Merge bk-internal.mysql.com:/home/bk/mysql-5.1-runtime

into  ibm.opbmk:/home/alik/Documents/MySQL/devel/5.1-rt-bug25843


sql/mysql_priv.h:
  Auto merged
sql/sp.cc:
  Auto merged
sql/sp_head.cc:
  Auto merged
sql/sql_class.cc:
  Auto merged
sql/sql_class.h:
  Auto merged
sql/sql_db.cc:
  Auto merged

mysql-test/include/query_cache_sql_prepare.inc

@@ -275,5 +275,223 @@ drop table t1;
 --echo ---- disconnect connection con1 ----
 disconnect con1;
 
+#
+# Bug #25843 Changing default database between PREPARE and EXECUTE of statement
+# breaks binlog.
+#
+# There were actually two problems discovered by this bug:
+#
+#   1. Default (current) database is not fixed at the creation time.
+#      That leads to wrong output of DATABASE() function.
+#
+#   2. Database attributes (@@collation_database) are not fixed at the creation
+#      time. That leads to wrong resultset.
+#
+# Binlog breakage and Query Cache wrong output happened because of the first
+# problem.
+#
+
+--echo ########################################################################
+--echo #
+--echo # BUG#25843: Changing default database between PREPARE and EXECUTE of
+--echo # statement breaks binlog.
+--echo #
+--echo ########################################################################
+
+###############################################################################
+
+--echo
+--echo #
+--echo # Check that default database and its attributes are fixed at the
+--echo # creation time.
+--echo #
+
+# Prepare data structures.
+
+--echo
+--disable_warnings
+DROP DATABASE IF EXISTS mysqltest1;
+DROP DATABASE IF EXISTS mysqltest2;
+--enable_warnings
+
+--echo
+CREATE DATABASE mysqltest1 COLLATE utf8_unicode_ci;
+CREATE DATABASE mysqltest2 COLLATE utf8_general_ci;
+
+--echo
+CREATE TABLE mysqltest1.t1(msg VARCHAR(255));
+CREATE TABLE mysqltest2.t1(msg VARCHAR(255));
+
+# - Create a prepared statement with mysqltest1 as default database;
+
+--echo
+
+use mysqltest1;
+
+PREPARE stmt_a_1 FROM 'INSERT INTO t1 VALUES(DATABASE())';
+PREPARE stmt_a_2 FROM 'INSERT INTO t1 VALUES(@@collation_database)';
+
+# - Execute on mysqltest1.
+
+--echo
+
+EXECUTE stmt_a_1;
+EXECUTE stmt_a_2;
+
+# - Execute on mysqltest2.
+
+--echo
+
+use mysqltest2;
+
+EXECUTE stmt_a_1;
+EXECUTE stmt_a_2;
+
+# - Check the results;
+
+--echo
+SELECT * FROM mysqltest1.t1;
+
+--echo
+SELECT * FROM mysqltest2.t1;
+
+# - Drop prepared statements.
+
+--echo
+DROP PREPARE stmt_a_1;
+DROP PREPARE stmt_a_2;
+
+###############################################################################
+
+--echo
+--echo #
+--echo # The Query Cache test case.
+--echo #
+
+--echo
+DELETE FROM mysqltest1.t1;
+DELETE FROM mysqltest2.t1;
+
+--echo
+INSERT INTO mysqltest1.t1 VALUES('mysqltest1.t1');
+INSERT INTO mysqltest2.t1 VALUES('mysqltest2.t1');
+
+--echo
+use mysqltest1;
+PREPARE stmt_b_1 FROM 'SELECT * FROM t1';
+
+--echo
+use mysqltest2;
+PREPARE stmt_b_2 FROM 'SELECT * FROM t1';
+
+--echo
+EXECUTE stmt_b_1;
+
+--echo
+EXECUTE stmt_b_2;
+
+--echo
+use mysqltest1;
+
+--echo
+EXECUTE stmt_b_1;
+
+--echo
+EXECUTE stmt_b_2;
+
+--echo
+DROP PREPARE stmt_b_1;
+DROP PREPARE stmt_b_2;
+
+# Cleanup.
+
+--echo
+use test;
+
+--echo
+DROP DATABASE mysqltest1;
+DROP DATABASE mysqltest2;
+
+###############################################################################
+
+--echo
+--echo #
+--echo # Check that prepared statements work properly when there is no current
+--echo # database.
+--echo #
+
+--echo
+CREATE DATABASE mysqltest1 COLLATE utf8_unicode_ci;
+CREATE DATABASE mysqltest2 COLLATE utf8_general_ci;
+
+--echo
+use mysqltest1;
+
+--echo
+PREPARE stmt_c_1 FROM 'SELECT DATABASE(), @@collation_database';
+
+--echo
+use mysqltest2;
+
+--echo
+PREPARE stmt_c_2 FROM 'SELECT DATABASE(), @@collation_database';
+
+--echo
+DROP DATABASE mysqltest2;
+
+--echo
+SELECT DATABASE(), @@collation_database;
+
+# -- Here we have: current db: NULL; stmt db: mysqltest1;
+--echo
+EXECUTE stmt_c_1;
+
+--echo
+SELECT DATABASE(), @@collation_database;
+
+# -- Here we have: current db: NULL; stmt db: mysqltest2 (non-existent);
+--echo
+EXECUTE stmt_c_2;
+
+--echo
+SELECT DATABASE(), @@collation_database;
+
+# -- Create prepared statement, which has no current database.
+
+--echo
+PREPARE stmt_c_3 FROM 'SELECT DATABASE(), @@collation_database';
+
+# -- Here we have: current db: NULL; stmt db: NULL;
+--echo
+EXECUTE stmt_c_3;
+
+--echo
+use mysqltest1;
+
+# -- Here we have: current db: mysqltest1; stmt db: mysqltest2 (non-existent);
+--echo
+EXECUTE stmt_c_2;
+
+--echo
+SELECT DATABASE(), @@collation_database;
+
+# -- Here we have: current db: mysqltest1; stmt db: NULL;
+--echo
+EXECUTE stmt_c_3;
+
+--echo
+SELECT DATABASE(), @@collation_database;
+
+--echo
+DROP DATABASE mysqltest1;
+
+--echo
+use test;
+
+--echo
+--echo ########################################################################
+
+###############################################################################
+
 set @@global.query_cache_size=@initial_query_cache_size;
 flush status; # reset Qcache status variables for next tests

mysql-test/r/query_cache_ps_no_prot.result

@@ -371,5 +371,163 @@ Variable_name	Value
 Qcache_hits	21
 drop table t1;
 ---- disconnect connection con1 ----
+########################################################################
+#
+# BUG#25843: Changing default database between PREPARE and EXECUTE of
+# statement breaks binlog.
+#
+########################################################################
+
+#
+# Check that default database and its attributes are fixed at the
+# creation time.
+#
+
+DROP DATABASE IF EXISTS mysqltest1;
+DROP DATABASE IF EXISTS mysqltest2;
+
+CREATE DATABASE mysqltest1 COLLATE utf8_unicode_ci;
+CREATE DATABASE mysqltest2 COLLATE utf8_general_ci;
+
+CREATE TABLE mysqltest1.t1(msg VARCHAR(255));
+CREATE TABLE mysqltest2.t1(msg VARCHAR(255));
+
+use mysqltest1;
+PREPARE stmt_a_1 FROM 'INSERT INTO t1 VALUES(DATABASE())';
+PREPARE stmt_a_2 FROM 'INSERT INTO t1 VALUES(@@collation_database)';
+
+EXECUTE stmt_a_1;
+EXECUTE stmt_a_2;
+
+use mysqltest2;
+EXECUTE stmt_a_1;
+EXECUTE stmt_a_2;
+
+SELECT * FROM mysqltest1.t1;
+msg
+mysqltest1
+utf8_unicode_ci
+mysqltest1
+utf8_unicode_ci
+
+SELECT * FROM mysqltest2.t1;
+msg
+
+DROP PREPARE stmt_a_1;
+DROP PREPARE stmt_a_2;
+
+#
+# The Query Cache test case.
+#
+
+DELETE FROM mysqltest1.t1;
+DELETE FROM mysqltest2.t1;
+
+INSERT INTO mysqltest1.t1 VALUES('mysqltest1.t1');
+INSERT INTO mysqltest2.t1 VALUES('mysqltest2.t1');
+
+use mysqltest1;
+PREPARE stmt_b_1 FROM 'SELECT * FROM t1';
+
+use mysqltest2;
+PREPARE stmt_b_2 FROM 'SELECT * FROM t1';
+
+EXECUTE stmt_b_1;
+msg
+mysqltest1.t1
+
+EXECUTE stmt_b_2;
+msg
+mysqltest2.t1
+
+use mysqltest1;
+
+EXECUTE stmt_b_1;
+msg
+mysqltest1.t1
+
+EXECUTE stmt_b_2;
+msg
+mysqltest2.t1
+
+DROP PREPARE stmt_b_1;
+DROP PREPARE stmt_b_2;
+
+use test;
+
+DROP DATABASE mysqltest1;
+DROP DATABASE mysqltest2;
+
+#
+# Check that prepared statements work properly when there is no current
+# database.
+#
+
+CREATE DATABASE mysqltest1 COLLATE utf8_unicode_ci;
+CREATE DATABASE mysqltest2 COLLATE utf8_general_ci;
+
+use mysqltest1;
+
+PREPARE stmt_c_1 FROM 'SELECT DATABASE(), @@collation_database';
+
+use mysqltest2;
+
+PREPARE stmt_c_2 FROM 'SELECT DATABASE(), @@collation_database';
+
+DROP DATABASE mysqltest2;
+
+SELECT DATABASE(), @@collation_database;
+DATABASE()	@@collation_database
+NULL	latin1_swedish_ci
+
+EXECUTE stmt_c_1;
+DATABASE()	@@collation_database
+mysqltest1	utf8_unicode_ci
+
+SELECT DATABASE(), @@collation_database;
+DATABASE()	@@collation_database
+NULL	latin1_swedish_ci
+
+EXECUTE stmt_c_2;
+DATABASE()	@@collation_database
+NULL	latin1_swedish_ci
+Warnings:
+Note	1049	Unknown database 'mysqltest2'
+
+SELECT DATABASE(), @@collation_database;
+DATABASE()	@@collation_database
+NULL	latin1_swedish_ci
+
+PREPARE stmt_c_3 FROM 'SELECT DATABASE(), @@collation_database';
+
+EXECUTE stmt_c_3;
+DATABASE()	@@collation_database
+NULL	latin1_swedish_ci
+
+use mysqltest1;
+
+EXECUTE stmt_c_2;
+DATABASE()	@@collation_database
+NULL	latin1_swedish_ci
+Warnings:
+Note	1049	Unknown database 'mysqltest2'
+
+SELECT DATABASE(), @@collation_database;
+DATABASE()	@@collation_database
+mysqltest1	utf8_unicode_ci
+
+EXECUTE stmt_c_3;
+DATABASE()	@@collation_database
+NULL	latin1_swedish_ci
+
+SELECT DATABASE(), @@collation_database;
+DATABASE()	@@collation_database
+mysqltest1	utf8_unicode_ci
+
+DROP DATABASE mysqltest1;
+
+use test;
+
+########################################################################
 set @@global.query_cache_size=@initial_query_cache_size;
 flush status;

