Fix for bug #9486 "Can't perform multi-update in stored procedure".

New more SP-locking friendly approach to handling locks in multi-update.
Now we mark all tables of multi-update as needing write lock at parsing
stage and if possible downgrade lock at execution stage (For its work
SP-locking mechanism needs to know all lock types right after parsing
stage).

mysql-test/r/sp-threads.result

@@ -23,3 +23,20 @@ select * from t1;
 s1	s2	s3
 drop table t1;
 drop procedure bug4934;
+drop procedure if exists bug9486;
+drop table if exists t1, t2;
+create table t1 (id1 int, val int);
+create table t2 (id2 int);
+create procedure bug9486()
+update t1, t2 set val= 1 where id1=id2;
+call bug9486();
+lock tables t2 write;
+ call bug9486();
+show processlist;
+Id	User	Host	db	Command	Time	State	Info
+#	root	localhost	test	Sleep	#		NULL
+#	root	localhost	test	Query	#	Locked	call bug9486()
+#	root	localhost	test	Query	#	NULL	show processlist
+unlock tables;
+drop procedure bug9486;
+drop table t1, t2;

mysql-test/t/sp-threads.test

@@ -54,6 +54,37 @@ drop table t1;
 drop procedure bug4934;
 
 
+#
+# BUG #9486 "Can't perform multi-update in stored procedure"
+#
+--disable_warnings
+drop procedure if exists bug9486;
+drop table if exists t1, t2;
+--enable_warnings
+create table t1 (id1 int, val int);
+create table t2 (id2 int);
+
+create procedure bug9486()
+  update t1, t2 set val= 1 where id1=id2;
+call bug9486();
+# Let us check that SP invocation requires write lock for t2.
+connection con2root;
+lock tables t2 write;
+connection con1root;
+send call bug9486();
+connection con2root;
+--sleep 2
+# There should be call statement in locked state.
+--replace_column 1 # 6 #
+show processlist;
+unlock tables;
+connection con1root;
+reap;
+
+drop procedure bug9486;
+drop table t1, t2;
+
+
 #
 # BUG#NNNN: New bug synopsis
 #

sql/sp_head.cc

@@ -2026,6 +2026,12 @@ typedef struct st_sp_table
   LEX_STRING qname;
   bool temp;
   TABLE_LIST *table;
+  /*
+    We can't use table->lock_type as lock type for table
+    in multi-set since it can be changed by statement during
+    its execution (e.g. as this happens for multi-update).
+  */
+  thr_lock_type lock_type;
   uint lock_count;
   uint query_lock_count;
 } SP_TABLE;
@@ -2097,8 +2103,8 @@ sp_head::merge_table_list(THD *thd, TABLE_LIST *table, LEX *lex_for_tmp_check)
       */
       if ((tab= (SP_TABLE *)hash_search(&m_sptabs, (byte *)tname, tlen)))
       {
-	if (tab->table->lock_type < table->lock_type)
-	  tab->table= table;	// Use the table with the highest lock type
+        if (tab->lock_type < table->lock_type)
+          tab->lock_type= table->lock_type; // Use the table with the highest lock type
         tab->query_lock_count++;
         if (tab->query_lock_count > tab->lock_count)
           tab->lock_count++;
@@ -2116,6 +2122,7 @@ sp_head::merge_table_list(THD *thd, TABLE_LIST *table, LEX *lex_for_tmp_check)
 	    lex_for_tmp_check->create_info.options & HA_LEX_CREATE_TMP_TABLE)
 	  tab->temp= TRUE;
 	tab->table= table;
+        tab->lock_type= table->lock_type;
         tab->lock_count= tab->query_lock_count= 1;
 	my_hash_insert(&m_sptabs, (byte *)tab);
       }
@@ -2188,7 +2195,7 @@ sp_head::add_used_tables_to_table_list(THD *thd,
       table->alias= otable->alias;
       table->table_name= otable->table_name;
       table->table_name_length= otable->table_name_length;
-      table->lock_type= otable->lock_type;
+      table->lock_type= stab->lock_type;
       table->cacheable_table= 1;
       table->prelocking_placeholder= 1;
 

