Commit df3341a7 authored by gkodinov/kgeorge@magare.gmz's avatar gkodinov/kgeorge@magare.gmz
Browse files

Bug #36011: server crash with explain extended on query 

   with dependent subqueries
An IN subquery is executed on EXPLAIN when it's not correlated.
If the subquery required a temporary table for its execution
not all the internal structures were restored from pointing to
the items of the temporary table to point back to the items of
the subquery.
Fixed by restoring the ref array when a temp tables were used in
executing the IN subquery during EXPLAIN EXTENDED.
parent c86fc51e

mysql-test/r/subselect.result

+15 −0
Original line number Diff line number Diff line
@@ -4381,4 +4381,19 @@ t1.a= (select b from t2 limit 1) and not 
t1.a= (select a from t2 limit 1) ;

a

drop table t1, t2;

CREATE TABLE t1 (a INT);

INSERT INTO t1 VALUES (1),(2);

EXPLAIN EXTENDED SELECT 1 FROM t1 WHERE 1 IN (SELECT 1 FROM t1 GROUP BY a);

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	

2	DEPENDENT SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	Using temporary; Using filesort

Warnings:

Note	1003	select 1 AS `1` from `test`.`t1` where <in_optimizer>(1,<exists>(select 1 AS `1` from `test`.`t1` group by `test`.`t1`.`a` having (<cache>(1) = <ref_null_helper>(1))))

EXPLAIN EXTENDED SELECT 1 FROM t1 WHERE 1 IN (SELECT 1 FROM t1 WHERE a > 3 GROUP BY a);

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables

2	DEPENDENT SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	Using where; Using temporary; Using filesort

Warnings:

Note	1003	select 1 AS `1` from `test`.`t1` where <in_optimizer>(1,<exists>(select 1 AS `1` from `test`.`t1` where (`test`.`t1`.`a` > 3) group by `test`.`t1`.`a` having (<cache>(1) = <ref_null_helper>(1))))

DROP TABLE t1;

End of 5.0 tests.

mysql-test/t/subselect.test

+11 −0
Original line number Diff line number Diff line
@@ -3271,5 +3271,16 @@ select t1.a from t1 where 


drop table t1, t2;



#

# Bug #36011: Server crash with explain extended on query with dependent

# subqueries

#



CREATE TABLE t1 (a INT);

INSERT INTO t1 VALUES (1),(2);

EXPLAIN EXTENDED SELECT 1 FROM t1 WHERE 1 IN (SELECT 1 FROM t1 GROUP BY a);

EXPLAIN EXTENDED SELECT 1 FROM t1 WHERE 1 IN (SELECT 1 FROM t1 WHERE a > 3 GROUP BY a);

DROP TABLE t1;



--echo End of 5.0 tests.

sql/sql_select.cc

+5 −4
Original line number Diff line number Diff line
@@ -2104,11 +2104,12 @@ JOIN::exec() 
  /* 

    With EXPLAIN EXTENDED we have to restore original ref_array

    for a derived table which is always materialized.

    We also need to do this when we have temp table(s).

    Otherwise we would not be able to print the query correctly.

  */ 

  if (items0 &&

      (thd->lex->describe & DESCRIBE_EXTENDED) &&

      select_lex->linkage == DERIVED_TABLE_TYPE)      

  if (items0 && (thd->lex->describe & DESCRIBE_EXTENDED) &&

      (select_lex->linkage == DERIVED_TABLE_TYPE ||

       exec_tmp_table1 || exec_tmp_table2))

    set_items_ref_array(items0);



  DBUG_VOID_RETURN;