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Bug#54488 crash when using explain and prepared statements with subqueries

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The crash happens because original join table is replaced with temporary table
at execution stage and later we attempt to use this temporary table in
select_describe. It might happen that
Item_subselect::update_used_tables() method which sets const_item flag
is not called by some reasons (no where/having conditon in subquery for example).
It prevents JOIN::join_tmp creation and breaks original join.
The fix is to call ::update_used_tables() before ::const_item() check.


mysql-test/r/ps.result:
  test case
mysql-test/t/ps.test:
  test case
sql/item_subselect.cc:
  call ::update_used_tables() before ::const_item() check.
This commit is contained in:
Sergey Glukhov 2010-10-01 14:08:38 +04:00
parent b76277fce5
commit 233e4d809a
3 changed files with 44 additions and 11 deletions
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18
mysql-test/r/ps.result
View File

@ -3021,4 +3021,22 @@ Warnings:
Note 1003 select 1 AS `1` from `test`.`t1` `t2` left join `test`.`t1` on(1) where 1
DEALLOCATE PREPARE stmt;
DROP TABLE t1;
#
# Bug#54488 crash when using explain and prepared statements with subqueries
#
CREATE TABLE t1(f1 INT);
INSERT INTO t1 VALUES (1),(1);
PREPARE stmt FROM 'EXPLAIN SELECT 1 FROM t1 WHERE (SELECT (SELECT 1 FROM t1 GROUP BY f1))';
EXECUTE stmt;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2
2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL No tables used
3 SUBQUERY t1 ALL NULL NULL NULL NULL 2 Using temporary; Using filesort
EXECUTE stmt;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2
2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL No tables used
3 SUBQUERY t1 ALL NULL NULL NULL NULL 2 Using temporary; Using filesort
DEALLOCATE PREPARE stmt;
DROP TABLE t1;
End of 5.1 tests.

11
mysql-test/t/ps.test
View File

@ -3090,4 +3090,15 @@ EXECUTE stmt;
DEALLOCATE PREPARE stmt;
DROP TABLE t1;
--echo #
--echo # Bug#54488 crash when using explain and prepared statements with subqueries
--echo #
CREATE TABLE t1(f1 INT);
INSERT INTO t1 VALUES (1),(1);
PREPARE stmt FROM 'EXPLAIN SELECT 1 FROM t1 WHERE (SELECT (SELECT 1 FROM t1 GROUP BY f1))';
EXECUTE stmt;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
DROP TABLE t1;
--echo End of 5.1 tests.

26
sql/item_subselect.cc
View File

@ -1914,18 +1914,22 @@ int subselect_single_select_engine::exec()
}
if (!select_lex->uncacheable && thd->lex->describe &&
!(join->select_options & SELECT_DESCRIBE) &&
join->need_tmp && item->const_item())
join->need_tmp)
{
/*
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())
DBUG_RETURN(1); /* purecov: inspected */
item->update_used_tables();
if (item->const_item())
{
/*
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())
DBUG_RETURN(1); /* purecov: inspected */
}
}
if (item->engine_changed)
{