config root man

#
# WL#6986 : Make switching of index due to order by limit cost based
#
# Testcase for Bug#16522053
CREATE TABLE t1 (
pk INT PRIMARY KEY AUTO_INCREMENT,
i INT,
j INT,
INDEX (i),
INDEX (j)
);
INSERT INTO t1 (i,j) VALUES (1,1);
set @d=1;
INSERT INTO t1 (i,j) SELECT i+@d, j+@d from t1;
set @d=@d*2;
INSERT INTO t1 (i,j) SELECT i+@d, j+@d from t1;
set @d=@d*2;
INSERT INTO t1 (i,j) SELECT i+@d, j+@d from t1;
set @d=@d*2;
INSERT INTO t1 (i,j) SELECT i+@d, j+@d from t1;
set @d=@d*2;
INSERT INTO t1 (i,j) SELECT i+@d, j+@d from t1;
set @d=@d*2;
INSERT INTO t1 (i,j) SELECT i+@d, j+@d from t1;
set @d=@d*2;
INSERT INTO t1 (i,j) SELECT i+@d, j+@d from t1;
set @d=@d*2;
ANALYZE TABLE t1;
Table	Op	Msg_type	Msg_text
test.t1	analyze	status	OK
EXPLAIN SELECT * FROM t1
WHERE i<100 AND j<10
ORDER BY i LIMIT 5;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t1	NULL	range	i,j	j	5	NULL	9	77.34	Using index condition; Using where; Using filesort
Warnings:
Note	1003	/* select#1 */ select `test`.`t1`.`pk` AS `pk`,`test`.`t1`.`i` AS `i`,`test`.`t1`.`j` AS `j` from `test`.`t1` where ((`test`.`t1`.`i` < 100) and (`test`.`t1`.`j` < 10)) order by `test`.`t1`.`i` limit 5
SELECT * FROM t1
WHERE i<100 AND j<10
ORDER BY i LIMIT 5;
pk	i	j
1	1	1
2	2	2
3	3	3
4	4	4
6	5	5
DROP TABLE t1;
CREATE TABLE t0 (
i0 INTEGER NOT NULL
);
INSERT INTO t0 VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
CREATE TABLE t1 (
pk INTEGER PRIMARY KEY,
i1 INTEGER NOT NULL,
i2 INTEGER NOT NULL,
INDEX k1 (i1),
INDEX k2 (i1,i2)
) ENGINE=InnoDB;
INSERT INTO t1
SELECT a0.i0 + 10*a1.i0 + 100*a0.i0 + 1000*a1.i0,
(a0.i0 + 10*a1.i0 + 100*a0.i0 + 1000*a1.i0) % 1000,
(a0.i0 + 10*a1.i0 + 100*a0.i0 + 1000*a1.i0) % 1000
FROM t0 AS a0, t0 AS a1;
CREATE TABLE t2 (
pk INTEGER PRIMARY KEY,
i1 INTEGER NOT NULL,
INDEX k1 (i1)
) ENGINE=InnoDB;
INSERT INTO t2
SELECT a0.i0 + 10*a1.i0 + 100*a0.i0 + 1000*a1.i0,
(a0.i0 + 10*a1.i0 + 100*a0.i0 + 1000*a1.i0) % 500
FROM t0 AS a0, t0 AS a1;
ANALYZE TABLE t1,t2;
Table	Op	Msg_type	Msg_text
test.t1	analyze	status	OK
test.t2	analyze	status	OK
# Query should use index to optimize the ORDER BY LIMIT
EXPLAIN SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 and t1.i1 > 2
ORDER BY t1.i1 LIMIT 2;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t1	NULL	index	PRIMARY,k1,k2	k1	4	NULL	6	29.70	Using where
1	SIMPLE	t2	NULL	ref	k1	k1	4	test.t1.i1	1	100.00	Using index
Warnings:
Note	1003	/* select#1 */ select `test`.`t1`.`pk` AS `pk`,`test`.`t1`.`i1` AS `i1`,`test`.`t1`.`i2` AS `i2`,`test`.`t2`.`pk` AS `pk`,`test`.`t2`.`i1` AS `i1` from `test`.`t1` straight_join `test`.`t2` where ((`test`.`t2`.`i1` = `test`.`t1`.`i1`) and (`test`.`t1`.`pk` > 7000) and (`test`.`t1`.`i1` > 2)) order by `test`.`t1`.`i1` limit 2
# Query should not make the switch to use index to
# optimize ORDER BY LIMIT. So should be using filesort
EXPLAIN SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 and t1.i1 > 2
ORDER BY t1.i1 LIMIT 5;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t1	NULL	range	PRIMARY,k1,k2	PRIMARY	4	NULL	30	99.00	Using where; Using filesort
1	SIMPLE	t2	NULL	ref	k1	k1	4	test.t1.i1	1	100.00	Using index
Warnings:
Note	1003	/* select#1 */ select `test`.`t1`.`pk` AS `pk`,`test`.`t1`.`i1` AS `i1`,`test`.`t1`.`i2` AS `i2`,`test`.`t2`.`pk` AS `pk`,`test`.`t2`.`i1` AS `i1` from `test`.`t1` straight_join `test`.`t2` where ((`test`.`t2`.`i1` = `test`.`t1`.`i1`) and (`test`.`t1`.`pk` > 7000) and (`test`.`t1`.`i1` > 2)) order by `test`.`t1`.`i1` limit 5
SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 and t1.i1 > 2
