From 4f15a043e2637d67e2c882a7fd8514ef1c4c0eb7 Mon Sep 17 00:00:00 2001 From: unknown Date: Tue, 9 May 2006 16:39:11 +0400 Subject: Fix for bugs#12472/#15137 'CREATE TABLE ... SELECT ... which explicitly or implicitly uses stored function gives "Table not locked" error' CREATE TABLE ... SELECT ... statement which was explicitly or implicitly (through view) using stored function gave "Table not locked" error. The actual bug resides in the current locking scheme of CREATE TABLE SELECT code, which first opens and locks tables of the SELECT statement itself, and then, having SELECT tables locked, creates the .FRM, opens the .FRM and acquires lock on it. This scheme opens a possibility for a deadlock, which was present and ignored since version 3.23 or earlier. This scheme also conflicts with the invariant of the prelocking algorithm -- no table can be open and locked while there are tables locked in prelocked mode. The patch makes an exception for this invariant when doing CREATE TABLE ... SELECT, thus extending the possibility of a deadlock to the prelocked mode. We can't supply a better fix in 5.0. mysql-test/r/sp.result: Added tests for bugs#12472/#15137 'CREATE TABLE ... SELECT ... which explicitly or implicitly uses stored function gives "Table not locked" error' mysql-test/t/sp.test: Added tests for bugs#12472/#15137 'CREATE TABLE ... SELECT ... which explicitly or implicitly uses stored function gives "Table not locked" error' sql/mysql_priv.h: Added flag which can be passed to open_table() routine in order to ignore set of locked tables and prelocked mode. We don't need declaration of create_table_from_items() any longer as it was moved into sql_insert.cc and made static. sql/sql_base.cc: open_table(): Added flag which allows open table ignoring set of locked tables and prelocked mode. sql/sql_insert.cc: Moved create_table_from_items() from sql_table.cc to sql_insert.cc as it was not used outside of sql_insert.cc and contains code which is specific for CREATE TABLE ... SELECT. Also now when we are executing CREATE TABLE ... SELECT ... statement which SELECT part requires execution in prelocked mode we ignore set of locked tables in order to get access to the table we just have created. We probably don't want to do this if we are under real LOCK TABLES since it will widen window for deadlock too much. sql/sql_table.cc: Moved create_table_from_items() routine into sql_insert.cc, since it was not used anywhere outside of this file and contains logic which is specific for CREATE TABLE ... SELECT statement. --- sql/sql_insert.cc | 147 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 147 insertions(+) (limited to 'sql/sql_insert.cc') diff --git a/sql/sql_insert.cc b/sql/sql_insert.cc index ad9606acb83..c157025fbdc 100644 --- a/sql/sql_insert.cc +++ b/sql/sql_insert.cc @@ -2434,6 +2434,153 @@ bool select_insert::send_eof() CREATE TABLE (SELECT) ... ***************************************************************************/ +/* + Create table from lists of fields and items (or open existing table + with same name). + + SYNOPSIS + create_table_from_items() + thd in Thread object + create_info in Create information (like MAX_ROWS, ENGINE or + temporary table flag) + create_table in Pointer to TABLE_LIST object providing database + and name for table to be created or to be open + extra_fields in/out Initial list of fields for table to be created + keys in List of keys for table to be created + items in List of items which should be used to produce rest + of fields for the table (corresponding fields will + be added to the end of 'extra_fields' list) + lock out Pointer to the MYSQL_LOCK object for table created + (open) will be returned in this parameter. Since + this table is not included in THD::lock caller is + responsible for explicitly unlocking this table. + + NOTES + If 'create_info->options' bitmask has HA_LEX_CREATE_IF_NOT_EXISTS + flag and table with name provided already exists then this function will + simply open existing table. + Also note that create, open and lock sequence in this function is not + atomic and thus contains gap for deadlock and can cause other troubles. + Since this function contains some logic specific to CREATE TABLE ... SELECT + it should be changed before it can be used in other contexts. + + RETURN VALUES + non-zero Pointer to TABLE object for table created or opened + 0 Error +*/ + +static TABLE *create_table_from_items(THD *thd, HA_CREATE_INFO *create_info, + TABLE_LIST *create_table, + List *extra_fields, + List *keys, List *items, + MYSQL_LOCK **lock) +{ + TABLE tmp_table; // Used during 'create_field()' + TABLE *table= 0; + uint select_field_count= items->elements; + /* Add selected items to field list */ + List_iterator_fast it(*items); + Item *item; + Field *tmp_field; + bool not_used; + DBUG_ENTER("create_table_from_items"); + + tmp_table.alias= 0; + tmp_table.timestamp_field= 0; + tmp_table.s= &tmp_table.share_not_to_be_used; + tmp_table.s->db_create_options=0; + tmp_table.s->blob_ptr_size= portable_sizeof_char_ptr; + tmp_table.s->db_low_byte_first= test(create_info->db_type == DB_TYPE_MYISAM || + create_info->db_type == DB_TYPE_HEAP); + tmp_table.null_row=tmp_table.maybe_null=0; + + while ((item=it++)) + { + create_field *cr_field; + Field *field; + if (item->type() == Item::FUNC_ITEM) + field=item->tmp_table_field(&tmp_table); + else + field=create_tmp_field(thd, &tmp_table, item, item->type(), + (Item ***) 0, &tmp_field, 0, 0, 0, 0, 0); + if (!field || + !(cr_field=new create_field(field,(item->type() == Item::FIELD_ITEM ? + ((Item_field *)item)->field : + (Field*) 0)))) + DBUG_RETURN(0); + if (item->maybe_null) + cr_field->flags &= ~NOT_NULL_FLAG; + extra_fields->push_back(cr_field); + } + /* + create and lock table + + We don't log the statement, it will be logged later. + + If this is a HEAP table, the automatic DELETE FROM which is written to the + binlog when a HEAP table is opened for the first time since startup, must + not be written: 1) it would be wrong (imagine we're in CREATE SELECT: we + don't want to delete from it) 2) it would be written before the CREATE + TABLE, which is a wrong order. So we keep binary logging disabled when we + open_table(). + NOTE: By locking table which we just have created (or for which we just have + have found that it already exists) separately from other tables used by the + statement we create potential window for deadlock. + TODO: create and open should be done atomic ! + */ + { + tmp_disable_binlog(thd); + if (!mysql_create_table(thd, create_table->db, create_table->table_name, + create_info, *extra_fields, *keys, 0, + select_field_count)) + { + /* + If we are here in prelocked mode we either create temporary table + or prelocked mode is caused by the SELECT part of this statement. + */ + DBUG_ASSERT(!thd->prelocked_mode || + create_info->options & HA_LEX_CREATE_TMP_TABLE || + thd->lex->requires_prelocking()); + + /* + NOTE: We don't want to ignore set of locked tables here if we are + under explicit LOCK TABLES since it will open gap for deadlock + too wide (and also is not backward compatible). + */ + if (! (table= open_table(thd, create_table, thd->mem_root, (bool*) 0, + (MYSQL_LOCK_IGNORE_FLUSH | + ((thd->prelocked_mode == PRELOCKED) ? + MYSQL_OPEN_IGNORE_LOCKED_TABLES:0))))) + quick_rm_table(create_info->db_type, create_table->db, + table_case_name(create_info, create_table->table_name)); + } + reenable_binlog(thd); + if (!table) // open failed + DBUG_RETURN(0); + } + + /* + FIXME: What happens if trigger manages to be created while we are + obtaining this lock ? May be it is sensible just to disable + trigger execution in this case ? Or will MYSQL_LOCK_IGNORE_FLUSH + save us from that ? + */ + table->reginfo.lock_type=TL_WRITE; + if (! ((*lock)= mysql_lock_tables(thd, &table, 1, + MYSQL_LOCK_IGNORE_FLUSH, ¬_used))) + { + VOID(pthread_mutex_lock(&LOCK_open)); + hash_delete(&open_cache,(byte*) table); + VOID(pthread_mutex_unlock(&LOCK_open)); + quick_rm_table(create_info->db_type, create_table->db, + table_case_name(create_info, create_table->table_name)); + DBUG_RETURN(0); + } + table->file->extra(HA_EXTRA_WRITE_CACHE); + DBUG_RETURN(table); +} + + int select_create::prepare(List &values, SELECT_LEX_UNIT *u) { -- cgit v1.2.1