mysql-test/r/query_cache_ps_ps_prot.result

@@ -371,5 +371,163 @@ Variable_name	Value
 Qcache_hits	19
 drop table t1;
 ---- disconnect connection con1 ----
+########################################################################
+#
+# BUG#25843: Changing default database between PREPARE and EXECUTE of
+# statement breaks binlog.
+#
+########################################################################
+
+#
+# Check that default database and its attributes are fixed at the
+# creation time.
+#
+
+DROP DATABASE IF EXISTS mysqltest1;
+DROP DATABASE IF EXISTS mysqltest2;
+
+CREATE DATABASE mysqltest1 COLLATE utf8_unicode_ci;
+CREATE DATABASE mysqltest2 COLLATE utf8_general_ci;
+
+CREATE TABLE mysqltest1.t1(msg VARCHAR(255));
+CREATE TABLE mysqltest2.t1(msg VARCHAR(255));
+
+use mysqltest1;
+PREPARE stmt_a_1 FROM 'INSERT INTO t1 VALUES(DATABASE())';
+PREPARE stmt_a_2 FROM 'INSERT INTO t1 VALUES(@@collation_database)';
+
+EXECUTE stmt_a_1;
+EXECUTE stmt_a_2;
+
+use mysqltest2;
+EXECUTE stmt_a_1;
+EXECUTE stmt_a_2;
+
+SELECT * FROM mysqltest1.t1;
+msg
+mysqltest1
+utf8_unicode_ci
+mysqltest1
+utf8_unicode_ci
+
+SELECT * FROM mysqltest2.t1;
+msg
+
+DROP PREPARE stmt_a_1;
+DROP PREPARE stmt_a_2;
+
+#
+# The Query Cache test case.
+#
+
+DELETE FROM mysqltest1.t1;
+DELETE FROM mysqltest2.t1;
+
+INSERT INTO mysqltest1.t1 VALUES('mysqltest1.t1');
+INSERT INTO mysqltest2.t1 VALUES('mysqltest2.t1');
+
+use mysqltest1;
+PREPARE stmt_b_1 FROM 'SELECT * FROM t1';
+
+use mysqltest2;
+PREPARE stmt_b_2 FROM 'SELECT * FROM t1';
+
+EXECUTE stmt_b_1;
+msg
+mysqltest1.t1
+
+EXECUTE stmt_b_2;
+msg
+mysqltest2.t1
+
+use mysqltest1;
+
+EXECUTE stmt_b_1;
+msg
+mysqltest1.t1
+
+EXECUTE stmt_b_2;
+msg
+mysqltest2.t1
+
+DROP PREPARE stmt_b_1;
+DROP PREPARE stmt_b_2;
+
+use test;
+
+DROP DATABASE mysqltest1;
+DROP DATABASE mysqltest2;
+
+#
+# Check that prepared statements work properly when there is no current
+# database.
+#
+
+CREATE DATABASE mysqltest1 COLLATE utf8_unicode_ci;
+CREATE DATABASE mysqltest2 COLLATE utf8_general_ci;
+
+use mysqltest1;
+
+PREPARE stmt_c_1 FROM 'SELECT DATABASE(), @@collation_database';
+
+use mysqltest2;
+
+PREPARE stmt_c_2 FROM 'SELECT DATABASE(), @@collation_database';
+
+DROP DATABASE mysqltest2;
+
+SELECT DATABASE(), @@collation_database;
+DATABASE()	@@collation_database
+NULL	latin1_swedish_ci
+
+EXECUTE stmt_c_1;
+DATABASE()	@@collation_database
+mysqltest1	utf8_unicode_ci
+
+SELECT DATABASE(), @@collation_database;
+DATABASE()	@@collation_database
+NULL	latin1_swedish_ci
+
+EXECUTE stmt_c_2;
+DATABASE()	@@collation_database
+NULL	latin1_swedish_ci
+Warnings:
+Note	1049	Unknown database 'mysqltest2'
+
+SELECT DATABASE(), @@collation_database;
+DATABASE()	@@collation_database
+NULL	latin1_swedish_ci
+
+PREPARE stmt_c_3 FROM 'SELECT DATABASE(), @@collation_database';
+
+EXECUTE stmt_c_3;
+DATABASE()	@@collation_database
+NULL	latin1_swedish_ci
+
+use mysqltest1;
+
+EXECUTE stmt_c_2;
+DATABASE()	@@collation_database
+NULL	latin1_swedish_ci
+Warnings:
+Note	1049	Unknown database 'mysqltest2'
+
+SELECT DATABASE(), @@collation_database;
+DATABASE()	@@collation_database
+mysqltest1	utf8_unicode_ci
+
+EXECUTE stmt_c_3;
+DATABASE()	@@collation_database
+NULL	latin1_swedish_ci
+
+SELECT DATABASE(), @@collation_database;
+DATABASE()	@@collation_database
+mysqltest1	utf8_unicode_ci
+
+DROP DATABASE mysqltest1;
+
+use test;
+
+########################################################################
 set @@global.query_cache_size=@initial_query_cache_size;
 flush status;

