diff options
Diffstat (limited to 'sql')
| -rw-r--r-- | sql/item_subselect.h | 4 | ||||
| -rw-r--r-- | sql/sql_union.cc | 19 | ||||
| -rw-r--r-- | sql/table.h | 13 |
3 files changed, 33 insertions, 3 deletions
diff --git a/sql/item_subselect.h b/sql/item_subselect.h index 23bdeacade9..816073ed5d3 100644 --- a/sql/item_subselect.h +++ b/sql/item_subselect.h @@ -145,6 +145,10 @@ public: Item_subselect(THD *thd); virtual subs_type substype() { return UNKNOWN_SUBS; } + bool is_exists_predicate() + { + return substype() == Item_subselect::EXISTS_SUBS; + } bool is_in_predicate() { return (substype() == Item_subselect::IN_SUBS || diff --git a/sql/sql_union.cc b/sql/sql_union.cc index b2198eb2b31..8b1719c60cb 100644 --- a/sql/sql_union.cc +++ b/sql/sql_union.cc @@ -514,6 +514,25 @@ bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result, found_rows_for_union= first_sl->options & OPTION_FOUND_ROWS; is_union_select= is_union() || fake_select_lex; + /* + If we are reading UNION output and the UNION is in the + IN/ANY/ALL/EXISTS subquery, then ORDER BY is redundant and hence should + be removed. + Example: + select ... col IN (select col2 FROM t1 union select col3 from t2 ORDER BY 1) + + (as for ORDER BY ... LIMIT, it currently not supported inside + IN/ALL/ANY subqueries) + (For non-UNION this removal of ORDER BY clause is done in + check_and_do_in_subquery_rewrites()) + */ + if (is_union() && item && + (item->is_in_predicate() || item->is_exists_predicate())) + { + global_parameters()->order_list.first= NULL; + global_parameters()->order_list.elements= 0; + } + /* Global option */ if (is_union_select || is_recursive) diff --git a/sql/table.h b/sql/table.h index f3a7f278604..14ab0027a79 100644 --- a/sql/table.h +++ b/sql/table.h @@ -1281,9 +1281,16 @@ public: /* number of select if it is derived table */ uint derived_select_number; /* - 0 or JOIN_TYPE_{LEFT|RIGHT}. Currently this is only compared to 0. - If maybe_null !=0, this table is inner w.r.t. some outer join operation, - and null_row may be true. + Possible values: + - 0 by default + - JOIN_TYPE_{LEFT|RIGHT} if the table is inner w.r.t an outer join + operation + - 1 if the SELECT has mixed_implicit_grouping=1. example: + select max(col1), col2 from t1. In this case, the query produces + one row with all columns having NULL values. + + Interpetation: If maybe_null!=0, all fields of the table are considered + NULLable (and have NULL values when null_row=true) */ uint maybe_null; int current_lock; /* Type of lock on table */ |