Bug#29936 (Stored Procedure DML ignores low_priority_updates setting)

This is a follow up for the patch for Bug#26162 "Trigger DML ignores low_priority_updates setting", where the stored procedure ignores the session setting of low_priority_updates.

For every table open operation with default write (TL_WRITE_DEFAULT) lock_type, downgrade the lock type to the session setting of low_priority_updates.

sql/lock.cc

@@ -730,6 +730,7 @@ static MYSQL_LOCK *get_lock_data(THD *thd, TABLE **table_ptr, uint count,
     if ((table=table_ptr[i])->s->tmp_table == NON_TRANSACTIONAL_TMP_TABLE)
       continue;
     lock_type= table->reginfo.lock_type;
+    DBUG_ASSERT (lock_type != TL_WRITE_DEFAULT);
     if (lock_type >= TL_WRITE_ALLOW_WRITE)
     {
       *write_lock_used=table;

sql/sql_base.cc

@@ -1537,7 +1537,6 @@ TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
   HASH_SEARCH_STATE state;
   DBUG_ENTER("open_table");
 
-  DBUG_ASSERT (table_list->lock_type != TL_WRITE_DEFAULT);
   /* find a unused table in the open table cache */
   if (refresh)
     *refresh=0;
@@ -2708,11 +2707,6 @@ int open_tables(THD *thd, TABLE_LIST **start, uint *counter, uint flags)
   {
     safe_to_ignore_table= FALSE;
 
-    if (tables->lock_type == TL_WRITE_DEFAULT)
-    {
-      tables->lock_type= thd->update_lock_default;
-      DBUG_ASSERT (tables->lock_type >= TL_WRITE_ALLOW_WRITE);
-    }
     /*
       Ignore placeholders for derived tables. After derived tables
       processing, link to created temporary table will be put here.
@@ -2857,7 +2851,8 @@ int open_tables(THD *thd, TABLE_LIST **start, uint *counter, uint flags)
     }
 
     if (tables->lock_type != TL_UNLOCK && ! thd->locked_tables)
-      tables->table->reginfo.lock_type=tables->lock_type;
+      tables->table->reginfo.lock_type= tables->lock_type == TL_WRITE_DEFAULT ?
+        thd->update_lock_default : tables->lock_type;
     tables->table->grant= tables->grant;
 
 process_view_routines: