute) to +discover if the data is complete or was truncated due to an error. + +The $key_field parameter provides the name of the field that holds the +value to be used for the key for the returned hash. For example: + + $dbh->{FetchHashKeyName} = 'NAME_lc'; + $sth = $dbh->prepare("SELECT FOO, BAR, ID, NAME, BAZ FROM TABLE"); + $sth->execute; + $hash_ref = $sth->fetchall_hashref('id'); + print "Name for id 42 is $hash_ref->{42}->{name}\n"; + +The $key_field parameter can also be specified as an integer column +number (counting from 1). If $key_field doesn't match any column in +the statement, as a name first then as a number, then an error is +returned. + +For queries returning more than one 'key' column, you can specify +multiple column names by passing $key_field as a reference to an +array containing one or more key column names (or index numbers). +For example: + + $sth = $dbh->prepare("SELECT foo, bar, baz FROM table"); + $sth->execute; + $hash_ref = $sth->fetchall_hashref( [ qw(foo bar) ] ); + print "For foo 42 and bar 38, baz is $hash_ref->{42}->{38}->{baz}\n"; + +The fetchall_hashref() method is normally used only where the key +fields values for each row are unique. If multiple rows are returned +with the same values for the key fields then later rows overwrite +earlier ones. + +=head3 C<finish> + + $rc = $sth->finish; + +Indicate that no more data will be fetched from this statement handle +before it is either executed again or destroyed. You almost certainly +do I<not> need to call this method. + +Adding calls to C<finish> after loop that fetches all rows is a common mistake, +don't do it, it can mask genuine problems like uncaught fetch errors. + +When all the data has been fetched from a C<SELECT> statement, the driver will +automatically call C<finish> for you. So you should I<not> call it explicitly +I<except> when you know that you've not fetched all the data from a statement +handle I<and> the handle won't be destroyed soon. + +The most common example is when you only want to fetch just one row, +but in that case the C<selectrow_*> methods are usually better anyway. + +Consider a query like: + + SELECT foo FROM table WHERE bar=? ORDER BY baz + +on a very large table. When executed, the database server will have to use +temporary buffer space to store the sorted rows. If, after executing +the handle and selecting just a few rows, the handle won't be re-executed for +some time and won't be destroyed, the C<finish> method can be used to tell +the server that the buffer space can be freed. + +Calling C<finish> resets the L</Active> attribute for the statement. It +may also make some statement handle attributes (such as C<NAME> and C<TYPE>) +unavailable if they have not already been accessed (and thus cached). + +The C<finish> method does not affect the transaction status of the +database connection. It has nothing to do with transactions. It's mostly an +internal "housekeeping" method that is rarely needed. +See also L</disconnect> and the L</Active> attribute. + +The C<finish> method should have been called C<discard_pending_rows>. + + +=head3 C<rows> + + $rv = $sth->rows; + +Returns the number of rows affected by the last row affecting command, +or -1 if the number of rows is not known or not available. + +Generally, you can only rely on a row count after a I<non>-C<SELECT> +C<execute> (for some specific operations like C<UPDATE> and C<DELETE>), or +after fetching all the rows of a C<SELECT> statement. + +For C<SELECT> statements, it is generally not possible to know how many +rows will be returned except by fetching them all. Some drivers will +return the number of rows the application has fetched so far, but +others may return -1 until all rows have been fetched. So use of the +C<rows> method or C<$DBI::rows> with C<SELECT> statements is not +recommended. + +One alternative method to get a row count for a C<SELECT> is to execute a +"SELECT COUNT(*) FROM ..." SQL statement with the same "..." as your +query and then fetch the row count from that. + + +=head3 C<bind_col> + + $rc = $sth->bind_col($column_number, \$var_to_bind); + $rc = $sth->bind_col($column_number, \$var_to_bind, \%attr ); + $rc = $sth->bind_col($column_number, \$var_to_bind, $bind_type ); + +Binds a Perl variable and/or some attributes to an output column +(field) of a C<SELECT> statement. Column numbers count up from 1. +You do not need to bind output columns in order to fetch data. +For maximum portability between drivers, bind_col() should be called +after execute() and not before. +See also L</bind_columns> for an example. + +The binding is performed at a low level using Perl aliasing. +Whenever a row is fetched from the database $var_to_bind appears +to be automatically updated simply because it now refers to the same +memory location as the corresponding column value. This makes using +bound variables very efficient. +Binding a tied variable doesn't work, currently. + +The L</bind_param> method +performs a similar, but opposite, function for input variables. + +B<Data Types for Column Binding> + +The C<\%attr> parameter can be used to hint at the data type +formatting the column should have. For example, you can use: + + $sth->bind_col(1, undef, { TYPE => SQL_DATETIME }); + +to specify that you'd like the column (which presumably is some +kind of datetime type) to be returned in the standard format for +SQL_DATETIME, which is 'YYYY-MM-DD HH:MM:SS', rather than the +native formatting the database would normally use. + +There's no $var_to_bind in that example to emphasize the point +that bind_col() works on the underlying column and not just +a particular bound variable. + +As a short-cut for the common case, the data type can be passed +directly, in place of the C<\%attr> hash reference. This example is +equivalent to the one above: + + $sth->bind_col(1, undef, SQL_DATETIME); + +The C<TYPE> value indicates the standard (non-driver-specific) type for +this parameter. To specify the driver-specific type, the driver may +support a driver-specific attribute, such as C<{ ora_type =E<gt> 97 }>. + +The SQL_DATETIME and other related constants can be imported using + + use DBI qw(:sql_types); + +See L</"DBI Constants"> for more information. + +Few drivers support specifying a data type via a C<bind_col> call +(most will simply ignore the data type). Fewer still allow the data +type to be altered once set. + +The TYPE attribute for bind_col() was first specified in DBI 1.41. + +From DBI 1.611, drivers can use the C<TYPE> attribute to attempt to +cast the bound scalar to a perl type which more closely matches +C<TYPE>. At present DBI supports C<SQL_INTEGER>, C<SQL_DOUBLE> and +C<SQL_NUMERIC>. See L</sql_type_cast> for details of how types are +cast. + +B<Other attributes for Column Binding> + +The C<\%attr> parameter may also contain the following attributes: + +=over + +=item C<StrictlyTyped> + +If a C<TYPE> attribute is passed to bind_col, then the driver will +attempt to change the bound perl scalar to match the type more +closely. If the bound value cannot be cast to the requested C<TYPE> +then by default it is left untouched and no error is generated. If you +specify C<StrictlyTyped> as 1 and the cast fails, this will generate +an error. + +This attribute was first added in DBI 1.611. When 1.611 was released +few drivers actually supported this attribute but DBD::Oracle and +DBD::ODBC should from versions 1.24. + +=item C<DiscardString> + +When the C<TYPE> attribute is passed to L</bind_col> and the driver +successfully casts the bound perl scalar to a non-string type +then if C<DiscardString> is set to 1, the string portion of the +scalar will be discarded. By default, C<DiscardString> is not set. + +This attribute was first added in DBI 1.611. When 1.611 was released +few drivers actually supported this attribute but DBD::Oracle and +DBD::ODBC should from versions 1.24. + +=back + + +=head3 C<bind_columns> + + $rc = $sth->bind_columns(@list_of_refs_to_vars_to_bind); + +Calls L</bind_col> for each column of the C<SELECT> statement. + +The list of references should have the same number of elements as the number of +columns in the C<SELECT> statement. If it doesn't then C<bind_columns> will +bind the elements given, up to the number of columns, and then return an error. + +For maximum portability between drivers, bind_columns() should be called +after execute() and not before. + +For example: + + $dbh->{RaiseError} = 1; # do this, or check every call for errors + $sth = $dbh->prepare(q{ SELECT region, sales FROM sales_by_region }); + $sth->execute; + my ($region, $sales); + + # Bind Perl variables to columns: + $rv = $sth->bind_columns(\$region, \$sales); + + # you can also use Perl's \(...) syntax (see perlref docs): + # $sth->bind_columns(\($region, $sales)); + + # Column binding is the most efficient way to fetch data + while ($sth->fetch) { + print "$region: $sales\n"; + } + +For compatibility with old scripts, the first parameter will be +ignored if it is C<undef> or a hash reference. + +Here's a more fancy example that binds columns to the values I<inside> +a hash (thanks to H.Merijn Brand): + + $sth->execute; + my %row; + $sth->bind_columns( \( @row{ @{$sth->{NAME_lc} } } )); + while ($sth->fetch) { + print "$row{region}: $row{sales}\n"; + } + + +=head3 C<dump_results> + + $rows = $sth->dump_results($maxlen, $lsep, $fsep, $fh); + +Fetches all the rows from C<$sth>, calls C<DBI::neat_list> for each row, and +prints the results to C<$fh> (defaults to C<STDOUT>) separated by C<$lsep> +(default C<"\n">). C<$fsep> defaults to C<", "> and C<$maxlen> defaults to 35. + +This method is designed as a handy utility for prototyping and +testing queries. Since it uses L</neat_list> to +format and edit the string for reading by humans, it is not recommended +for data transfer applications. + + +=head2 Statement Handle Attributes + +This section describes attributes specific to statement handles. Most +of these attributes are read-only. + +Changes to these statement handle attributes do not affect any other +existing or future statement handles. + +Attempting to set or get the value of an unknown attribute generates a warning, +except for private driver specific attributes (which all have names +starting with a lowercase letter). + +Example: + + ... = $h->{NUM_OF_FIELDS}; # get/read + +Some drivers cannot provide valid values for some or all of these +attributes until after C<$sth-E<gt>execute> has been successfully +called. Typically the attribute will be C<undef> in these situations. + +Some attributes, like NAME, are not appropriate to some types of +statement, like SELECT. Typically the attribute will be C<undef> +in these situations. + +For drivers which support stored procedures and multiple result sets +(see L</more_results>) these attributes relate to the I<current> result set. + +See also L</finish> to learn more about the effect it +may have on some attributes. + +=head3 C<NUM_OF_FIELDS> + +Type: integer, read-only + +Number of fields (columns) in the data the prepared statement may return. +Statements that don't return rows of data, like C<DELETE> and C<CREATE> +set C<NUM_OF_FIELDS> to 0 (though it may be undef in some drivers). + + +=head3 C<NUM_OF_PARAMS> + +Type: integer, read-only + +The number of parameters (placeholders) in the prepared statement. +See SUBSTITUTION VARIABLES below for more details. + + +=head3 C<NAME> + +Type: array-ref, read-only + +Returns a reference to an array of field names for each column. The +names may contain spaces but should not be truncated or have any +trailing space. Note that the names have the letter case (upper, lower +or mixed) as returned by the driver being used. Portable applications +should use L</NAME_lc> or L</NAME_uc>. + + print "First column name: $sth->{NAME}->[0]\n"; + +Also note that the name returned for (aggregate) functions like C<count(*)> +or C<max(c_foo)> is determined by the database server and not by C<DBI> or +the C<DBD> backend. + +=head3 C<NAME_lc> + +Type: array-ref, read-only + +Like L</NAME> but always returns lowercase names. + +=head3 C<NAME_uc> + +Type: array-ref, read-only + +Like L</NAME> but always returns uppercase names. + +=head3 C<NAME_hash> + +Type: hash-ref, read-only + +=head3 C<NAME_lc_hash> + +Type: hash-ref, read-only + +=head3 C<NAME_uc_hash> + +Type: hash-ref, read-only + +The C<NAME_hash>, C<NAME_lc_hash>, and C<NAME_uc_hash> attributes +return column name information as a reference to a hash. + +The keys of the hash are the names of the columns. The letter case of +the keys corresponds to the letter case returned by the C<NAME>, +C<NAME_lc>, and C<NAME_uc> attributes respectively (as described above). + +The value of each hash entry is the perl index number of the +corresponding column (counting from 0). For example: + + $sth = $dbh->prepare("select Id, Name from table"); + $sth->execute; + @row = $sth->fetchrow_array; + print "Name $row[ $sth->{NAME_lc_hash}{name} ]\n"; + + +=head3 C<TYPE> + +Type: array-ref, read-only + +Returns a reference to an array of integer values for each +column. The value indicates the data type of the corresponding column. + +The values correspond to the international standards (ANSI X3.135 +and ISO/IEC 9075) which, in general terms, means ODBC. Driver-specific +types that don't exactly match standard types should generally return +the same values as an ODBC driver supplied by the makers of the +database. That might include private type numbers in ranges the vendor +has officially registered with the ISO working group: + + ftp://sqlstandards.org/SC32/SQL_Registry/ + +Where there's no vendor-supplied ODBC driver to be compatible with, +the DBI driver can use type numbers in the range that is now +officially reserved for use by the DBI: -9999 to -9000. + +All possible values for C<TYPE> should have at least one entry in the +output of the C<type_info_all> method (see L</type_info_all>). + +=head3 C<PRECISION> + +Type: array-ref, read-only + +Returns a reference to an array of integer values for each column. + +For numeric columns, the value is the maximum number of digits +(without considering a sign character or decimal point). Note that +the "display size" for floating point types (REAL, FLOAT, DOUBLE) +can be up to 7 characters greater than the precision (for the +sign + decimal point + the letter E + a sign + 2 or 3 digits). + +For any character type column the value is the OCTET_LENGTH, +in other words the number of bytes, not characters. + +(More recent standards refer to this as COLUMN_SIZE but we stick +with PRECISION for backwards compatibility.) + +=head3 C<SCALE> + +Type: array-ref, read-only + +Returns a reference to an array of integer values for each column. +NULL (C<undef>) values indicate columns where scale is not applicable. + +=head3 C<NULLABLE> + +Type: array-ref, read-only + +Returns a reference to an array indicating the possibility of each +column returning a null. Possible values are C<0> +(or an empty string) = no, C<1> = yes, C<2> = unknown. + + print "First column may return NULL\n" if $sth->{NULLABLE}->[0]; + + +=head3 C<CursorName> + +Type: string, read-only + +Returns the name of the cursor associated with the statement handle, if +available. If not available or if the database driver does not support the +C<"where current of ..."> SQL syntax, then it returns C<undef>. + + +=head3 C<Database> + +Type: dbh, read-only + +Returns the parent $dbh of the statement handle. + + +=head3 C<Statement> + +Type: string, read-only + +Returns the statement string passed to the L</prepare> method. + + +=head3 C<ParamValues> + +Type: hash ref, read-only + +Returns a reference to a hash containing the values currently bound +to placeholders. The keys of the hash are the 'names' of the +placeholders, typically integers starting at 1. Returns undef if +not supported by the driver. + +See L</ShowErrorStatement> for an example of how this is used. + +* Keys: + +If the driver supports C<ParamValues> but no values have been bound +yet then the driver should return a hash with placeholders names +in the keys but all the values undef, but some drivers may return +a ref to an empty hash because they can't pre-determine the names. + +It is possible that the keys in the hash returned by C<ParamValues> +are not exactly the same as those implied by the prepared statement. +For example, DBD::Oracle translates 'C<?