mysql-test/suite/rpl/r/rpl_ps.result

@@ -26,5 +26,44 @@ from-master-2-'',
 from-var-from-master-3
 drop table t1;
 stop slave;
+
+########################################################################
+#
+# BUG#25843: Changing default database between PREPARE and EXECUTE of
+# statement breaks binlog.
+#
+########################################################################
+
+#
+# Check that binlog is filled properly.
+#
+
+CREATE DATABASE mysqltest1;
+CREATE TABLE t1(c INT);
+
+RESET MASTER;
+RESET SLAVE;
+
+PREPARE stmt_d_1 FROM 'INSERT INTO t1 VALUES(1)';
+
+EXECUTE stmt_d_1;
+
+use mysqltest1;
+
+EXECUTE stmt_d_1;
+
+FLUSH LOGS;
+
+SHOW BINLOG EVENTS FROM 106;
+Log_name	Pos	Event_type	Server_id	End_log_pos	Info
+slave-bin.000001	106	Query	2	193	use `test`; INSERT INTO t1 VALUES(1)
+slave-bin.000001	193	Query	2	280	use `test`; INSERT INTO t1 VALUES(1)
+slave-bin.000001	280	Rotate	2	323	slave-bin.000002;pos=4
+
+DROP DATABASE mysqltest1;
+
+use test;
+
+########################################################################
 reset master;
 reset slave;

mysql-test/suite/rpl/t/rpl_ps.test

@@ -46,6 +46,74 @@ stop slave;
 
 # End of 4.1 tests
 
+#
+# Bug #25843 Changing default database between PREPARE and EXECUTE of statement
+# breaks binlog.
+#
+# There were actually two problems discovered by this bug:
+#
+#   1. Default (current) database is not fixed at the creation time.
+#      That leads to wrong output of DATABASE() function.
+#
+#   2. Database attributes (@@collation_database) are not fixed at the creation
+#      time. That leads to wrong resultset.
+#
+# Binlog breakage and Query Cache wrong output happened because of the first
+# problem.
+#
+
+--echo
+--echo ########################################################################
+--echo #
+--echo # BUG#25843: Changing default database between PREPARE and EXECUTE of
+--echo # statement breaks binlog.
+--echo #
+--echo ########################################################################
+
+###############################################################################
+
+--echo
+--echo #
+--echo # Check that binlog is filled properly.
+--echo #
+
+--echo
+CREATE DATABASE mysqltest1;
+CREATE TABLE t1(c INT);
+
+--echo
+RESET MASTER;
+RESET SLAVE;
+
+--echo
+PREPARE stmt_d_1 FROM 'INSERT INTO t1 VALUES(1)';
+
+--echo
+EXECUTE stmt_d_1;
+
+--echo
+use mysqltest1;
+
+--echo
+EXECUTE stmt_d_1;
+
+--echo
+FLUSH LOGS;
+
+--echo
+SHOW BINLOG EVENTS FROM 106;
+
+--echo
+DROP DATABASE mysqltest1;
+
+--echo
+use test;
+
+--echo
+--echo ########################################################################
+
+###############################################################################
+
 reset master;
 reset slave;
 disconnect master;

sql/mysql_priv.h

@@ -937,9 +937,16 @@ bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list, bool silent);
 bool do_rename(THD *thd, TABLE_LIST *ren_table, char *new_db,
                       char *new_table_name, char *new_table_alias,
                       bool skip_error);
+
 bool mysql_change_db(THD *thd, const LEX_STRING *new_db_name,
                      bool force_switch);
 
