Wrong result (missing rows) on select with secondary keys and index_merge

CREATE TABLE t1 (

pk INT PRIMARY KEY,

a INT, b INT, c VARCHAR(2),

KEY(a), KEY(b), KEY(c)

) ENGINE=LevelDB;

INSERT INTO t1 VALUES   

(1, 11, 101, 'p'), ( 2, 12, 102, 'h'), (3, 13, 103, 'z'), (4, 14, 104, 'h');

SELECT a, b, c FROM t1 WHERE 

c IN ( 'p', 'u' ) 

OR c IN ( 'h', 'l', 'gw' ) 

OR (  b > 255 OR a IN ( 223, 255 ) ) 

  AND ( b = 500 OR c IS NULL )

;

a	b	c

11	101	p

a	b	c

11	101	p

12	102	h

14	104	h

EXPLAIN EXTENDED

SELECT a, b, c FROM t1 WHERE 

c IN ( 'p', 'u' ) 

OR c IN ( 'h', 'l', 'gw' ) 

OR (  b > 255 OR a IN ( 223, 255 ) ) 

AND ( b = 500 OR c IS NULL )

;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra

1	SIMPLE	t1	index_merge	a,b,c	b,a,c	5,5,5	NULL	50	100.00	Using sort_union(b,a,c); Using where

Warnings:

Note	1003	/* select#1 */ select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t1`.`c` AS `c` from `test`.`t1` where ((`test`.`t1`.`c` in ('p','u')) or (`test`.`t1`.`c` in ('h','l','gw')) or (((`test`.`t1`.`b` > 255) or (`test`.`t1`.`a` in (223,255))) and ((`test`.`t1`.`b` = 500) or isnull(`test`.`t1`.`c`))))

@@optimizer_switch

index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,subquery_materialization_cost_based=on

CREATE TABLE t1 (

  pk INT PRIMARY KEY,

  a INT, b INT, c VARCHAR(2),

  KEY(a), KEY(b), KEY(c)

) ENGINE=LevelDB;

INSERT INTO t1 VALUES   

  (1, 11, 101, 'p'), ( 2, 12, 102, 'h'), 

  (3, 13, 103, 'z'), (4, 14, 104, 'h');

SELECT a, b, c FROM t1 WHERE 

  c IN ( 'p', 'u' ) 

  OR c IN ( 'h', 'l', 'gw' ) 

  OR (  b > 255 OR a IN ( 223, 255 ) ) 

    AND ( b = 500 OR c IS NULL )

;

revision-id: psergey@askmonty.org-20130123185233-7xokxc9ck9nosb2l

revno: 4509

branch-nick: mysql-5.6-leveldb