Merge bk-internal:/home/bk/mysql-4.1/

into serg.mylan:/usr/home/serg/Abk/mysql-4.1

sql/sql_union.cc

@@ -355,15 +355,18 @@ int st_select_lex_unit::exec()
   
   if (uncacheable || !item || !item->assigned() || describe)
   {
-    if (optimized && item && item->assigned())
+    if (optimized && item)
+    {
+      if (item->assigned())
       {
         item->assigned(0); // We will reinit & rexecute unit
         item->reset();
         table->file->delete_all_rows();
       }
-    if (union_distinct && table->file->enable_indexes(HA_KEY_SWITCH_ALL) &&
-        !describe)
-      DBUG_RETURN(1);  // For sub-selects
+      /* re-enabling indexes for next subselect iteration */
+      if (union_distinct && table->file->enable_indexes(HA_KEY_SWITCH_ALL))
+        DBUG_ASSERT(1);
+    }
     for (SELECT_LEX *sl= select_cursor; sl; sl= sl->next_select())
     {
       ha_rows records_at_start= 0;