CREATE TABLE t (id INT, a INT, b INT, KEY (a), KEY (b)) ENGINE=INNODB
PARTITION BY HASH (id) PARTITIONS 10;
insert into t values (0,4,1);
insert into t values (6,2,5);
insert into t values (6,7,5);
insert into t values (2,4,6);
insert into t values (3,5,6);
insert into t values (1,3,9);
insert into t values (1,3,9);
insert into t values (3,4,6);
insert into t values (4,4,6);
EXPLAIN SELECT SQL_NO_CACHE COUNT(*) FROM t WHERE a=4 AND b=6;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t	index_merge	a,b	a,b	5,5	NULL	7	Using intersect(a,b); Using where; Using index
EXPLAIN SELECT SQL_NO_CACHE a,b FROM t WHERE a=4 AND b=6;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t	index_merge	a,b	a,b	5,5	NULL	7	Using intersect(a,b); Using where; Using index
SELECT SQL_NO_CACHE * FROM t WHERE a=4 AND b=6 ORDER BY id;
id	a	b
2	4	6
3	4	6
4	4	6
SELECT SQL_NO_CACHE COUNT(*) FROM t WHERE a=4 AND b=6;
COUNT(*)
3
DROP TABLE t;
