A fix and a test case for

 Bug#19022 "Memory bug when switching db during trigger execution"
 Bug#17199 "Problem when view calls function from another database."
 Bug#18444 "Fully qualified stored function names don't work correctly in
            SELECT statements"

 Documentation note: this patch introduces a change in behaviour of prepared
 statements.

 This patch adds a few new invariants with regard to how THD::db should
 be used. These invariants should be preserved in future:

  - one should never refer to THD::db by pointer and always make a deep copy
    (strmake, strdup)
  - one should never compare two databases by pointer, but use strncmp or
    my_strncasecmp
  - TABLE_LIST object table->db should be always initialized in the parser or
    by creator of the object.

    For prepared statements it means that if the current database is changed
    after a statement is prepared, the database that was current at prepare
    remains active. This also means that you can not prepare a statement that
    implicitly refers to the current database if the latter is not set.
    This is not documented, and therefore needs documentation. This is NOT a
    change in behavior for almost all SQL statements except:
     - ALTER TABLE t1 RENAME t2 
     - OPTIMIZE TABLE t1
     - ANALYZE TABLE t1
     - TRUNCATE TABLE t1 --
     until this patch t1 or t2 could be evaluated at the first execution of
     prepared statement. 

     CURRENT_DATABASE() still works OK and is evaluated at every execution
     of prepared statement.

     Note, that in stored routines this is not an issue as the default
     database is the database of the stored procedure and "use" statement
     is prohibited in stored routines.

  This patch makes obsolete the use of check_db_used (it was never used in the
  old code too) and all other places that check for table->db and assign it
  from THD::db if it's NULL, except the parser.

 How this patch was created: THD::{db,db_length} were replaced with a
 LEX_STRING, THD::db. All the places that refer to THD::{db,db_length} were
 manually checked and:
  - if the place uses thd->db by pointer, it was fixed to make a deep copy
  - if a place compared two db pointers, it was fixed to compare them by value
    (via strcmp/my_strcasecmp, whatever was approproate)
 Then this intermediate patch was used to write a smaller patch that does the
 same thing but without a rename.

 TODO in 5.1:
   - remove check_db_used
   - deploy THD::set_db in mysql_change_db

 See also comments to individual files.


mysql-test/r/create.result:
  Modify the result file: a database can never be NULL.
mysql-test/r/ps.result:
  Update test results (Bug#17199 et al)
mysql-test/r/sp.result:
  Update test results (Bug#17199 et al)
mysql-test/t/create.test:
  Update the id of the returned error.
mysql-test/t/ps.test:
  Add test coverage for prepared statements and current database. In scope of
  work on Bug#17199 "Problem when view calls function from another database."
mysql-test/t/sp.test:
  Add a test case for Bug#17199 "Problem when view calls function from another
  database." and Bug#18444 "Fully qualified stored function names don't work
  correctly in SELECT statements". Test a complementary problem.
sql/item_strfunc.cc:
  Touch the code that reads thd->db (cleanup).
sql/log_event.cc:
  While we are at it, replace direct access to thd->db with a method.
  Should simplify future conversion of THD::db to LEX_STRING.
sql/slave.cc:
  While we are at it, replace direct access to thd->db with a method.
  Should simplify future conversion of THD::db to LEX_STRING.
sql/slave.h:
  Remove a declaration for a method that is used only in one module.
sql/sp.cc:
  Rewrite sp_use_new_db: this is a cleanup that I needed in order to understand
  this function and ensure that it has no bugs.
sql/sp.h:
  Add a new declaration for sp_use_new_db (uses LEX_STRINGs) and a comment.
sql/sp_head.cc:
  - drop sp_name_current_db_new - a creator of sp_name class that was used
  when sp_name was created for an identifier without an explicitly initialized
  database. Now we pass thd->db to constructor of sp_name right in the 
  parser.
  - rewrite sp_head::init_strings: name->m_db is always set now
  - use the new variant of sp_use_new_db
  - we don't need to update thd->db with SP MEM_ROOT pointer anymore when
  parsing a stored procedure, as noone will refer to it (yes!)
sql/sp_head.h:
  - remove unneded methods and members
sql/sql_class.h:
  - introduce 3 THD  methods to work with THD::db:
    .set_db to assign the current database
    .reset_db to reset the current database (temporarily) or set it to NULL
    .opt_copy_db_to - to deep-copy thd->db to a pointer if it's not NULL
sql/sql_db.cc:
  While we are at it, replace direct access to thd->db with a method.
  Should simplify future conversion of THD::db to LEX_STRING.
sql/sql_insert.cc:
  - replace checks with asserts: table_list->db must be always set in the parser.
sql/sql_lex.h:
  - add a comment
sql/sql_parse.cc:
  - implement the invariant described in the changeset comment.
  - remove juggling with lex->sphead in SQLCOM_CREATE_PROCEDURE:
    now db_load_routine uses its own LEX object and doesn't damage the main
    LEX.
  - add DBUG_ASSERT(0) to unused "check_db_used"
sql/sql_table.cc:
  - replace a check with an assert (table_ident->db)
sql/sql_trigger.cc:
  While we are at it, replace direct access to thd->db with a method.
  Should simplify future conversion of THD::db to LEX_STRING.
sql/sql_udf.cc:
  - use thd->set_db instead of direct modification of to thd->db
sql/sql_view.cc:
  - replace a check with an assert (view->db)
sql/sql_yacc.yy:
  - make sure that we always copy table->db or name->db or ident->db or
    select_lex->db from thd->db if the former is not set. If thd->db
    is not set but is accessed, return an error.
sql/tztime.cc:
  - be nice, never copy thd->db by pointer.

1 files changed, 118 insertions, 0 deletions

diff --git a/mysql-test/t/ps.test b/mysql-test/t/ps.test
index e3f3e37cd4c..ff66b265fae 100644
--- a/mysql-test/t/ps.test
+++ b/mysql-test/t/ps.test
@@ -1146,4 +1146,122 @@ execute stmt;
 execute stmt;
 deallocate prepare stmt;
 drop table t1, t2, t3;
+
+#
+# Bug#17199 "Table not found" error occurs if the query contains a call
+#            to a function from another database.
+#            Test prepared statements- related behaviour.
+#
+#
+# ALTER TABLE RENAME and Prepared Statements: wrong DB name buffer was used
+# in ALTER ... RENAME which caused memory corruption in prepared statements.
+# No need to fix this problem in 4.1 as ALTER TABLE is not allowed in
+# Prepared Statements in 4.1.
+#
+create database mysqltest_long_database_name_to_thrash_heap;
+use test;
+create table t1 (i int);
+prepare stmt from "alter table test.t1 rename t1";
+use mysqltest_long_database_name_to_thrash_heap;
+execute stmt;
+show tables like 't1';
+prepare stmt from "alter table test.t1 rename t1";
+use test;
+execute stmt;
+show tables like 't1';
+use mysqltest_long_database_name_to_thrash_heap;
+show tables like 't1';
+deallocate prepare stmt;
+#
+# Check that a prepared statement initializes its current database at
+# PREPARE, and then works correctly even if the current database has been
+# changed.
+# 
+use mysqltest_long_database_name_to_thrash_heap; 
+# Necessary for preparation of INSERT/UPDATE/DELETE to succeed
+prepare stmt_create from "create table t1 (i int)";
+prepare stmt_insert from "insert into t1 (i) values (1)";
+prepare stmt_update from "update t1 set i=2";
+prepare stmt_delete from "delete from t1 where i=2";
+prepare stmt_select from "select * from t1";
+prepare stmt_alter from "alter table t1 add column (b int)";
+prepare stmt_alter1 from "alter table t1 drop column b";
+prepare stmt_analyze from "analyze table t1";
+prepare stmt_optimize from "optimize table t1";
+prepare stmt_show from "show tables like 't1'";
+prepare stmt_truncate from "truncate table t1";
+prepare stmt_drop from "drop table t1";
+# Drop the table that was used to prepare INSERT/UPDATE/DELETE: we will
+# create a new one by executing stmt_create
+drop table t1;
+# Switch the current database
+use test;
+# Check that all prepared statements operate on the database that was
+# active at PREPARE
+execute stmt_create;
+# should return empty set
+show tables like 't1';
+use mysqltest_long_database_name_to_thrash_heap;
+show tables like 't1';
+use test;
+execute stmt_insert;
+select * from mysqltest_long_database_name_to_thrash_heap.t1;
+execute stmt_update;
+select * from mysqltest_long_database_name_to_thrash_heap.t1;
+execute stmt_delete;
+execute stmt_select;
+execute stmt_alter;
+show columns from mysqltest_long_database_name_to_thrash_heap.t1;
+execute stmt_alter1;
+show columns from mysqltest_long_database_name_to_thrash_heap.t1;
+execute stmt_analyze;
+execute stmt_optimize;
+execute stmt_show;
+execute stmt_truncate;
+execute stmt_drop;
+show tables like 't1';
+use mysqltest_long_database_name_to_thrash_heap;
+show tables like 't1';
+#
+# Attempt a statement PREPARE when there is no current database:
+# is expected to return an error.
+#
+drop database mysqltest_long_database_name_to_thrash_heap;
+--error ER_NO_DB_ERROR
+prepare stmt_create from "create table t1 (i int)";
+--error ER_NO_DB_ERROR
+prepare stmt_insert from "insert into t1 (i) values (1)";
+--error ER_NO_DB_ERROR
+prepare stmt_update from "update t1 set i=2";
+--error ER_NO_DB_ERROR
+prepare stmt_delete from "delete from t1 where i=2";
+--error ER_NO_DB_ERROR
+prepare stmt_select from "select * from t1";
+--error ER_NO_DB_ERROR
+prepare stmt_alter from "alter table t1 add column (b int)";
+--error ER_NO_DB_ERROR
+prepare stmt_alter1 from "alter table t1 drop column b";
+--error ER_NO_DB_ERROR
+prepare stmt_analyze from "analyze table t1";
+--error ER_NO_DB_ERROR
+prepare stmt_optimize from "optimize table t1";
+--error ER_NO_DB_ERROR
+prepare stmt_show from "show tables like 't1'";
+--error ER_NO_DB_ERROR
+prepare stmt_truncate from "truncate table t1";
+--error ER_NO_DB_ERROR
+prepare stmt_drop from "drop table t1";
+#
+# The above has automatically deallocated all our statements.
+#
+# Attempt to CREATE a temporary table when no DB used: it should fail
+# This proves that no table can be used without explicit specification of
+# its database if there is no current database. 
+#
+--error ER_NO_DB_ERROR
+create temporary table t1 (i int);
+#
+# Restore the old environemnt
+#
+use test;
 # End of 5.0 tests