diff options
Diffstat (limited to 'sql/item_subselect.cc')
| -rw-r--r-- | sql/item_subselect.cc | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc index cd854f012a8..2164d5ae070 100644 --- a/sql/item_subselect.cc +++ b/sql/item_subselect.cc @@ -1935,21 +1935,26 @@ int subselect_single_select_engine::exec() DBUG_RETURN(join->error ? join->error : 1); } if (!select_lex->uncacheable && thd->lex->describe && - !(join->select_options & SELECT_DESCRIBE) && - join->need_tmp) + !(join->select_options & SELECT_DESCRIBE)) { item->update_used_tables(); if (item->const_item()) { /* + It's necessary to keep original JOIN table because + create_sort_index() function may overwrite original + JOIN_TAB::type and wrong optimization method can be + selected on re-execution. + */ + select_lex->uncacheable|= UNCACHEABLE_EXPLAIN; + select_lex->master_unit()->uncacheable|= UNCACHEABLE_EXPLAIN; + /* Force join->join_tmp creation, because this subquery will be replaced by a simple select from the materialization temp table by optimize() called by EXPLAIN and we need to preserve the initial query structure so we can display it. */ - select_lex->uncacheable|= UNCACHEABLE_EXPLAIN; - select_lex->master_unit()->uncacheable|= UNCACHEABLE_EXPLAIN; - if (join->init_save_join_tab()) + if (join->need_tmp && join->init_save_join_tab()) DBUG_RETURN(1); /* purecov: inspected */ } } |