ORDER BY t1.i1 LIMIT 5;
pk	i1	i2	pk	i1
7070	70	70	7070	70
8080	80	80	8080	80
9090	90	90	9090	90
7171	171	171	7171	171
8181	181	181	8181	181
# Changing range condition on i1 should make
# key on i1 get picked to give the order
EXPLAIN SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 and t1.i1 > 800
ORDER BY t1.i1 LIMIT 5;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t1	NULL	range	PRIMARY,k1,k2	k2	4	NULL	20	30.00	Using where; Using index
1	SIMPLE	t2	NULL	ref	k1	k1	4	test.t1.i1	1	100.00	Using index
Warnings:
Note	1003	/* select#1 */ select `test`.`t1`.`pk` AS `pk`,`test`.`t1`.`i1` AS `i1`,`test`.`t1`.`i2` AS `i2`,`test`.`t2`.`pk` AS `pk`,`test`.`t2`.`i1` AS `i1` from `test`.`t1` straight_join `test`.`t2` where ((`test`.`t2`.`i1` = `test`.`t1`.`i1`) and (`test`.`t1`.`pk` > 7000) and (`test`.`t1`.`i1` > 800)) order by `test`.`t1`.`i1` limit 5
SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 and t1.i1 > 800
ORDER BY t1.i1 LIMIT 5;
pk	i1	i2	pk	i1
# Use range condition only on pk to see if switch
# happens just for ORDER BY LIMIT
# Should not happen unless range results in too
# many records
EXPLAIN SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 ORDER BY t1.i1 LIMIT 5;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t1	NULL	range	PRIMARY,k1,k2	PRIMARY	4	NULL	30	100.00	Using where; Using filesort
1	SIMPLE	t2	NULL	ref	k1	k1	4	test.t1.i1	1	100.00	Using index
Warnings:
Note	1003	/* select#1 */ select `test`.`t1`.`pk` AS `pk`,`test`.`t1`.`i1` AS `i1`,`test`.`t1`.`i2` AS `i2`,`test`.`t2`.`pk` AS `pk`,`test`.`t2`.`i1` AS `i1` from `test`.`t1` straight_join `test`.`t2` where ((`test`.`t2`.`i1` = `test`.`t1`.`i1`) and (`test`.`t1`.`pk` > 7000)) order by `test`.`t1`.`i1` limit 5
SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 ORDER BY t1.i1 LIMIT 5;
pk	i1	i2	pk	i1
7070	70	70	7070	70
8080	80	80	8080	80
9090	90	90	9090	90
7171	171	171	7171	171
8181	181	181	8181	181
EXPLAIN SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 1000 ORDER BY t1.i1 LIMIT 5;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t1	NULL	index	PRIMARY,k1,k2	k1	4	NULL	5	90.00	Using where
1	SIMPLE	t2	NULL	ref	k1	k1	4	test.t1.i1	1	100.00	Using index
Warnings:
Note	1003	/* select#1 */ select `test`.`t1`.`pk` AS `pk`,`test`.`t1`.`i1` AS `i1`,`test`.`t1`.`i2` AS `i2`,`test`.`t2`.`pk` AS `pk`,`test`.`t2`.`i1` AS `i1` from `test`.`t1` straight_join `test`.`t2` where ((`test`.`t2`.`i1` = `test`.`t1`.`i1`) and (`test`.`t1`.`pk` > 1000)) order by `test`.`t1`.`i1` limit 5
SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 1000 ORDER BY t1.i1 LIMIT 5;
pk	i1	i2	pk	i1
1010	10	10	1010	10
2020	20	20	2020	20
3030	30	30	3030	30
4040	40	40	4040	40
5050	50	50	5050	50
# check if switch happens when the index for order 
# by is non-covering
EXPLAIN SELECT t1.i1,t1.i2 FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1 
WHERE t1.pk > 100 ORDER BY t1.i1 LIMIT 5;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t1	NULL	index	PRIMARY,k1,k2	k1	4	NULL	5	99.00	Using where
1	SIMPLE	t2	NULL	ref	k1	k1	4	test.t1.i1	1	100.00	Using index
Warnings:
Note	1003	/* select#1 */ select `test`.`t1`.`i1` AS `i1`,`test`.`t1`.`i2` AS `i2` from `test`.`t1` straight_join `test`.`t2` where ((`test`.`t2`.`i1` = `test`.`t1`.`i1`) and (`test`.`t1`.`pk` > 100)) order by `test`.`t1`.`i1` limit 5
SELECT t1.i1,t1.i2 FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1 
WHERE t1.pk > 100 ORDER BY t1.i1 LIMIT 5;
i1	i2
10	10
20	20
30	30
40	40
50	50
# Reduce the fanout for table t2 and check
# that index for order by is not choosen
EXPLAIN SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 and t2.pk = 100 ORDER BY t1.i1 LIMIT 5;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t1	NULL	range	PRIMARY,k1,k2	PRIMARY	4	NULL	30	100.00	Using where; Using filesort
1	SIMPLE	t2	NULL	const	PRIMARY,k1	PRIMARY	4	const	1	5.00	Using where
Warnings:
Note	1003	/* select#1 */ select `test`.`t1`.`pk` AS `pk`,`test`.`t1`.`i1` AS `i1`,`test`.`t1`.`i2` AS `i2`,`test`.`t2`.`pk` AS `pk`,`test`.`t2`.`i1` AS `i1` from `test`.`t1` straight_join `test`.`t2` where ((`test`.`t2`.`i1` = `test`.`t1`.`i1`) and (`test`.`t2`.`pk` = 100) and (`test`.`t1`.`pk` > 7000)) order by `test`.`t1`.`i1` limit 5
SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 and t2.pk = 100 ORDER BY t1.i1 LIMIT 5;
pk	i1	i2	pk	i1
# Increase the fanout to see if index gets choosen
# for order by for which range scan was choosen
# earlier
INSERT INTO t2
SELECT a0.i0 + 10*a1.i0 + 100*a0.i0 + 1000*a1.i0 + 1,
(a0.i0 + 10*a1.i0 + 100*a0.i0 + 1000*a1.i0) % 500
FROM t0 AS a0, t0 AS a1;
ANALYZE TABLE t2;
Table	Op	Msg_type	Msg_text
test.t2	analyze	status	OK
EXPLAIN SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 ORDER BY t1.i1 LIMIT 5;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t1	NULL	index	PRIMARY,k1,k2	k1	4	NULL	6	30.00	Using where
1	SIMPLE	t2	NULL	ref	k1	k1	4	test.t1.i1	2	100.00	Using index
Warnings:
Note	1003	/* select#1 */ select `test`.`t1`.`pk` AS `pk`,`test`.`t1`.`i1` AS `i1`,`test`.`t1`.`i2` AS `i2`,`test`.`t2`.`pk` AS `pk`,`test`.`t2`.`i1` AS `i1` from `test`.`t1` straight_join `test`.`t2` where ((`test`.`t2`.`i1` = `test`.`t1`.`i1`) and (`test`.`t1`.`pk` > 7000)) order by `test`.`t1`.`i1` limit 5
SELECT * FROM t1 STRAIGHT_JOIN t2 ON t1.i1=t2.i1
WHERE t1.pk > 7000 ORDER BY t1.i1 LIMIT 5;
pk	i1	i2	pk	i1
7070	70	70	7070	70
7070	70	70	7071	70
8080	80	80	8080	80
8080	80	80	8081	80
9090	90	90	9090	90
# Check if the index for order by is used when
# force index is done on order by
EXPLAIN SELECT * FROM t1 FORCE INDEX FOR ORDER BY (k2) STRAIGHT_JOIN t2 ON
t1.i1=t2.i1 WHERE t1.pk > 7000 ORDER BY t1.i1 LIMIT 5;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t1	NULL	index	PRIMARY,k1,k2	k2	8	NULL	6	30.00	Using where; Using index
1	SIMPLE	t2	NULL	ref	k1	k1	4	test.t1.i1	2	100.00	Using index
Warnings:
Note	1003	/* select#1 */ select `test`.`t1`.`pk` AS `pk`,`test`.`t1`.`i1` AS `i1`,`test`.`t1`.`i2` AS `i2`,`test`.`t2`.`pk` AS `pk`,`test`.`t2`.`i1` AS `i1` from `test`.`t1` FORCE INDEX FOR ORDER BY (`k2`) straight_join `test`.`t2` where ((`test`.`t2`.`i1` = `test`.`t1`.`i1`) and (`test`.`t1`.`pk` > 7000)) order by `test`.`t1`.`i1` limit 5
SELECT * FROM t1 FORCE INDEX FOR ORDER BY (k2) STRAIGHT_JOIN t2 ON
t1.i1=t2.i1 WHERE t1.pk > 7000 ORDER BY t1.i1 LIMIT 5;
pk	i1	i2	pk	i1
7070	70	70	7070	70
7070	70	70	7071	70
8080	80	80	8080	80
8080	80	80	8081	80
9090	90	90	9090	90
DROP TABLE t0, t1, t2;
#
# Bug 31686878 - BACKPORT MAIN BUG 30348211 TO RELEASE 5.7
#
CREATE TABLE t (id BIGINT NOT NULL, other_id BIGINT NOT NULL,
covered_column VARCHAR(50) NOT NULL, non_covered_column VARCHAR(50) NOT NULL,
PRIMARY KEY (id),
INDEX index_other_id_covered_column (other_id, covered_column));