>' placeholders into 'C<:pN>' +where N is a sequence number starting at 1. + +* Values: + +It is possible that the values in the hash returned by C<ParamValues> +are not I<exactly> the same as those passed to bind_param() or execute(). +The driver may have slightly modified values in some way based on the +TYPE the value was bound with. For example a floating point value +bound as an SQL_INTEGER type may be returned as an integer. +The values returned by C<ParamValues> can be passed to another +bind_param() method with the same TYPE and will be seen by the +database as the same value. See also L</ParamTypes> below. + +The C<ParamValues> attribute was added in DBI 1.28. + +=head3 C<ParamTypes> + +Type: hash ref, read-only + +Returns a reference to a hash containing the type information +currently bound to placeholders. +Returns undef if not supported by the driver. + +* Keys: + +See L</ParamValues> above. + +* Values: + +The hash values are hashrefs of type information in the same form as that +passed to the various bind_param() methods (See L</bind_param> for the format +and values). + +It is possible that the values in the hash returned by C<ParamTypes> +are not exactly the same as those passed to bind_param() or execute(). +Param attributes specified using the abbreviated form, like this: + + $sth->bind_param(1, SQL_INTEGER); + +are returned in the expanded form, as if called like this: + + $sth->bind_param(1, { TYPE => SQL_INTEGER }); + +The driver may have modified the type information in some way based +on the bound values, other hints provided by the prepare()'d +SQL statement, or alternate type mappings required by the driver or target +database system. The driver may also add private keys (with names beginning +with the drivers reserved prefix, e.g., odbc_xxx). + +* Example: + +The keys and values in the returned hash can be passed to the various +bind_param() methods to effectively reproduce a previous param binding. +For example: + + # assuming $sth1 is a previously prepared statement handle + my $sth2 = $dbh->prepare( $sth1->{Statement} ); + my $ParamValues = $sth1->{ParamValues} || {}; + my $ParamTypes = $sth1->{ParamTypes} || {}; + $sth2->bind_param($_, $ParamValues->{$_} $ParamTypes->{$_}) + for keys %{ {%$ParamValues, %$ParamTypes} }; + $sth2->execute(); + +The C<ParamTypes> attribute was added in DBI 1.49. Implementation +is the responsibility of individual drivers; the DBI layer default +implementation simply returns undef. + + +=head3 C<ParamArrays> + +Type: hash ref, read-only + +Returns a reference to a hash containing the values currently bound to +placeholders with L</execute_array> or L</bind_param_array>. The +keys of the hash are the 'names' of the placeholders, typically +integers starting at 1. Returns undef if not supported by the driver +or no arrays of parameters are bound. + +Each key value is an array reference containing a list of the bound +parameters for that column. + +For example: + + $sth = $dbh->prepare("INSERT INTO staff (id, name) values (?,?)"); + $sth->execute_array({},[1,2], ['fred','dave']); + if ($sth->{ParamArrays}) { + foreach $param (keys %{$sth->{ParamArrays}}) { + printf "Parameters for %s : %s\n", $param, + join(",", @{$sth->{ParamArrays}->{$param}}); + } + } + +It is possible that the values in the hash returned by C<ParamArrays> +are not I<exactly> the same as those passed to L</bind_param_array> or +L</execute_array>. The driver may have slightly modified values in some +way based on the TYPE the value was bound with. For example a floating +point value bound as an SQL_INTEGER type may be returned as an +integer. + +It is also possible that the keys in the hash returned by +C<ParamArrays> are not exactly the same as those implied by the +prepared statement. For example, DBD::Oracle translates 'C<?>' +placeholders into 'C<:pN>' where N is a sequence number starting at 1. + +=head3 C<RowsInCache> + +Type: integer, read-only + +If the driver supports a local row cache for C<SELECT> statements, then +this attribute holds the number of un-fetched rows in the cache. If the +driver doesn't, then it returns C<undef>. Note that some drivers pre-fetch +rows on execute, whereas others wait till the first fetch. + +See also the L</RowCacheSize> database handle attribute. + +=head1 FURTHER INFORMATION + +=head2 Catalog Methods + +An application can retrieve metadata information from the DBMS by issuing +appropriate queries on the views of the Information Schema. Unfortunately, +C<INFORMATION_SCHEMA> views are seldom supported by the DBMS. +Special methods (catalog methods) are available to return result sets +for a small but important portion of that metadata: + + column_info + foreign_key_info + primary_key_info + table_info + statistics_info + +All catalog methods accept arguments in order to restrict the result sets. +Passing C<undef> to an optional argument does not constrain the search for +that argument. +However, an empty string ('') is treated as a regular search criteria +and will only match an empty value. + +B<Note>: SQL/CLI and ODBC differ in the handling of empty strings. An +empty string will not restrict the result set in SQL/CLI. + +Most arguments in the catalog methods accept only I<ordinary values>, e.g. +the arguments of C<primary_key_info()>. +Such arguments are treated as a literal string, i.e. the case is significant +and quote characters are taken literally. + +Some arguments in the catalog methods accept I<search patterns> (strings +containing '_' and/or '%'), e.g. the C<$table> argument of C<column_info()>. +Passing '%' is equivalent to leaving the argument C<undef>. + +B<Caveat>: The underscore ('_') is valid and often used in SQL identifiers. +Passing such a value to a search pattern argument may return more rows than +expected! +To include pattern characters as literals, they must be preceded by an +escape character which can be achieved with + + $esc = $dbh->get_info( 14 ); # SQL_SEARCH_PATTERN_ESCAPE + $search_pattern =~ s/([_%])/$esc$1/g; + +The ODBC and SQL/CLI specifications define a way to change the default +behaviour described above: All arguments (except I<list value arguments>) +are treated as I<identifier> if the C<SQL_ATTR_METADATA_ID> attribute is +set to C<SQL_TRUE>. +I<Quoted identifiers> are very similar to I<ordinary values>, i.e. their +body (the string within the quotes) is interpreted literally. +I<Unquoted identifiers> are compared in UPPERCASE. + +The DBI (currently) does not support the C<SQL_ATTR_METADATA_ID> attribute, +i.e. it behaves like an ODBC driver where C<SQL_ATTR_METADATA_ID> is set to +C<SQL_FALSE>. + + +=head2 Transactions + +Transactions are a fundamental part of any robust database system. They +protect against errors and database corruption by ensuring that sets of +related changes to the database take place in atomic (indivisible, +all-or-nothing) units. + +This section applies to databases that support transactions and where +C<AutoCommit> is off. See L</AutoCommit> for details of using C<AutoCommit> +with various types of databases. + +The recommended way to implement robust transactions in Perl +applications is to use C<RaiseError> and S<C<eval { ... }>> +(which is very fast, unlike S<C<eval "...">>). For example: + + $dbh->{AutoCommit} = 0; # enable transactions, if possible + $dbh->{RaiseError} = 1; + eval { + foo(...) # do lots of work here + bar(...) # including inserts + baz(...) # and updates + $dbh->commit; # commit the changes if we get this far + }; + if ($@) { + warn "Transaction aborted because $@"; + # now rollback to undo the incomplete changes + # but do it in an eval{} as it may also fail + eval { $dbh->rollback }; + # add other application on-error-clean-up code here + } + +If the C<RaiseError> attribute is not set, then DBI calls would need to be +manually checked for errors, typically like this: + + $h->method(@args) or die $h->errstr; + +With C<RaiseError> set, the DBI will automatically C<die> if any DBI method +call on that handle (or a child handle) fails, so you don't have to +test the return value of each method call. See L</RaiseError> for more +details. + +A major advantage of the C<eval> approach is that the transaction will be +properly rolled back if I<any> code (not just DBI calls) in the inner +application dies for any reason. The major advantage of using the +C<$h-E<gt>{RaiseError}> attribute is that all DBI calls will be checked +automatically. Both techniques are