+bool mysql_opt_change_db(THD *thd,
+                         const LEX_STRING *new_db_name,
+                         LEX_STRING *saved_db_name,
+                         bool force_switch,
+                         bool *cur_db_changed);
+
 void mysql_parse(THD *thd, const char *inBuf, uint length,
                  const char ** semicolon);
 

sql/sp.cc

@@ -520,9 +520,10 @@ db_load_routine(THD *thd, int type, sp_name *name, sp_head **sphp,
 {
   LEX *old_lex= thd->lex, newlex;
   String defstr;
-  char old_db_buf[NAME_LEN+1];
-  LEX_STRING old_db= { old_db_buf, sizeof(old_db_buf) };
-  bool dbchanged;
+  char saved_cur_db_name_buf[NAME_LEN+1];
+  LEX_STRING saved_cur_db_name=
+    { saved_cur_db_name_buf, sizeof(saved_cur_db_name_buf) };
+  bool cur_db_changed;
   ulong old_sql_mode= thd->variables.sql_mode;
   ha_rows old_select_limit= thd->variables.select_limit;
   sp_rcontext *old_spcont= thd->spcont;
@@ -567,16 +568,16 @@ db_load_routine(THD *thd, int type, sp_name *name, sp_head **sphp,
   }
 
   /*
-    Change current database if needed.
+    Change the current database (if needed).
 
-    collation_database will be updated here. However, it can be wrong,
-    because it will contain the current value of the database collation.
-    We need collation_database to be fixed at the creation time -- so
-    we'll update it later in switch_query_ctx().
+    TODO: why do we force switch here?
   */
 
-  if ((ret= sp_use_new_db(thd, name->m_db, &old_db, TRUE, &dbchanged)))
+  if (mysql_opt_change_db(thd, &name->m_db, &saved_cur_db_name, TRUE,
+                          &cur_db_changed))
+  {
     goto end;
+  }
 
   thd->spcont= NULL;
 
@@ -585,34 +586,42 @@ db_load_routine(THD *thd, int type, sp_name *name, sp_head **sphp,
 
     lex_start(thd);
 
-    if (parse_sql(thd, &lip, creation_ctx) || newlex.sphead == NULL)
-    {
-      sp_head *sp= newlex.sphead;
+    ret= parse_sql(thd, &lip, creation_ctx) || newlex.sphead == NULL;
 
-      if (dbchanged && (ret= mysql_change_db(thd, &old_db, TRUE)))
-        goto end;
-      delete sp;
-      ret= SP_PARSE_ERROR;
+    /*
+      Force switching back to the saved current database (if changed),
+      because it may be NULL. In this case, mysql_change_db() would
+      generate an error.
+    */
+
+    if (cur_db_changed && mysql_change_db(thd, &saved_cur_db_name, TRUE))
+    {
+      delete newlex.sphead;
+      ret= -1;
+      goto end;
     }
-    else
+
+    if (ret)
     {
-      if (dbchanged && (ret= mysql_change_db(thd, &old_db, TRUE)))
-        goto end;
-      *sphp= newlex.sphead;
-      (*sphp)->set_definer(&definer_user_name, &definer_host_name);
-      (*sphp)->set_info(created, modified, &chistics, sql_mode);
-      (*sphp)->set_creation_ctx(creation_ctx);
-      (*sphp)->optimize();
-      /*
-        Not strictly necessary to invoke this method here, since we know
-        that we've parsed CREATE PROCEDURE/FUNCTION and not an
-        UPDATE/DELETE/INSERT/REPLACE/LOAD/CREATE TABLE, but we try to
-        maintain the invariant that this method is called for each
-        distinct statement, in case its logic is extended with other
-        types of analyses in future.
-      */
-      newlex.set_trg_event_type_for_tables();
+      delete newlex.sphead;
+      ret= SP_PARSE_ERROR;
+      goto end;
     }
+
+    *sphp= newlex.sphead;
+    (*sphp)->set_definer(&definer_user_name, &definer_host_name);
+    (*sphp)->set_info(created, modified, &chistics, sql_mode);
+    (*sphp)->set_creation_ctx(creation_ctx);
+    (*sphp)->optimize();
+    /*
+      Not strictly necessary to invoke this method here, since we know
+      that we've parsed CREATE PROCEDURE/FUNCTION and not an
+      UPDATE/DELETE/INSERT/REPLACE/LOAD/CREATE TABLE, but we try to
+      maintain the invariant that this method is called for each
+      distinct statement, in case its logic is extended with other
+      types of analyses in future.
+    */
+    newlex.set_trg_event_type_for_tables();
   }
 