sql/sql_lex.h

@@ -732,7 +732,7 @@ typedef struct st_lex
   USER_RESOURCES mqh;
   ulong type;
   enum_sql_command sql_command, orig_sql_command;
-  thr_lock_type lock_option, multi_lock_option;
+  thr_lock_type lock_option;
   enum SSL_type ssl_type;			/* defined in violite.h */
   enum my_lex_states next_state;
   enum enum_duplicates duplicates;

sql/sql_prepare.cc

@@ -1012,11 +1012,6 @@ static int mysql_test_update(Prepared_statement *stmt,
       DBUG_PRINT("info", ("Switch to multi-update"));
       /* pass counter value */
       thd->lex->table_count= table_count;
-      /*
-	give correct value to multi_lock_option, because it will be used
-	in multiupdate
-      */
-      thd->lex->multi_lock_option= table_list->lock_type;
       /* convert to multiupdate */
       return 2;
     }

sql/sql_update.cc

@@ -145,11 +145,6 @@ int mysql_update(THD *thd,
     DBUG_PRINT("info", ("Switch to multi-update"));
     /* pass counter value */
     thd->lex->table_count= table_count;
-    /*
-      give correct value to multi_lock_option, because it will be used
-      in multiupdate
-    */
-    thd->lex->multi_lock_option= table_list->lock_type;
     /* convert to multiupdate */
     return 2;
   }
@@ -692,8 +687,10 @@ bool mysql_multi_update_prepare(THD *thd)
       }
 
       DBUG_PRINT("info",("setting table `%s` for update", tl->alias));
-      tl->lock_type= lex->multi_lock_option;
-      tl->updating= 1;
+      /*
+        If table will be updated we should not downgrade lock for it and
+        leave it as is.
+      */
     }
     else
     {
@@ -705,15 +702,15 @@ bool mysql_multi_update_prepare(THD *thd)
       */
       tl->lock_type= using_update_log ? TL_READ_NO_INSERT : TL_READ;
       tl->updating= 0;
+      /* Update TABLE::lock_type accordingly. */
+      if (!tl->placeholder() && !tl->schema_table && !using_lock_tables)
+        tl->table->reginfo.lock_type= tl->lock_type;
     }
 
     /* Check access privileges for table */
     if (!tl->derived && !tl->belong_to_view)
     {
       uint want_privilege= tl->updating ? UPDATE_ACL : SELECT_ACL;
-      if (!using_lock_tables)
-        tl->table->reginfo.lock_type= tl->lock_type;
-
       if (check_access(thd, want_privilege,
                         tl->db, &tl->grant.privilege, 0, 0) ||
           (grant_option && check_grant(thd, want_privilege, tl, 0, 1, 0)))
@@ -847,7 +844,7 @@ bool mysql_multi_update(THD *thd,
                       result, unit, select_lex);
   delete result;
   thd->abort_on_warning= 0;
-  DBUG_RETURN(TRUE);
+  DBUG_RETURN(FALSE);
 }
 
 

sql/sql_yacc.yy

@@ -5969,10 +5969,7 @@ update:
 	{
 	  LEX *lex= Lex;
           if (lex->select_lex.table_list.elements > 1)
-	  {
             lex->sql_command= SQLCOM_UPDATE_MULTI;
-	    lex->multi_lock_option= $3;
-	  }
 	  else if (lex->select_lex.get_table_list()->derived)
 	  {
 	    /* it is single table update and it is update of derived table */
@@ -5980,8 +5977,12 @@ update:
                      lex->select_lex.get_table_list()->alias, "UPDATE");
 	    YYABORT;
 	  }
-	  else
-	    Select->set_lock_for_tables($3);
+          /*
+            In case of multi-update setting write lock for all tables may
+            be too pessimistic. We will decrease lock level if possible in
+            mysql_multi_update().
+          */
+          Select->set_lock_for_tables($3);
 	}
 	where_clause opt_order_clause delete_limit_clause {}
 	;