strongly recommended. + +After calling C<commit> or C<rollback> many drivers will not let you +fetch from a previously active C<SELECT> statement handle that's a child +of the same database handle. A typical way round this is to connect the +the database twice and use one connection for C<SELECT> statements. + +See L</AutoCommit> and L</disconnect> for other important information +about transactions. + + +=head2 Handling BLOB / LONG / Memo Fields + +Many databases support "blob" (binary large objects), "long", or similar +datatypes for holding very long strings or large amounts of binary +data in a single field. Some databases support variable length long +values over 2,000,000,000 bytes in length. + +Since values of that size can't usually be held in memory, and because +databases can't usually know in advance the length of the longest long +that will be returned from a C<SELECT> statement (unlike other data +types), some special handling is required. + +In this situation, the value of the C<$h-E<gt>{LongReadLen}> +attribute is used to determine how much buffer space to allocate +when fetching such fields. The C<$h-E<gt>{LongTruncOk}> attribute +is used to determine how to behave if a fetched value can't fit +into the buffer. + +See the description of L</LongReadLen> for more information. + +When trying to insert long or binary values, placeholders should be used +since there are often limits on the maximum size of an C<INSERT> +statement and the L</quote> method generally can't cope with binary +data. See L</Placeholders and Bind Values>. + + +=head2 Simple Examples + +Here's a complete example program to select and fetch some data: + + my $data_source = "dbi::DriverName:db_name"; + my $dbh = DBI->connect($data_source, $user, $password) + or die "Can't connect to $data_source: $DBI::errstr"; + + my $sth = $dbh->prepare( q{ + SELECT name, phone + FROM mytelbook + }) or die "Can't prepare statement: $DBI::errstr"; + + my $rc = $sth->execute + or die "Can't execute statement: $DBI::errstr"; + + print "Query will return $sth->{NUM_OF_FIELDS} fields.\n\n"; + print "Field names: @{ $sth->{NAME} }\n"; + + while (($name, $phone) = $sth->fetchrow_array) { + print "$name: $phone\n"; + } + # check for problems which may have terminated the fetch early + die $sth->errstr if $sth->err; + + $dbh->disconnect; + +Here's a complete example program to insert some data from a file. +(This example uses C<RaiseError> to avoid needing to check each call). + + my $dbh = DBI->connect("dbi:DriverName:db_name", $user, $password, { + RaiseError => 1, AutoCommit => 0 + }); + + my $sth = $dbh->prepare( q{ + INSERT INTO table (name, phone) VALUES (?, ?) + }); + + open FH, "<phone.csv" or die "Unable to open phone.csv: $!"; + while (<FH>) { + chomp; + my ($name, $phone) = split /,/; + $sth->execute($name, $phone); + } + close FH; + + $dbh->commit; + $dbh->disconnect; + +Here's how to convert fetched NULLs (undefined values) into empty strings: + + while($row = $sth->fetchrow_arrayref) { + # this is a fast and simple way to deal with nulls: + foreach (@$row) { $_ = '' unless defined } + print "@$row\n"; + } + +The C<q{...}> style quoting used in these examples avoids clashing with +quotes that may be used in the SQL statement. Use the double-quote like +C<qq{...}> operator if you want to interpolate variables into the string. +See L<perlop/"Quote and Quote-like Operators"> for more details. + +=head2 Threads and Thread Safety + +Perl 5.7 and later support a new threading model called iThreads. +(The old "5.005 style" threads are not supported by the DBI.) + +In the iThreads model each thread has it's own copy of the perl +interpreter. When a new thread is created the original perl +interpreter is 'cloned' to create a new copy for the new thread. + +If the DBI and drivers are loaded and handles created before the +thread is created then it will get a cloned copy of the DBI, the +drivers and the handles. + +However, the internal pointer data within the handles will refer +to the DBI and drivers in the original interpreter. Using those +handles in the new interpreter thread is not safe, so the DBI detects +this and croaks on any method call using handles that don't belong +to the current thread (except for DESTROY). + +Because of this (possibly temporary) restriction, newly created +threads must make their own connections to the database. Handles +can't be shared across threads. + +But BEWARE, some underlying database APIs (the code the DBD driver +uses to talk to the database, often supplied by the database vendor) +are not thread safe. If it's not thread safe, then allowing more +than one thread to enter the code at the same time may cause +subtle/serious problems. In some cases allowing more than +one thread to enter the code, even if I<not> at the same time, +can cause problems. You have been warned. + +Using DBI with perl threads is not yet recommended for production +environments. For more information see +L<http://www.perlmonks.org/index.pl?node_id=288022> + +Note: There is a bug in perl 5.8.2 when configured with threads +and debugging enabled (bug #24463) which causes a DBI test to fail. + +=head2 Signal Handling and Canceling Operations + +[The following only applies to systems with unix-like signal handling. +I'd welcome additions for other systems, especially Windows.] + +The first thing to say is that signal handling in Perl versions less +than 5.8 is I<not> safe. There is always a small risk of Perl +crashing and/or core dumping when, or after, handling a signal +because the signal could arrive and be handled while internal data +structures are being changed. If the signal handling code +used those same internal data structures it could cause all manner +of subtle and not-so-subtle problems. The risk was reduced with +5.4.4 but was still present in all perls up through 5.8.0. + +Beginning in perl 5.8.0 perl implements 'safe' signal handling if +your system has the POSIX sigaction() routine. Now when a signal +is delivered perl just makes a note of it but does I<not> run the +%SIG handler. The handling is 'deferred' until a 'safe' moment. + +Although this change made signal handling safe, it also lead to +a problem with signals being deferred for longer than you'd like. +If a signal arrived while executing a system call, such as waiting +for data on a network connection, the signal is noted and then the +system call that was executing returns with an EINTR error code +to indicate that it was interrupted. All fine so far. + +The problem comes when the code that made the system call sees the +EINTR code and decides it's going to call it again. Perl doesn't +do that, but database code sometimes does. If that happens then the +signal handler doesn't get called until later. Maybe much later. + +Fortunately there are ways around this which we'll discuss below. +Unfortunately they make signals unsafe again. + +The two most common uses of signals in relation to the DBI are for +canceling operations when the user types Ctrl-C (interrupt), and for +implementing a timeout using C<alarm()> and C<$SIG{ALRM}>. + +=over 4 + +=item Cancel + +The DBI provides a C<cancel> method for statement handles. The +C<cancel> method should abort the current operation and is designed +to be called from a signal handler. For example: + + $SIG{INT} = sub { $sth->cancel }; + +However, few drivers implement this (the DBI provides a default +method that just returns C<undef>) and, even if implemented, there +is still a possibility that the statement handle, and even the +parent database handle, will not be usable afterwards. + +If C<cancel> returns true, then it has successfully +invoked the database engine's own cancel function. If it returns false, +then C<cancel> failed. If it returns C<undef>, then the database +driver does not have cancel implemented - very few do. + +=item Timeout + +The traditional way to implement a timeout is to set C<$SIG{ALRM}> +to refer to some code that will be executed when an ALRM signal +arrives and then to call alarm($seconds) to schedule an ALRM signal +to be delivered $seconds in the future. For example: + + eval { + local $SIG{ALRM} = sub { die "TIMEOUT\n" }; # N.B. \n required + eval { + alarm($seconds); + ... code to execute with timeout here (which may