Valgrind warnings (blocks are definitely lost) in filesort on IN subquery with SUM and DISTINCT

==2176== 216 bytes in 1 blocks are definitely lost in loss record 2 of 3

==2176==    at 0x4C28F9F: malloc (vg_replace_malloc.c:236)

==2176==    by 0xCDB465: my_malloc (my_malloc.c:41)

==2176==    by 0x7CAD24: filesort(THD*, TABLE*, st_sort_field*, unsigned int, SQL_SELECT*, unsigned long long, bool, unsigned long long*) (filesort.cc:211)

==2176==    by 0x66FAD1: create_sort_index(THD*, JOIN*, st_order*, unsigned long long, unsigned long long, bool) (sql_select.cc:19020)

==2176==    by 0x6485B6: JOIN::exec() (sql_select.cc:2803)

==2176==    by 0x86BD33: subselect_single_select_engine::exec() (item_subselect.cc:3205)

==2176==    by 0x8648B5: Item_subselect::exec() (item_subselect.cc:644)

==2176==    by 0x864DCF: Item_in_subselect::exec() (item_subselect.cc:817)

==2176==    by 0x8671F6: Item_in_subselect::val_bool() (item_subselect.cc:1638)

==2176==    by 0x575060: Item::val_bool_result() (item.h:963)

==2176==    by 0x803D34: Item_in_optimizer::val_int() (item_cmpfunc.cc:1736)

==2176==    by 0x829A70: eval_const_cond(Item*) (item_func.cc:80)

==2176==    by 0x661A73: internal_remove_eq_conds(THD*, Item*, Item::cond_result*) (sql_select.cc:13442)

==2176==    by 0x661DB7: remove_eq_conds(THD*, Item*, Item::cond_result*) (sql_select.cc:13534)

==2176==    by 0x661440: optimize_cond(JOIN*, Item*, List<TABLE_LIST>*, Item::cond_result*, COND_EQUAL**) (sql_select.cc:13300)

==2176==    by 0x641C8B: JOIN::optimize() (sql_select.cc:1067)

branch: maria/5.5

revision-id: sergii@pisem.net-20121127112615-l2mciflv2imoikhy

date: 2012-11-27 12:26:15 +0100

revno: 3587

index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,engine_condition_pushdown=off,index_condition_pushdown=on,derived_merge=on,derived_with_keys=on,firstmatch=on,loosescan=on,materialization=on,in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,outer_join_with_cache=on,semijoin_with_cache=on,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=off,table_elimination=on,extended_keys=off

id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra

1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	

2	SUBQUERY	t2	system	NULL	NULL	NULL	NULL	1	100.00	Using filesort

2	SUBQUERY	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	

Warnings:

Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where 1

SET optimizer_switch = 'in_to_exists=on';

CREATE TABLE t1 (a INT) ENGINE=MyISAM;

INSERT INTO t1 VALUES (1),(9);

CREATE TABLE t2 (b INT) ENGINE=MyISAM;

INSERT INTO t2 VALUES (8);

SELECT * FROM t1 

WHERE ( 1, 1 ) IN ( 

  SELECT a, SUM( DISTINCT a ) 

  FROM t1, t2 

  GROUP BY a 

);