 end:
@@ -2025,76 +2034,3 @@ create_string(THD *thd, String *buf,
   buf->append(body, bodylen);
   return TRUE;
 }
-
-
-
-/**
-  Change the current database if needed.
-
-  @param[in]      thd             thread handle
-  @param[in]      new_db          new database name
-  @param[in, out] old_db          IN: str points to a buffer where to store
-                                  the old database, length contains the
-                                  size of the buffer
-                                  OUT: if old db was not NULL, its name is
-                                  copied to the buffer pointed at by str
-                                  and length is updated accordingly.
-                                  Otherwise str[0] is set to '\0' and
-                                  length is set to 0. The out parameter
-                                  should be used only if the database name
-                                  has been changed (see dbchangedp).
-  @param[in]      force_switch    Flag to mysql_change_db(). For more information,
-                                  see mysql_change_db() comment.
-  @param[out]     dbchangedp      is set to TRUE if the current database is
-                                  changed, FALSE otherwise. The current
-                                  database is not changed if the old name
-                                  is equal to the new one, both names are
-                                  empty, or an error has occurred.
-
-  @return Operation status.
-    @retval 0 on success
-    @retval 1 access denied or out of memory
-              (the error message is set in THD)
-*/
-
-int
-sp_use_new_db(THD *thd,
-              LEX_STRING new_db,
-              LEX_STRING *old_db,
-              bool force_switch,
-              bool *dbchangedp)
-{
-  int ret;
-  DBUG_ENTER("sp_use_new_db");
-  DBUG_PRINT("enter", ("newdb: %s", new_db.str));
-
-  /*
-    A stored routine always belongs to some database. The
-    old database (old_db) might be NULL, but to restore the
-    old database we will use mysql_change_db.
-  */
-  DBUG_ASSERT(new_db.str && new_db.length);
-
-  if (thd->db)
-  {
-    old_db->length= (strmake(old_db->str, thd->db, old_db->length) -
-                     old_db->str);
-  }
-  else
-  {
-    old_db->str[0]= '\0';
-    old_db->length= 0;
-  }
-
-  /* Don't change the database if the new name is the same as the old one. */
-  if (my_strcasecmp(system_charset_info, old_db->str, new_db.str) == 0)
-  {
-    *dbchangedp= FALSE;
-    DBUG_RETURN(0);
-  }
-
-  ret= mysql_change_db(thd, &new_db, force_switch);
-
-  *dbchangedp= ret == 0;
-  DBUG_RETURN(ret);
-}

sql/sp.h

@@ -85,15 +85,4 @@ extern "C" uchar* sp_sroutine_key(const uchar *ptr, size_t *plen,
 */
 TABLE *open_proc_table_for_read(THD *thd, Open_tables_state *backup);
 
-
-/*
-  Do a "use new_db". The current db is stored at old_db.  If new_db is the
-  same as the current one, nothing is changed.  dbchangedp is set to true if
-  the db was actually changed.
-*/
-
-int
-sp_use_new_db(THD *thd, LEX_STRING new_db, LEX_STRING *old_db,
-	      bool no_access_check, bool *dbchangedp);
-
 #endif /* _SP_H_ */

sql/sp_head.cc

@@ -1016,9 +1016,10 @@ bool
 sp_head::execute(THD *thd)
 {
   DBUG_ENTER("sp_head::execute");
-  char old_db_buf[NAME_LEN+1];
-  LEX_STRING old_db= { old_db_buf, sizeof(old_db_buf) };
-  bool dbchanged;
+  char saved_cur_db_name_buf[NAME_LEN+1];
+  LEX_STRING saved_cur_db_name=
+    { saved_cur_db_name_buf, sizeof(saved_cur_db_name_buf) };
+  bool cur_db_changed= FALSE;
   sp_rcontext *ctx;
   bool err_status= FALSE;
   uint ip= 0;
@@ -1073,8 +1074,11 @@ sp_head::execute(THD *thd)
   */
 
   if (m_db.length &&
-      (err_status= sp_use_new_db(thd, m_db, &old_db, 0, &dbchanged)))
+      (err_status= mysql_opt_change_db(thd, &m_db, &saved_cur_db_name, FALSE,
+                                       &cur_db_changed)))
+  {
     goto done;
+  }
 
   if ((ctx= thd->spcont))
     ctx->clear_handler();
@@ -1255,14 +1259,14 @@ sp_head::execute(THD *thd)
     If the DB has changed, the pointer has changed too, but the
     original thd->db will then have been freed
   */
-  if (dbchanged)
+  if (cur_db_changed && !thd->killed)
   {
     /*
-      No access check when changing back to where we came from.
-      (It would generate an error from mysql_change_db() when old_db=="")
+      Force switching back to the saved current database, because it may be
+      NULL. In this case, mysql_change_db() would generate an error.
     */
-    if (! thd->killed)
-      err_status|= mysql_change_db(thd, &old_db, TRUE);
+
+    err_status|= mysql_change_db(thd, &saved_cur_db_name, TRUE);
   }
   m_flags&= ~IS_INVOKED;
   DBUG_PRINT("info",

sql/sql_class.cc

@@ -387,7 +387,6 @@ THD::THD()
   init_sql_alloc(&main_mem_root, ALLOC_ROOT_MIN_BLOCK_SIZE, 0);
   stmt_arena= this;
   thread_stack= 0;
-  db= 0;
   catalog= (char*)"std"; // the only catalog we have for now
   main_security_ctx.init();
   security_ctx= &main_security_ctx;
@@ -395,7 +394,7 @@ THD::THD()
   query_start_used= 0;
   count_cuted_fields= CHECK_FIELD_IGNORE;
   killed= NOT_KILLED;
-  db_length= col_access=0;
+  col_access=0;
   query_error= thread_specific_used= FALSE;
   hash_clear(&handler_tables_hash);
   tmp_table=0;
@@ -2040,7 +2039,9 @@ Statement::Statement(LEX *lex_arg, MEM_ROOT *mem_root_arg,
   lex(lex_arg),
   query(0),
   query_length(0),
-  cursor(0)
+  cursor(0),
+  db(NULL),
+  db_length(0)
 {
   name.str= NULL;
 }

sql/sql_class.h

@@ -593,6 +593,22 @@ public:
   uint32 query_length;                          // current query length
   Server_side_cursor *cursor;
 