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (10, 10, '10', '10');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (9, 9, '9', '9');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (8, 8, '8', '8');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (7, 7, '7', '7');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (6, 6, '6', '6');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (5, 5, '5', '5');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (4, 4, '4', '4');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (3, 3, '3', '3');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (2, 2, '2', '2');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (1, 1, '1', '1');
SET
optimizer_trace = "enabled=on",
optimizer_trace_max_mem_size = 1000000,
end_markers_in_json = ON;
SET optimizer_switch = "prefer_ordering_index=on";
ANALYZE TABLE t;
Table	Op	Msg_type	Msg_text
test.t	analyze	status	OK
EXPLAIN SELECT non_covered_column FROM t WHERE other_id > 3 ORDER BY id ASC LIMIT 2;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t	NULL	index	index_other_id_covered_column	PRIMARY	8	NULL	2	70.00	Using where
Warnings:
Note	1003	/* select#1 */ select `test`.`t`.`non_covered_column` AS `non_covered_column` from `test`.`t` where (`test`.`t`.`other_id` > 3) order by `test`.`t`.`id` limit 2
SELECT (trace LIKE '%"plan_changed": true%') AS should_be_1 FROM information_schema.optimizer_trace;
should_be_1
1
SET optimizer_switch = "prefer_ordering_index=off";
EXPLAIN SELECT non_covered_column FROM t WHERE other_id > 3 ORDER BY id ASC LIMIT 2;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t	NULL	range	index_other_id_covered_column	index_other_id_covered_column	8	NULL	7	100.00	Using index condition; Using filesort
Warnings:
Note	1003	/* select#1 */ select `test`.`t`.`non_covered_column` AS `non_covered_column` from `test`.`t` where (`test`.`t`.`other_id` > 3) order by `test`.`t`.`id` limit 2
SELECT (trace LIKE '%"plan_changed": true%') AS should_be_0 FROM information_schema.optimizer_trace;
should_be_0
0
SET optimizer_switch = default;
EXPLAIN SELECT non_covered_column FROM t WHERE other_id > 3 ORDER BY id ASC LIMIT 2;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t	NULL	index	index_other_id_covered_column	PRIMARY	8	NULL	2	70.00	Using where
Warnings:
Note	1003	/* select#1 */ select `test`.`t`.`non_covered_column` AS `non_covered_column` from `test`.`t` where (`test`.`t`.`other_id` > 3) order by `test`.`t`.`id` limit 2
SELECT (trace LIKE '%"plan_changed": true%') AS should_be_1 FROM information_schema.optimizer_trace;
should_be_1
1
SET optimizer_switch = "prefer_ordering_index=on";
EXPLAIN SELECT non_covered_column FROM t FORCE INDEX(PRIMARY) WHERE other_id > 3 ORDER BY id ASC LIMIT 2;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t	NULL	index	NULL	PRIMARY	8	NULL	2	33.33	Using where
Warnings:
Note	1003	/* select#1 */ select `test`.`t`.`non_covered_column` AS `non_covered_column` from `test`.`t` FORCE INDEX (PRIMARY) where (`test`.`t`.`other_id` > 3) order by `test`.`t`.`id` limit 2
SELECT (trace LIKE '%"plan_changed": true%') AS should_be_1 FROM information_schema.optimizer_trace;
should_be_1
1
SET optimizer_switch = "prefer_ordering_index=off";
EXPLAIN SELECT non_covered_column FROM t FORCE INDEX(PRIMARY) WHERE other_id > 3 ORDER BY id ASC LIMIT 2;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t	NULL	index	NULL	PRIMARY	8	NULL	2	33.33	Using where
Warnings:
Note	1003	/* select#1 */ select `test`.`t`.`non_covered_column` AS `non_covered_column` from `test`.`t` FORCE INDEX (PRIMARY) where (`test`.`t`.`other_id` > 3) order by `test`.`t`.`id` limit 2
SELECT (trace LIKE '%"plan_changed": true%') AS should_be_1 FROM information_schema.optimizer_trace;
should_be_1
1