die) ... + }; + # outer eval catches alarm that might fire JUST before this alarm(0) + alarm(0); # cancel alarm (if code ran fast) + die "$@" if $@; + }; + if ( $@ eq "TIMEOUT\n" ) { ... } + elsif ($@) { ... } # some other error + +The first (outer) eval is used to avoid the unlikely but possible +chance that the "code to execute" dies and the alarm fires before it +is cancelled. Without the outer eval, if this happened your program +will die if you have no ALRM handler or a non-local alarm handler +will be called. + +Unfortunately, as described above, this won't always work as expected, +depending on your perl version and the underlying database code. + +With Oracle for instance (DBD::Oracle), if the system which hosts +the database is down the DBI->connect() call will hang for several +minutes before returning an error. + +=back + +The solution on these systems is to use the C<POSIX::sigaction()> +routine to gain low level access to how the signal handler is installed. + +The code would look something like this (for the DBD-Oracle connect()): + + use POSIX qw(:signal_h); + + my $mask = POSIX::SigSet->new( SIGALRM ); # signals to mask in the handler + my $action = POSIX::SigAction->new( + sub { die "connect timeout\n" }, # the handler code ref + $mask, + # not using (perl 5.8.2 and later) 'safe' switch or sa_flags + ); + my $oldaction = POSIX::SigAction->new(); + sigaction( SIGALRM, $action, $oldaction ); + my $dbh; + eval { + eval { + alarm(5); # seconds before time out + $dbh = DBI->connect("dbi:Oracle:$dsn" ... ); + }; + alarm(0); # cancel alarm (if connect worked fast) + die "$@\n" if $@; # connect died + }; + sigaction( SIGALRM, $oldaction ); # restore original signal handler + if ( $@ ) { + if ($@ eq "connect timeout\n") {...} + else { # connect died } + } + +See previous example for the reasoning around the double eval. + +Similar techniques can be used for canceling statement execution. + +Unfortunately, this solution is somewhat messy, and it does I<not> work with +perl versions less than perl 5.8 where C<POSIX::sigaction()> appears to be broken. + +For a cleaner implementation that works across perl versions, see Lincoln Baxter's +Sys::SigAction module at L<http://search.cpan.org/~lbaxter/Sys-SigAction/>. +The documentation for Sys::SigAction includes an longer discussion +of this problem, and a DBD::Oracle test script. + +Be sure to read all the signal handling sections of the L<perlipc> manual. + +And finally, two more points to keep firmly in mind. Firstly, +remember that what we've done here is essentially revert to old +style I<unsafe> handling of these signals. So do as little as +possible in the handler. Ideally just die(). Secondly, the handles +in use at the time the signal is handled may not be safe to use +afterwards. + + +=head2 Subclassing the DBI + +DBI can be subclassed and extended just like any other object +oriented module. Before we talk about how to do that, it's important +to be clear about the various DBI classes and how they work together. + +By default C<$dbh = DBI-E<gt>connect(...)> returns a $dbh blessed +into the C<DBI::db> class. And the C<$dbh-E<gt>prepare> method +returns an $sth blessed into the C<DBI::st> class (actually it +simply changes the last four characters of the calling handle class +to be C<::st>). + +The leading 'C<DBI>' is known as the 'root class' and the extra +'C<::db>' or 'C<::st>' are the 'handle type suffixes'. If you want +to subclass the DBI you'll need to put your overriding methods into +the appropriate classes. For example, if you want to use a root class +of C<MySubDBI> and override the do(), prepare() and execute() methods, +then your do() and prepare() methods should be in the C<MySubDBI::db> +class and the execute() method should be in the C<MySubDBI::st> class. + +To setup the inheritance hierarchy the @ISA variable in C<MySubDBI::db> +should include C<DBI::db> and the @ISA variable in C<MySubDBI::st> +should include C<DBI::st>. The C<MySubDBI> root class itself isn't +currently used for anything visible and so, apart from setting @ISA +to include C<DBI>, it can be left empty. + +So, having put your overriding methods into the right classes, and +setup the inheritance hierarchy, how do you get the DBI to use them? +You have two choices, either a static method call using the name +of your subclass: + + $dbh = MySubDBI->connect(...); + +or specifying a C<RootClass> attribute: + + $dbh = DBI->connect(..., { RootClass => 'MySubDBI' }); + +If both forms are used then the attribute takes precedence. + +The only differences between the two are that using an explicit +RootClass attribute will a) make the DBI automatically attempt to load +a module by that name if the class doesn't exist, and b) won't call +your MySubDBI::connect() method, if you have one. + +When subclassing is being used then, after a successful new +connect, the DBI->connect method automatically calls: + + $dbh->connected($dsn, $user, $pass, \%attr); + +The default method does nothing. The call is made just to simplify +any post-connection setup that your subclass may want to perform. +The parameters are the same as passed to DBI->connect. +If your subclass supplies a connected method, it should be part of the +MySubDBI::db package. + +One more thing to note: you must let the DBI do the handle creation. If you +want to override the connect() method in your *::dr class then it must still +call SUPER::connect to get a $dbh to work with. Similarly, an overridden +prepare() method in *::db must still call SUPER::prepare to get a $sth. +If you try to create your own handles using bless() then you'll find the DBI +will reject them with an "is not a DBI handle (has no magic)" error. + +Here's a brief example of a DBI subclass. A more thorough example +can be found in F<t/subclass.t> in the DBI distribution. + + package MySubDBI; + + use strict; + + use DBI; + use vars qw(@ISA); + @ISA = qw(DBI); + + package MySubDBI::db; + use vars qw(@ISA); + @ISA = qw(DBI::db); + + sub prepare { + my ($dbh, @args) = @_; + my $sth = $dbh->SUPER::prepare(@args) + or return; + $sth->{private_mysubdbi_info} = { foo => 'bar' }; + return $sth; + } + + package MySubDBI::st; + use vars qw(@ISA); + @ISA = qw(DBI::st); + + sub fetch { + my ($sth, @args) = @_; + my $row = $sth->SUPER::fetch(@args) + or return; + do_something_magical_with_row_data($row) + or return $sth->set_err(1234, "The magic failed", undef, "fetch"); + return $row; + } + +When calling a SUPER::method that returns a handle, be careful to +check the return value before trying to do other things with it in +your overridden method. This is especially important if you want to +set a hash attribute on the handle, as Perl's autovivification will +bite you by (in)conveniently creating an unblessed hashref, which your +method will then return with usually baffling results later on like +the error "dbih_getcom handle HASH(0xa4451a8) is not a DBI handle (has +no magic". It's best to check right after the call and return undef +immediately on error, just like DBI would and just like the example +above. + +If your method needs to record an error it should call the set_err() +method with the error code and error string, as shown in the example +above. The error code and error string will be recorded in the +handle and available via C<$h-E<gt>err> and C<$DBI::errstr> etc. +The set_err() method always returns an undef or empty list as +appropriate. Since your method should nearly always return an undef +or empty list as soon as an error is detected it's handy to simply +return what set_err() returns, as shown in the example above. + +If the handle has C<RaiseError>, C<PrintError>, or C<HandleError> +etc. set then the set_err() method will honour them. This means +that if C<RaiseError> is set then set_err() won't return in the +normal way but will 'throw an exception' that can be caught with +an C<eval> block. + +You can stash private data into DBI handles +via C<$h-E<gt>{private_..._*}>. See the entry under L</ATTRIBUTES +COMMON TO ALL HANDLES> for info and important caveats. + + +=head1 TRACING + +The DBI has a powerful tracing mechanism built in. It enables you +to see what's going on 'behind the scenes', both within the DBI and +the drivers you're using. + +=head2 Trace Settings + +Which details