LevelDB: IN subquery by secondary key with NULL among values returns true instead of NULL

CREATE TABLE t1 (pk INT PRIMARY KEY, a INT, KEY(a)) ENGINE=LevelDB;

INSERT INTO t1 VALUES (1, NULL),(2, 8);

SELECT ( 3 ) NOT IN ( SELECT a FROM t1 );

( 3 ) NOT IN ( SELECT a FROM t1 )

1

EXPLAIN EXTENDED

SELECT ( 3 ) IN ( SELECT a FROM t1 );

id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra

1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used

2	DEPENDENT SUBQUERY	t1	index_subquery	a	a	5	const	20	100.00	Using index

Warnings:

Note	1003	/* select#1 */ select <in_optimizer>(3,<exists>(<index_lookup>(<cache>(3) in t1 on a checking NULL having <is_not_null_test>(`test`.`t1`.`a`)))) AS `( 3 ) IN ( SELECT a FROM t1 )`

CREATE TABLE t1 (pk INT PRIMARY KEY, a INT, KEY(a)) ENGINE=LevelDB;

INSERT INTO t1 VALUES (1, NULL),(2, 8);

SELECT ( 3 ) NOT IN ( SELECT a FROM t1 );

revision-id: psergey@askmonty.org-20130125181032-kuuhprzmkes6p9u0

revno: 4517

branch-nick: mysql-5.6-leveldb