drop table if exists t1,t2;
#
# Bug#50939: Loose Index Scan unduly relies on engine to remember range 
# endpoints
#
CREATE TABLE t1 (
a INT,
b INT,
KEY ( a, b )
) PARTITION BY HASH (a) PARTITIONS 1;
CREATE TABLE t2 (
a INT,
b INT,
KEY ( a, b )
);
INSERT INTO t1 VALUES (1, 1), (2, 2), (3, 3), (4, 4), (5, 5);
INSERT INTO t1 SELECT a +  5, b +  5 FROM t1;
INSERT INTO t1 SELECT a + 10, b + 10 FROM t1;
INSERT INTO t1 SELECT a + 20, b + 20 FROM t1;
INSERT INTO t1 SELECT a + 40, b + 40 FROM t1;
INSERT INTO t2 SELECT * FROM t1;
# plans should be identical
EXPLAIN SELECT a, MAX(b) FROM t1 WHERE a IN (10,100) GROUP BY a;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	range	a	a	5	NULL	1	Using where; Using index for group-by
EXPLAIN SELECT a, MAX(b) FROM t2 WHERE a IN (10,100) GROUP BY a;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t2	range	a	a	5	NULL	2	Using where; Using index for group-by
FLUSH status;
SELECT a, MAX(b) FROM t1 WHERE a IN (10, 100) GROUP BY a;
a	MAX(b)
10	10
# Should be no more than 4 reads.
SHOW status LIKE 'handler_read_key';
Variable_name	Value
Handler_read_key	4
FLUSH status;
SELECT a, MAX(b) FROM t2 WHERE a IN (10, 100) GROUP BY a;
a	MAX(b)
10	10
# Should be no more than 4 reads.
SHOW status LIKE 'handler_read_key';
Variable_name	Value
Handler_read_key	4
DROP TABLE t1, t2;
