diff options
Diffstat (limited to 'sql/item_subselect.cc')
| -rw-r--r-- | sql/item_subselect.cc | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc index cd1f8f83821..20a092d7607 100644 --- a/sql/item_subselect.cc +++ b/sql/item_subselect.cc @@ -350,6 +350,7 @@ 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 optimisation for prepare statement, because we do not rollback this changes @@ -374,8 +375,6 @@ Item_singlerow_subselect::select_transformer(JOIN *join) */ substitution->walk(&Item::remove_dependence_processor, (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; @@ -1796,6 +1795,22 @@ 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 SINOPSYS |