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (10+1+10, 10, '10', '10');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (9+1+10, 9, '9', '9');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (8+1+10, 8, '8', '8');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (7+1+10, 7, '7', '7');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (6+1+10, 6, '6', '6');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (5+1+10, 5, '5', '5');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (4+1+10, 4, '4', '4');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (3+1+10, 3, '3', '3');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (2+1+10, 2, '2', '2');
INSERT INTO t (id, other_id, covered_column, non_covered_column)
VALUES (1+1+10, 1, '1', '1');
SET optimizer_switch = "prefer_ordering_index=on";
ANALYZE TABLE t;
Table	Op	Msg_type	Msg_text
test.t	analyze	status	OK
EXPLAIN SELECT non_covered_column FROM t WHERE id > 8 GROUP BY other_id LIMIT 1;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t	NULL	index	PRIMARY,index_other_id_covered_column	index_other_id_covered_column	60	NULL	3	60.00	Using where
Warnings:
Note	1003	/* select#1 */ select `test`.`t`.`non_covered_column` AS `non_covered_column` from `test`.`t` where (`test`.`t`.`id` > 8) group by `test`.`t`.`other_id` limit 1
SELECT (trace LIKE '%"plan_changed": true%') AS should_be_1 FROM information_schema.optimizer_trace;
should_be_1
1
SET optimizer_switch = "prefer_ordering_index=off";
SELECT (trace LIKE '%"plan_changed": true%') AS should_be_0 FROM information_schema.optimizer_trace;
should_be_0
0
SET optimizer_switch = default;
EXPLAIN SELECT non_covered_column FROM t WHERE id > 8 GROUP BY other_id LIMIT 1;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t	NULL	index	PRIMARY,index_other_id_covered_column	index_other_id_covered_column	60	NULL	3	60.00	Using where
Warnings:
Note	1003	/* select#1 */ select `test`.`t`.`non_covered_column` AS `non_covered_column` from `test`.`t` where (`test`.`t`.`id` > 8) group by `test`.`t`.`other_id` limit 1
SELECT (trace LIKE '%"plan_changed": true%') AS should_be_1 FROM information_schema.optimizer_trace;
should_be_1
1
SET optimizer_switch = "prefer_ordering_index=on";
EXPLAIN SELECT non_covered_column FROM t FORCE INDEX FOR GROUP BY (index_other_id_covered_column) WHERE id > 8 GROUP BY other_id LIMIT 1;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t	NULL	index	PRIMARY,index_other_id_covered_column	index_other_id_covered_column	60	NULL	3	60.00	Using where
Warnings:
Note	1003	/* select#1 */ select `test`.`t`.`non_covered_column` AS `non_covered_column` from `test`.`t` FORCE INDEX FOR GROUP BY (`index_other_id_covered_column`) where (`test`.`t`.`id` > 8) group by `test`.`t`.`other_id` limit 1
SELECT (trace LIKE '%"plan_changed": true%') AS should_be_1 FROM information_schema.optimizer_trace;
should_be_1
1
SET optimizer_switch = "prefer_ordering_index=off";
EXPLAIN SELECT non_covered_column FROM t FORCE INDEX FOR GROUP BY (index_other_id_covered_column) WHERE id > 8 GROUP BY other_id LIMIT 1;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	t	NULL	index	PRIMARY,index_other_id_covered_column	index_other_id_covered_column	60	NULL	3	60.00	Using where
Warnings:
Note	1003	/* select#1 */ select `test`.`t`.`non_covered_column` AS `non_covered_column` from `test`.`t` FORCE INDEX FOR GROUP BY (`index_other_id_covered_column`) where (`test`.`t`.`id` > 8) group by `test`.`t`.`other_id` limit 1
SELECT (trace LIKE '%"plan_changed": true%') AS should_be_1 FROM information_schema.optimizer_trace;
should_be_1
1
DROP TABLE t;