Merge macbook.local:/Users/kgeorge/mysql/work/mysql-5.0-opt

into  macbook.local:/Users/kgeorge/mysql/work/merge-5.1-opt


mysql-test/r/distinct.result:
  Auto merged
mysql-test/r/gis-rtree.result:
  Auto merged
mysql-test/r/ps.result:
  Auto merged
mysql-test/r/subselect.result:
  Auto merged
mysql-test/r/udf.result:
  Auto merged
mysql-test/t/gis-rtree.test:
  Auto merged
mysql-test/t/ps.test:
  Auto merged
mysql-test/t/subselect.test:
  Auto merged
mysql-test/t/udf.test:
  Auto merged
sql/item_subselect.cc:
  Auto merged
sql/item_subselect.h:
  Auto merged
sql/sql_lex.cc:
  Auto merged
sql/sql_select.cc:
  Auto merged
storage/myisam/mi_check.c:
  Auto merged
sql/sql_udf.cc:
  SCCS merged

1 files changed, 17 insertions, 2 deletions

diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc
index 0074e33cdea..f3f840bdaa9 100644
--- a/sql/item_subselect.cc
+++ b/sql/item_subselect.cc
@@ -391,6 +391,7 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
       */
       !(select_lex->item_list.head()->type() == FIELD_ITEM ||
 	select_lex->item_list.head()->type() == REF_ITEM) &&
+      !join->conds && !join->having &&
       /*
         switch off this optimization for prepare statement,
         because we do not rollback this changes
@@ -415,8 +416,6 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
     */
     substitution->walk(&Item::remove_dependence_processor, 0,
 		       (byte *) select_lex->outer_select());
-    /* SELECT without FROM clause can't have WHERE or HAVING clause */
-    DBUG_ASSERT(join->conds == 0 && join->having == 0);
     return RES_REDUCE;
   }
   return RES_OK;
@@ -2320,6 +2319,22 @@ bool subselect_single_select_engine::no_tables()
 
 
 /*
+  Check statically whether the subquery can return NULL
+
+  SINOPSYS
+    subselect_single_select_engine::may_be_null()
+
+  RETURN
+    FALSE  can guarantee that the subquery never return NULL
+    TRUE   otherwise
+*/
+bool subselect_single_select_engine::may_be_null()
+{
+  return ((no_tables() && !join->conds && !join->having) ? maybe_null : 1);
+}
+
+
+/*
   Report about presence of tables in subquery
 
   SYNOPSIS