Fix for BUG#25843: changing default database between PREPARE and EXECUTE

of statement breaks binlog.

There were 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.

The fix is to remember the current database at the PREPARE-time and
set it each time at EXECUTE.


mysql-test/include/query_cache_sql_prepare.inc:
  The first part of the test case for BUG#25843.
mysql-test/r/query_cache_ps_no_prot.result:
  Update result file.
mysql-test/r/query_cache_ps_ps_prot.result:
  Update result file.
mysql-test/suite/rpl/r/rpl_ps.result:
  Update result file.
mysql-test/suite/rpl/t/rpl_ps.test:
  The second part of the test case for BUG#25843.
sql/mysql_priv.h:
  Added mysql_opt_change_db() prototype.
sql/sp.cc:
  1. Polishing;
  2. sp_use_new_db() has been removed;
  3. Use mysql_opt_change_db() instead of sp_use_new_db().
sql/sp.h:
  sp_use_new_db() has been removed.
  This function has nothing to do with a) sp and b) *new* database.
  It was merely "switch the current database if needed".
sql/sp_head.cc:
  1. Polishing.
  2. Use mysql_opt_change_db() instead of sp_use_new_db().
sql/sql_class.cc:
  Move THD::{db, db_length} into Statement.
sql/sql_class.h:
  Move THD::{db, db_length} into Statement.
sql/sql_db.cc:
  Introduce mysql_opt_change_db() as a replacement (and inspired by)
  sp_use_new_db().
sql/sql_prepare.cc:
  1. Remember the current database in Prepared_statement::prepare().
  2. Switch/restore the current database in Prepared_statement::execute().

1 files changed, 42 insertions, 106 deletions

diff --git a/sql/sp.cc b/sql/sp.cc
index 8655e520041..e910bd6443d 100644
--- a/sql/sp.cc
+++ b/sql/sp.cc
@@ -519,9 +519,10 @@ 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;
@@ -566,16 +567,16 @@ 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;
 
@@ -584,34 +585,42 @@ 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:
@@ -2024,76 +2033,3 @@ 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);
-}