diff options
Diffstat (limited to 'sql/item_subselect.cc')
| -rw-r--r-- | sql/item_subselect.cc | 31 |
1 files changed, 25 insertions, 6 deletions
diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc index aaf2aa60fc6..5a1a8c7ee68 100644 --- a/sql/item_subselect.cc +++ b/sql/item_subselect.cc @@ -2906,7 +2906,6 @@ bool Item_exists_subselect::exists2in_processor(void *opt_arg) !upper_not->is_top_level_item())) || first_select->is_part_of_union() || first_select->group_list.elements || - first_select->order_list.elements || join->having || first_select->with_sum_func || !first_select->leaf_tables.elements|| @@ -2914,8 +2913,31 @@ bool Item_exists_subselect::exists2in_processor(void *opt_arg) with_recursive_reference) DBUG_RETURN(FALSE); - DBUG_ASSERT(first_select->order_list.elements == 0 && - first_select->group_list.elements == 0 && + /* + EXISTS-to-IN coversion and ORDER BY ... LIMIT clause: + + - "[ORDER BY ...] LIMIT n" clause with a non-zero n does not affect + the result of the EXISTS(...) predicate, and so we can discard + it during the conversion. + - "[ORDER BY ...] LIMIT m, n" can turn a non-empty resultset into empty + one, so it affects tthe EXISTS(...) result and cannot be discarded. + + Disallow exists-to-in conversion if + (1). three is a LIMIT which is not a basic constant + (1a) or is a "LIMIT 0" (see MDEV-19429) + (2). there is an OFFSET clause + */ + if ((first_select->select_limit && // (1) + (!first_select->select_limit->basic_const_item() || // (1) + first_select->select_limit->val_uint() == 0)) || // (1a) + first_select->offset_limit) // (2) + { + DBUG_RETURN(FALSE); + } + + /* Disallow the conversion if offset + limit exists */ + + DBUG_ASSERT(first_select->group_list.elements == 0 && first_select->having == NULL); if (find_inner_outer_equalities(&join->conds, eqs)) @@ -2946,9 +2968,6 @@ bool Item_exists_subselect::exists2in_processor(void *opt_arg) if ((uint)eqs.elements() > (first_select->item_list.elements + first_select->select_n_reserved)) goto out; - /* It is simple query */ - DBUG_ASSERT(first_select->join->all_fields.elements == - first_select->item_list.elements); arena= thd->activate_stmt_arena_if_needed(&backup); |