+  /**
+    Name of the current (default) database.
+
+    If there is the current (default) database, "db" contains its name. If
+    there is no current (default) database, "db" is NULL and "db_length" is
+    0. In other words, "db", "db_length" must either be NULL, or contain a
+    valid database name.
+
+    @note this attribute is set and alloced by the slave SQL thread (for
+    the THD of that thread); that thread is (and must remain, for now) the
+    only responsible for freeing this member.
+  */
+
+  char *db;
+  uint db_length;
+
 public:
 
   /* This constructor is called for backup statements */
@@ -1024,18 +1040,21 @@ public:
   */
   char	  *thread_stack;
 
+  /**
+    Currently selected catalog.
+  */
+  char *catalog;
+
   /*
-    db - currently selected database
-    catalog - currently selected catalog
-    WARNING: some members of THD (currently 'db', 'catalog' and 'query')  are
-    set and alloced by the slave SQL thread (for the THD of that thread); that
-    thread is (and must remain, for now) the only responsible for freeing these
-    3 members. If you add members here, and you add code to set them in
-    replication, don't forget to free_them_and_set_them_to_0 in replication
-    properly. For details see the 'err:' label of the handle_slave_sql()
-    in sql/slave.cc.
-   */
-  char   *db, *catalog;
+    WARNING: some members of THD (currently 'Statement::db',
+    'catalog' and 'query')  are set and alloced by the slave SQL thread
+    (for the THD of that thread); that thread is (and must remain, for now)
+    the only responsible for freeing these 3 members. If you add members
+    here, and you add code to set them in replication, don't forget to
+    free_them_and_set_them_to_0 in replication properly. For details see
+    the 'err:' label of the handle_slave_sql() in sql/slave.cc.
+  */
+
   Security_context main_security_ctx;
   Security_context *security_ctx;
 
@@ -1390,7 +1409,6 @@ public:
   uint	     tmp_table, global_read_lock;
   uint	     server_status,open_options;
   enum enum_thread_type system_thread;
-  uint       db_length;
   uint       select_number;             //number of select (used for EXPLAIN)
   /* variables.transaction_isolation is reset to this after each commit */
   enum_tx_isolation session_tx_isolation;
@@ -1814,11 +1832,10 @@ public:
     no current database selected (in addition to the error message set by
     malloc).
 
-    @note This operation just sets {thd->db, thd->db_length}. Switching the
-    current database usually involves other actions, like switching other
-    database attributes including security context. In the future, this
-    operation will be made private and more convenient interface will be
-    provided.
+    @note This operation just sets {db, db_length}. Switching the current
+    database usually involves other actions, like switching other database
+    attributes including security context. In the future, this operation
+    will be made private and more convenient interface will be provided.
 
     @return Operation status
       @retval FALSE Success
@@ -1844,11 +1861,10 @@ public:
     @param new_db     a pointer to the new database name.
     @param new_db_len length of the new database name.
 
-    @note This operation just sets {thd->db, thd->db_length}. Switching the
-    current database usually involves other actions, like switching other
-    database attributes including security context. In the future, this
-    operation will be made private and more convenient interface will be
-    provided.
+    @note This operation just sets {db, db_length}. Switching the current
+    database usually involves other actions, like switching other database
+    attributes including security context. In the future, this operation
+    will be made private and more convenient interface will be provided.
   */
   void reset_db(char *new_db, size_t new_db_len)
   {

sql/sql_db.cc

@@ -1359,8 +1359,67 @@ static void mysql_change_db_impl(THD *thd,
 }
 
 
+
+/**
+  Backup the current database name before switch.
+
+  @param[in]      thd             thread handle
+  @param[in, out] saved_db_name   IN: "str" points to a buffer where to store
+                                  the old database name, "length" contains the
+                                  buffer size
+                                  OUT: if the current (default) database is
+                                  not NULL, its name is copied to the
+                                  buffer pointed at by "str"
+                                  and "length" is updated accordingly.
+                                  Otherwise "str" is set to NULL and
+                                  "length" is set to 0.
+*/
+
+static void backup_current_db_name(THD *thd,
+                                   LEX_STRING *saved_db_name)
+{
+  if (!thd->db)
+  {
+    /* No current (default) database selected. */
+
+    saved_db_name->str= NULL;
+    saved_db_name->length= 0;
+  }
+  else
+  {
+    strmake(saved_db_name->str, thd->db, saved_db_name->length);
+    saved_db_name->length= thd->db_length;
+  }
+}
+
+
+/**
+  Return TRUE if db1_name is equal to db2_name, FALSE otherwise.
+
+  The function allows to compare database names according to the MySQL
+  rules. The database names db1 and db2 are equal if:
+     - db1 is NULL and db2 is NULL;
+     or
+     - db1 is not-NULL, db2 is not-NULL, db1 is equal (ignoring case) to
+       db2 in system character set (UTF8).
+*/
+
+static inline bool
+cmp_db_names(const char *db1_name,
+             const char *db2_name)
+{
+  return
+         /* db1 is NULL and db2 is NULL */
+         !db1_name && !db2_name ||
+
+         /* db1 is not-NULL, db2 is not-NULL, db1 == db2. */
+         db1_name && db2_name &&
+         my_strcasecmp(system_charset_info, db1_name, db2_name) == 0;
+}
+
+
 /**
-  @brief Change the current database and its attributes.
+  @brief Change the current database and its attributes unconditionally.
 
