BUG#5390 - problems with merge tables

Additional fix for INSERT DELAYED with subselect.
Originally detected in 5.1, but 5.0 could also be affected.
The user thread creates a dummy table object,
which is not included in the lock. The 'real' table is
opened and locked by the 'delayed' system thread.
The dummy object is now marked as not locked and this is
tested in mysql_lock_have_duplicate().

sql/lock.cc

@@ -530,8 +530,11 @@ TABLE_LIST *mysql_lock_have_duplicate(THD *thd, TABLE_LIST *needle,
   THR_LOCK_DATA         **end_data2;
   DBUG_ENTER("mysql_lock_have_duplicate");
 
-  /* Table may not be defined for derived or view tables. */
-  if (! (table= needle->table))
+  /*
+    Table may not be defined for derived or view tables.
+    Table may not be part of a lock for delayed operations.
+  */
+  if (! (table= needle->table) || ! table->lock_count)
     goto end;
 
   /* A temporary table does not have locks. */
@@ -550,7 +553,8 @@ TABLE_LIST *mysql_lock_have_duplicate(THD *thd, TABLE_LIST *needle,
   lock_tables= mylock->table;
 
   /* Prepare table related variables that don't change in loop. */
-  DBUG_ASSERT(table == lock_tables[table->lock_position]);
+  DBUG_ASSERT((table->lock_position < mylock->table_count) &&
+              (table == lock_tables[table->lock_position]));
   table_lock_data= lock_locks + table->lock_data_start;
   end_data= table_lock_data + table->lock_count;
 
@@ -563,7 +567,8 @@ TABLE_LIST *mysql_lock_have_duplicate(THD *thd, TABLE_LIST *needle,
       continue;
 
     /* All tables in list must be in lock. */
-    DBUG_ASSERT(table2 == lock_tables[table2->lock_position]);
+    DBUG_ASSERT((table2->lock_position < mylock->table_count) &&
+                (table2 == lock_tables[table2->lock_position]));
 
     for (lock_data2=  lock_locks + table2->lock_data_start,
            end_data2= lock_data2 + table2->lock_count;

sql/sql_insert.cc

@@ -1536,7 +1536,10 @@ TABLE *delayed_insert::get_local_table(THD* client_thd)
 
   /* Adjust in_use for pointing to client thread */
   copy->in_use= client_thd;
-  
+
+  /* Adjust lock_count. This table object is not part of a lock. */
+  copy->lock_count= 0;
+
   return copy;
 
   /* Got fatal error */