are written to the trace output is controlled by a +combination of a I<trace level>, an integer from 0 to 15, and a set +of I<trace flags> that are either on or off. Together these are known +as the I<trace settings> and are stored together in a single integer. +For normal use you only need to set the trace level, and generally +only to a value between 1 and 4. + +Each handle has it's own trace settings, and so does the DBI. +When you call a method the DBI merges the handles settings into its +own for the duration of the call: the trace flags of the handle are +OR'd into the trace flags of the DBI, and if the handle has a higher +trace level then the DBI trace level is raised to match it. +The previous DBI trace settings are restored when the called method +returns. + +=head2 Trace Levels + +Trace I<levels> are as follows: + + 0 - Trace disabled. + 1 - Trace top-level DBI method calls returning with results or errors. + 2 - As above, adding tracing of top-level method entry with parameters. + 3 - As above, adding some high-level information from the driver + and some internal information from the DBI. + 4 - As above, adding more detailed information from the driver. + This is the first level to trace all the rows being fetched. + 5 to 15 - As above but with more and more internal information. + +Trace level 1 is best for a simple overview of what's happening. +Trace levels 2 thru 4 a good choice for general purpose tracing. +Levels 5 and above are best reserved for investigating a specific +problem, when you need to see "inside" the driver and DBI. + +The trace output is detailed and typically very useful. Much of the +trace output is formatted using the L</neat> function, so strings +in the trace output may be edited and truncated by that function. + +=head2 Trace Flags + +Trace I<flags> are used to enable tracing of specific activities +within the DBI and drivers. The DBI defines some trace flags and +drivers can define others. DBI trace flag names begin with a capital +letter and driver specific names begin with a lowercase letter, as +usual. + +Currently the DBI only defines two trace flags: + + ALL - turn on all DBI and driver flags (not recommended) + SQL - trace SQL statements executed + (not yet implemented in DBI but implemented in some DBDs) + CON - trace connection process + ENC - trace encoding (unicode translations etc) + (not yet implemented in DBI but implemented in some DBDs) + DBD - trace only DBD messages + (not implemented by all DBDs yet) + TXN - trace transactions + (not implemented in all DBDs yet) + +The L</parse_trace_flags> and L</parse_trace_flag> methods are used +to convert trace flag names into the corresponding integer bit flags. + +=head2 Enabling Trace + +The C<$h-E<gt>trace> method sets the trace settings for a handle +and C<DBI-E<gt>trace> does the same for the DBI. + +In addition to the L</trace> method, you can enable the same trace +information, and direct the output to a file, by setting the +C<DBI_TRACE> environment variable before starting Perl. +See L</DBI_TRACE> for more information. + +Finally, you can set, or get, the trace settings for a handle using +the C<TraceLevel> attribute. + +All of those methods use parse_trace_flags() and so allow you set +both the trace level and multiple trace flags by using a string +containing the trace level and/or flag names separated by vertical +bar ("C<|>") or comma ("C<,>") characters. For example: + + local $h->{TraceLevel} = "3|SQL|foo"; + +=head2 Trace Output + +Initially trace output is written to C<STDERR>. Both the +C<$h-E<gt>trace> and C<DBI-E<gt>trace> methods take an optional +$trace_file parameter, which may be either the name of a file to be +opened by DBI in append mode, or a reference to an existing writable +(possibly layered) filehandle. If $trace_file is a filename, +and can be opened in append mode, or $trace_file is a writable +filehandle, then I<all> trace output (currently including that from +other handles) is redirected to that file. A warning is generated +if $trace_file can't be opened or is not writable. + +Further calls to trace() without $trace_file do not alter where +the trace output is sent. If $trace_file is undefined, then +trace output is sent to C<STDERR> and, if the prior trace was opened with +$trace_file as a filename, the previous trace file is closed; if $trace_file was +a filehandle, the filehandle is B<not> closed. + +B<NOTE>: If $trace_file is specified as a filehandle, the filehandle +should not be closed until all DBI operations are completed, or the +application has reset the trace file via another call to +C<trace()> that changes the trace file. + +=head2 Tracing to Layered Filehandles + +B<NOTE>: + +=over 4 + +=item * +Tied filehandles are not currently supported, as +tie operations are not available to the PerlIO +methods used by the DBI. + +=item * +PerlIO layer support requires Perl version 5.8 or higher. + +=back + +As of version 5.8, Perl provides the ability to layer various +"disciplines" on an open filehandle via the L<PerlIO> module. + +A simple example of using PerlIO layers is to use a scalar as the output: + + my $scalar = ''; + open( my $fh, "+>:scalar", \$scalar ); + $dbh->trace( 2, $fh ); + +Now all trace output is simply appended to $scalar. + +A more complex application of tracing to a layered filehandle is the +use of a custom layer (I<Refer to >L<Perlio::via> I<for details +on creating custom PerlIO layers.>). Consider an application with the +following logger module: + + package MyFancyLogger; + + sub new + { + my $self = {}; + my $fh; + open $fh, '>', 'fancylog.log'; + $self->{_fh} = $fh; + $self->{_buf} = ''; + return bless $self, shift; + } + + sub log + { + my $self = shift; + return unless exists $self->{_fh}; + my $fh = $self->{_fh}; + $self->{_buf} .= shift; + # + # DBI feeds us pieces at a time, so accumulate a complete line + # before outputing + # + print $fh "At ", scalar localtime(), ':', $self->{_buf}, "\n" and + $self->{_buf} = '' + if $self->{_buf}=~tr/\n//; + } + + sub close { + my $self = shift; + return unless exists $self->{_fh}; + my $fh = $self->{_fh}; + print $fh "At ", scalar localtime(), ':', $self->{_buf}, "\n" and + $self->{_buf} = '' + if $self->{_buf}; + close $fh; + delete $self->{_fh}; + } + + 1; + +To redirect DBI traces to this logger requires creating +a package for the layer: + + package PerlIO::via::MyFancyLogLayer; + + sub PUSHED + { + my ($class,$mode,$fh) = @_; + my $logger; + return bless \$logger,$class; + } + + sub OPEN { + my ($self, $path, $mode, $fh) = @_; + # + # $path is actually our logger object + # + $$self = $path; + return 1; + } + + sub WRITE + { + my ($self, $buf, $fh) = @_; + $$self->log($buf); + return length($buf); + } + + sub CLOSE { + my $self = shift; + $$self->close(); + return 0; + } + + 1; + + +The application can then cause DBI traces to be routed to the +logger using + + use PerlIO::via::MyFancyLogLayer; + + open my $fh, '>:via(MyFancyLogLayer)', MyFancyLogger->new(); + + $dbh->trace('SQL', $fh); + +Now all trace output will be processed by MyFancyLogger's +log() method. + +=head2 Trace Content + +Many of the values embedded in trace output are formatted using the neat() +utility function. This means they may be quoted, sanitized, and possibly +truncated if longer than C<$DBI::neat_maxlen>. See L</neat> for more details. + +=head2 Tracing Tips + +You can add tracing to your own application code using the L</trace_msg> method. + +It can sometimes be handy to compare trace files from two different runs of the +same script. However using a tool like C<diff> on the original log output +doesn't work well because the trace file is full of object addresses that may +differ on each run. + +The DBI includes a handy utility called dbilogstrip that can be used to +'normalize' the log content. It can be used as a filter like this: + + DBI_TRACE=2 perl yourscript.pl ...args1... 2>&1 | dbilogstrip > dbitrace1.log + DBI_TRACE=2 perl yourscript.pl ...args2... 2>&1 | dbilogstrip > dbitrace2.log + diff -u dbitrace1.log dbitrace2.log + +See L<dbilogstrip> for more information. + +=head1 DBI ENVIRONMENT VARIABLES + +The DBI module recognizes a number of environment variables, but most of +them should not be used most of the time. +It is better to be explicit about what you are doing to avoid the need +for environment variables, especially in a web serving system where web +servers are stingy about which environment variables are available. + +=head2 DBI_DSN + +The DBI_DSN environment variable is used by DBI->connect if you do not +specify a data source when you issue the connect. +It should have a format such as "dbi:Driver:databasename". + +=head2 DBI_DRIVER + +The DBI_DRIVER environment variable is used to fill in the database +driver name in DBI->connect if the data source string starts "dbi::" +(thereby omitting the driver). +If DBI_DSN omits the driver name, DBI_DRIVER can fill the gap. + +=head2 DBI_AUTOPROXY + +The DBI_AUTOPROXY environment variable takes a string value that starts +"dbi:Proxy:" and is typically followed by "hostname=...;port=...". +It is used to alter the behaviour of DBI->connect. +For full details, see DBI::Proxy documentation. + +=head2 DBI_USER + +The DBI_USER environment variable takes a string value that is used as +the user name if the DBI->connect call is given undef (as distinct from +an empty string) as the username argument. +Be wary of the security implications of using this. + +=head2 DBI_PASS + +The DBI_PASS environment variable takes a string value that is used as +the password if the DBI->connect call is given undef (as distinct from +an empty string) as the password argument. +Be extra wary of the security implications of using this. + +=head2 DBI_DBNAME (obsolete) + +The DBI_DBNAME environment variable takes a string value that is used only when the +obsolescent style of DBI->connect (with driver name as fourth parameter) is used, and +when no value is provided for the first (database name) argument. + +=head2 DBI_TRACE + +The DBI_TRACE environment variable specifies the global default +trace settings for the DBI at startup. Can also be used to direct +trace output to a file. When the DBI is loaded it does: + + DBI->trace(split /=/, $ENV{DBI_TRACE}, 2) if $ENV{DBI_TRACE}; + +So if C<DBI_TRACE> contains an "C<=>" character then what follows +it is used as the name of the file to append the trace to. + +output appended to that file. If the name begins with a number +followed by an equal sign (C<=>), then the number and the equal sign are +stripped off from the name, and the number is used to set the trace +level. For example: + + DBI_TRACE=1=dbitrace.log perl your_test_script.pl + +On Unix-like systems using a Bourne-like shell, you can do this easily +on the command line: + + DBI_TRACE=2 perl your_test_script.pl + +See L</TRACING> for more information. + +=head2 PERL_DBI_DEBUG (obsolete) + +An old variable that should no longer be used; equivalent to DBI_TRACE. + +=head2 DBI_PROFILE + +The DBI_PROFILE environment variable can be used to enable profiling +of DBI method calls. See L<DBI::Profile> for more information. + +=head2 DBI_PUREPERL + +The DBI_PUREPERL environment variable can be used to enable the +use of DBI::PurePerl. See L<DBI::PurePerl> for more information. + +=head1 WARNING AND ERROR MESSAGES + +=head2 Fatal Errors + +=over 4 + +=item Can't call method "prepare" without a package or object reference + +The C<$dbh> handle you're using to call C<prepare> is probably undefined because +the preceding C<connect> failed. You should always check the return status of +DBI methods, or use the L</RaiseError> attribute. + +=item Can't call method "execute" without a package or object reference + +The C<$sth> handle you're using to call C<execute> is probably undefined because +the preceding C<prepare> failed. You should always check the return status of +DBI methods, or use the L</RaiseError> attribute. + +=item DBI/DBD internal version mismatch + +The DBD driver module was built with a different version of DBI than +the one currently being used. You should rebuild the DBD module under +the current version of DBI. + +(Some rare platforms require "static linking". On those platforms, there +may be an old DBI or DBD driver version actually embedded in the Perl +executable being used.) + +=item DBD driver has not implemented the AutoCommit attribute + +The DBD driver implementation is incomplete. Consult the author. + +=item Can't [sg]et %s->{%s}: unrecognised attribute + +You attempted to set or get an unknown attribute of a handle. Make +sure you have spelled the attribute name correctly; case is significant +(e.g., "Autocommit" is not the same as "AutoCommit"). + +=back + +=head1 Pure-Perl DBI + +A pure-perl emulation of the DBI is included in the distribution +for people using pure-perl drivers who, for whatever reason, can't +install the compiled DBI. See L<DBI::PurePerl>. + +=head1 SEE ALSO + +=head2 Driver and Database Documentation + +Refer to the documentation for the DBD driver that you are using. + +Refer to the SQL Language Reference Manual for the database engine that you are using. + +=head2 ODBC and SQL/CLI Standards Reference Information + +More detailed information about the semantics of certain DBI methods +that are based on ODBC and SQL/CLI standards is available on-line +via microsoft.com, for ODBC, and www.jtc1sc32.org for the SQL/CLI +standard: + + DBI method ODBC function SQL/CLI Working Draft + ---------- ------------- --------------------- + column_info SQLColumns Page 124 + foreign_key_info SQLForeignKeys Page 163 + get_info SQLGetInfo Page 214 + primary_key_info SQLPrimaryKeys Page 254 + table_info SQLTables Page 294 + type_info SQLGetTypeInfo Page 239 + statistics_info SQLStatistics + +To find documentation on the ODBC function you can use +the MSDN search facility at: + + http://msdn.microsoft.com/Search + +and search for something like C<"SQLColumns returns">. + +And for SQL/CLI standard information on SQLColumns you'd read page 124 of +the (very large) SQL/CLI Working Draft available from: + + http://jtc1sc32.org/doc/N0701-0750/32N0744T.pdf + +=head2 Standards Reference Information + +A hyperlinked, browsable version of the BNF syntax for SQL92 (plus +Oracle 7 SQL and PL/SQL) is available here: + + http://cui.unige.ch/db-research/Enseignement/analyseinfo/SQL92/BNFindex.html + +A BNF syntax for SQL3 is available here: + + http://www.sqlstandards.org/SC32/WG3/Progression_Documents/Informal_working_drafts/iso-9075-2-1999.bnf + +The following links provide further useful information about SQL. +Some of these are rather dated now but may still be useful. + + http://www.jcc.com/SQLPages/jccs_sql.htm + http://www.contrib.andrew.cmu.edu/~shadow/sql.html + http://www.altavista.com/query?q=sql+tutorial + + +=head2 Books and Articles + +Programming the Perl DBI, by Alligator Descartes and Tim Bunce. +L<http://books.perl.org/book/154> + +Programming Perl 3rd Ed. by Larry Wall, Tom Christiansen & Jon Orwant. +L<http://books.perl.org/book/134> + +Learning Perl by Randal Schwartz. +L<http://books.perl.org/book/101> + +Details of many other books related to perl can be found at L<http://books.perl.org> + +=head2 Perl Modules + +Index of DBI related modules available from CPAN: + + http://search.cpan.org/search?mode=module&query=DBIx%3A%3A + http://search.cpan.org/search?mode=doc&query=DBI + +For a good comparison of RDBMS-OO mappers and some OO-RDBMS mappers +(including Class::DBI, Alzabo, and DBIx::RecordSet in the former +category and Tangram and SPOPS in the latter) see the Perl +Object-Oriented Persistence project pages at: + + http://poop.sourceforge.net + +A similar page for Java toolkits can be found at: + + http://c2.com/cgi-bin/wiki?ObjectRelationalToolComparison + +=head2 Mailing List + +The I<dbi-users> mailing list is the primary means of communication among +users of the DBI and its related modules. For details send email to: + + dbi-users-help@perl.org + +There are typically between 700 and 900 messages per month. You have +to subscribe in order to be able to post. However you can opt for a +'post-only' subscription. + +Mailing list archives (of variable quality) are held at: + + http://groups.google.com/groups?group=perl.dbi.users + http://www.xray.mpe.mpg.de/mailing-lists/dbi/ + http://www.mail-archive.com/dbi-users%40perl.org/ + +=head2 Assorted Related WWW Links + +The DBI "Home Page": + + http://dbi.perl.org/ + +Other DBI related links: + + http://tegan.deltanet.com/~phlip/DBUIdoc.html + http://dc.pm.org/perl_db.html + http://wdvl.com/Authoring/DB/Intro/toc.html + http://www.hotwired.com/webmonkey/backend/tutorials/tutorial1.html + http://bumppo.net/lists/macperl/1999/06/msg00197.html + http://www.perlmonks.org/?node=DBI%20recipes + http://www.perlmonks.org/?node=Speeding%20up%20the%20DBI + +Other database related links: + + http://www.jcc.com/sql_stnd.html + http://cuiwww.unige.ch/OSG/info/FreeDB/FreeDB.home.html + http://www.connectionstrings.com/ + +Security, especially the "SQL Injection" attack: + + http://www.ngssoftware.com/research/papers.html + http://www.ngssoftware.com/papers/advanced_sql_injection.pdf + http://www.ngssoftware.com/papers/more_advanced_sql_injection.pdf + http://www.esecurityplanet.com/trends/article.php/2243461 + http://www.spidynamics.com/papers/SQLInjectionWhitePaper.pdf + http://www.imperva.com/application_defense_center/white_papers/blind_sql_server_injection.html + http://online.securityfocus.com/infocus/1644 + +Commercial and Data Warehouse Links + + http://www.dwinfocenter.org + http://www.datawarehouse.com + http://www.datamining.org + http://www.olapcouncil.org + http://www.idwa.org + http://www.knowledgecenters.org/dwcenter.asp + +Recommended Perl Programming Links + + http://language.perl.com/style/ + + +=head2 FAQ + +See L<http://faq.dbi-support.com/> + +=head1 AUTHORS + +DBI by Tim Bunce, L<http://www.tim.bunce.name> + +This pod text by Tim Bunce, J. Douglas Dunlop, Jonathan Leffler and others. +Perl by Larry Wall and the C<perl5-porters>. + +=head1 COPYRIGHT + +The DBI module is Copyright (c) 1994-2012 Tim Bunce. Ireland. +All rights reserved. + +You may distribute under the terms of either the GNU General Public +License or the Artistic License, as specified in the Perl 5.10.0 README file. + +=head1 SUPPORT / WARRANTY + +The DBI is free Open Source software. IT COMES WITHOUT WARRANTY OF ANY KIND. + +=head2 Support + +My consulting company, Data Plan Services, offers annual and +multi-annual support contracts for the DBI. These provide sustained +support for DBI development, and sustained value for you in return. +Contact me for details. + +=head2 Sponsor Enhancements + +The DBI Roadmap is available at L<http://search.cpan.org/~timb/DBI/Roadmap.pod> + +If your company would benefit from a specific new DBI feature, +please consider sponsoring its development. Work is performed +rapidly, and usually on a fixed-price payment-on-delivery basis. +Contact me for details. + +Using such targeted financing allows you to contribute to DBI +development, and rapidly get something specific and valuable in return. + +=head1 ACKNOWLEDGEMENTS + +I would like to acknowledge the valuable contributions of the many +people I have worked with on the DBI project, especially in the early +years (1992-1994). In no particular order: Kevin Stock, Buzz Moschetti, +Kurt Andersen, Ted Lemon, William Hails, Garth Kennedy, Michael Peppler, +Neil S. Briscoe, Jeff Urlwin, David J. Hughes, Jeff Stander, +Forrest D Whitcher, Larry Wall, Jeff Fried, Roy Johnson, Paul Hudson, +Georg Rehfeld, Steve Sizemore, Ron Pool, Jon Meek, Tom Christiansen, +Steve Baumgarten, Randal Schwartz, and a whole lot more. + +Then, of course, there are the poor souls who have struggled through +untold and undocumented obstacles to actually implement DBI drivers. +Among their ranks are Jochen Wiedmann, Alligator Descartes, Jonathan +Leffler, Jeff Urlwin, Michael Peppler, Henrik Tougaard, Edwin Pratomo, +Davide Migliavacca, Jan Pazdziora, Peter Haworth, Edmund Mergl, Steve +Williams, Thomas Lowery, and Phlip Plumlee. Without them, the DBI would +not be the practical reality it is today. I'm also especially grateful +to Alligator Descartes for starting work on the first edition of the +"Programming the Perl DBI" book and letting me jump on board. + +The DBI and DBD::Oracle were originally developed while I was Technical +Director (CTO) of Ingeneering in the UK (L<http://www.ig.co.uk>) (formerly known as the +Paul Ingram Group). So I'd especially like to thank Paul for his generosity +and vision in supporting this work for many years. + +A couple of specific DBI features have been sponsored by enlightened companies: + +The development of the swap_inner_handle() method was sponsored by BizRate.com (L<http://BizRate.com>) + +The development of DBD::Gofer and related modules was sponsored by +Shopzilla.com (L<http://Shopzilla.com>), where I currently work. + + +=head1 CONTRIBUTING + +As you can see above, many people have contributed to the DBI and +drivers in many ways over many years. + +If you'd like to help then see L<http://dbi.perl.org/contributing> +and L<http://search.cpan.org/~timb/DBI/Roadmap.pod> + +If you'd like the DBI to do something new or different then a good way +to make that happen is to do it yourself and send me a patch to the +source code that shows the changes. (But read "Speak before you patch" +below.) + +=head2 Browsing the source code repository + +Use http://svn.perl.org/modules/dbi/trunk (basic) +or http://svn.perl.org/viewcvs/modules/ (more useful) + +=head2 How to create a patch using Subversion + +The DBI source code is maintained using Subversion (a replacement +for CVS, see L<http://subversion.tigris.org/>). To access the source +you'll need to install a Subversion client. Then, to get the source +code, do: + + svn checkout http://svn.perl.org/modules/dbi/trunk + +If it prompts for a username and password use your perl.org account +if you have one, else just 'guest' and 'guest'. The source code will +be in a new subdirectory called C<trunk>. + +To keep informed about changes to the source you can send an empty email +to svn-commit-modules-dbi-subscribe@perl.org after which you'll get an email +with the change log message and diff of each change checked-in to the source. + +After making your changes you can generate a patch file, but before +you do, make sure your source is still up to date using: + + svn update + +If you get any conflicts reported you'll need to fix them first. +Then generate the patch file from within the C<trunk> directory using: + + svn diff > foo.patch + +Read the patch file, as a sanity check, and then email it to dbi-dev@perl.org. + +=head2 How to create a patch without Subversion + +Unpack a fresh copy of the distribution: + + tar xfz DBI-1.40.tar.gz + +Rename the newly created top level directory: + + mv DBI-1.40 DBI-1.40.your_foo + +Edit the contents of DBI-1.40.your_foo/* till it does what you want. + +Test your changes and then remove all temporary files: + + make test && make distclean + +Go back to the directory you originally unpacked the distribution: + + cd .. + +Unpack I<another> copy of the original distribution you started with: + + tar xfz DBI-1.40.tar.gz + +Then create a patch file by performing a recursive C<diff> on the two +top level directories: + + diff -r -u DBI-1.40 DBI-1.40.your_foo > DBI-1.40.your_foo.patch + +=head2 Speak before you patch + +For anything non-trivial or possibly controversial it's a good idea +to discuss (on dbi-dev@perl.org) the changes you propose before +actually spending time working on them. Otherwise you run the risk +of them being rejected because they don't fit into some larger plans +you may not be aware of. + +=head1 TRANSLATIONS + +A German translation of this manual (possibly slightly out of date) is +available, thanks to O'Reilly, at: + + http://www.oreilly.de/catalog/perldbiger/ + +Some other translations: + + http://cronopio.net/perl/ - Spanish + http://member.nifty.ne.jp/hippo2000/dbimemo.htm - Japanese + + +=head1 TRAINING + +References to DBI related training resources. No recommendation implied. + + http://www.treepax.co.uk/ + http://www.keller.com/dbweb/ + +(If you offer professional DBI related training services, +please send me your details so I can add them here.) + +=head1 OTHER RELATED WORK AND PERL MODULES + +=over 4 + +=item Apache::DBI by E.Mergl@bawue.de + +To be used with the Apache daemon together with an embedded Perl +interpreter like C<mod_perl>. Establishes a database connection which +remains open for the lifetime of the HTTP daemon. This way the CGI +connect and disconnect for every database access becomes superfluous. + +=item SQL Parser + +See also the L<SQL::Statement> module, SQL parser and engine. + +=back + +=cut + +# LocalWords: DBI |