   @param thd          thread handle
   @param new_db_name  database name
@@ -1577,6 +1636,43 @@ bool mysql_change_db(THD *thd, const LEX_STRING *new_db_name, bool force_switch)
 }
 
 
+/**
+  Change the current database and its attributes if needed.
+
+  @param          thd             thread handle
+  @param          new_db_name     database name
+  @param[in, out] saved_db_name   IN: "str" points to a buffer where to store
+                                  the old database name, "length" contains the
+                                  buffer size
+                                  OUT: if the current (default) database is
+                                  not NULL, its name is copied to the
+                                  buffer pointed at by "str"
+                                  and "length" is updated accordingly.
+                                  Otherwise "str" is set to NULL and
+                                  "length" is set to 0.
+  @param          force_switch    @see mysql_change_db()
+  @param[out]     cur_db_changed  out-flag to indicate whether the current
+                                  database has been changed (valid only if
+                                  the function suceeded)
+*/
+
+bool mysql_opt_change_db(THD *thd,
+                         const LEX_STRING *new_db_name,
+                         LEX_STRING *saved_db_name,
+                         bool force_switch,
+                         bool *cur_db_changed)
+{
+  *cur_db_changed= !cmp_db_names(thd->db, new_db_name->str);
+
+  if (!*cur_db_changed)
+    return FALSE;
+
+  backup_current_db_name(thd, saved_db_name);
+
+  return mysql_change_db(thd, new_db_name, force_switch);
+}
+
+
 static int
 lock_databases(THD *thd, const char *db1, uint length1,
                          const char *db2, uint length2)

sql/sql_prepare.cc

@@ -2868,6 +2868,19 @@ bool Prepared_statement::prepare(const char *packet, uint packet_len)
          init_param_array(this);
   lex->set_trg_event_type_for_tables();
 
+  /* Remember the current database. */
+
+  if (thd->db && thd->db_length)
+  {
+    db= this->strmake(thd->db, thd->db_length);
+    db_length= thd->db_length;
+  }
+  else
+  {
+    db= NULL;
+    db_length= 0;
+  }
+
   /*
     While doing context analysis of the query (in check_prepared_statement)
     we allocate a lot of additional memory: for open tables, JOINs, derived
@@ -2974,6 +2987,13 @@ bool Prepared_statement::execute(String *expanded_query, bool open_cursor)
   Query_arena *old_stmt_arena;
   bool error= TRUE;
 
+  char saved_cur_db_name_buf[NAME_LEN+1];
+  LEX_STRING saved_cur_db_name=
+    { saved_cur_db_name_buf, sizeof(saved_cur_db_name_buf) };
+  bool cur_db_changed;
+
+  LEX_STRING stmt_db_name= { db, db_length };
+
   status_var_increment(thd->status_var.com_stmt_execute);
 
   /* Check if we got an error when sending long data */
@@ -3022,6 +3042,21 @@ bool Prepared_statement::execute(String *expanded_query, bool open_cursor)
   */
 
   thd->set_n_backup_statement(this, &stmt_backup);
+
+  /*
+    Change the current database (if needed).
+
+    Force switching, because the database of the prepared statement may be
+    NULL (prepared statements can be created while no current database
+    selected).
+  */
+
+  if (mysql_opt_change_db(thd, &stmt_db_name, &saved_cur_db_name, TRUE,
+                          &cur_db_changed))
+    goto error;
+
+  /* Allocate query. */
+
   if (expanded_query->length() &&
       alloc_query(thd, (char*) expanded_query->ptr(),
                   expanded_query->length()+1))
@@ -3050,6 +3085,8 @@ bool Prepared_statement::execute(String *expanded_query, bool open_cursor)
 
   thd->protocol= protocol;                      /* activate stmt protocol */
 
+  /* Go! */
+
   if (open_cursor)
     error= mysql_open_cursor(thd, (uint) ALWAYS_MATERIALIZED_CURSOR,
                              &result, &cursor);
@@ -3068,6 +3105,17 @@ bool Prepared_statement::execute(String *expanded_query, bool open_cursor)
     }
   }
 
+  /*
+    Restore the current database (if changed).
+
+    Force switching back to the saved current database (if changed),
+    because it may be NULL. In this case, mysql_change_db() would generate
+    an error.
+  */
+
+  if (cur_db_changed)
+    mysql_change_db(thd, &saved_cur_db_name, TRUE);
+
   thd->protocol= &thd->protocol_text;         /* use normal protocol */
 
   /* Assert that if an error, no cursor is open */