Commit a4d5d920 authored by mhansson/martin@linux-st28.site's avatar mhansson/martin@linux-st28.site
Browse files

Bug #30596 GROUP BY optimization gives wrong result order 

The optimization that uses a unique index to remove GROUP BY, did not 
ensure that the index was actually used, thus violating the ORDER BY
that is impled by GROUP BY.
Fixed by replacing GROUP BY with ORDER BY if the GROUP BY clause contains
a unique index. In case GROUP BY ... ORDER BY null is used, GROUP BY is
simply removed.
parent c40fe57f

.bzrignore

+5 −0
Original line number Diff line number Diff line
@@ -1345,3 +1345,8 @@ zlib/*.vcproj 
debian/control

debian/defs.mk

include/abi_check

support-files/mysqld_multi.server

tests/bug25714

cscope.in.out

cscope.out

cscope.po.out

mysql-test/r/distinct.result

+3 −3
Original line number Diff line number Diff line
@@ -526,10 +526,10 @@ id select_type table type possible_keys key key_len ref rows Extra 
1	SIMPLE	t1	index	NULL	PRIMARY	4	NULL	3	Using index

EXPLAIN SELECT a,b FROM t1 GROUP BY a,b;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	

1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using filesort

EXPLAIN SELECT DISTINCT a,b FROM t1 GROUP BY a,b;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	

1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using filesort

CREATE TABLE t2(a INT, b INT NOT NULL, c INT NOT NULL, d INT, 

PRIMARY KEY (a,b));

INSERT INTO t2 VALUES (1,1,1,50), (1,2,3,40), (2,1,3,4);
@@ -554,7 +554,7 @@ id select_type table type possible_keys key key_len ref rows Extra 
CREATE UNIQUE INDEX c_b_unq ON t2 (c,b);

EXPLAIN SELECT DISTINCT a,b,d FROM t2 GROUP BY c,b,d;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	3	

1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	3	Using filesort

DROP TABLE t1,t2;

create table t1 (id int, dsc varchar(50));

insert into t1 values (1, "line number one"), (2, "line number two"), (3, "line number three");

mysql-test/r/group_by.result

+49 −0
Original line number Diff line number Diff line
@@ -1064,3 +1064,52 @@ select t1.f1,t.* from t1, t1 t group by 1; 
ERROR 42000: 'test.t.f1' isn't in GROUP BY

drop table t1;

SET SQL_MODE = '';

CREATE TABLE t1(

a INT, 

b INT NOT NULL, 

c INT NOT NULL, 

d INT, 

UNIQUE KEY (c,b)

);

INSERT INTO t1 VALUES (1,1,1,50), (1,2,3,40), (2,1,3,4);

EXPLAIN SELECT c,b,d FROM t1 GROUP BY c,b,d;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using filesort

SELECT c,b,d FROM t1 GROUP BY c,b,d;

c	b	d

1	1	50

3	1	4

3	2	40

EXPLAIN SELECT c,b,d FROM t1 GROUP BY c,b,d ORDER BY NULL;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	

SELECT c,b,d FROM t1 GROUP BY c,b,d ORDER BY NULL;

c	b	d

1	1	50

3	2	40

3	1	4

EXPLAIN SELECT c,b,d FROM t1 ORDER BY c,b,d;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using filesort

SELECT c,b,d FROM t1 ORDER BY c,b,d;

c	b	d

1	1	50

3	1	4

3	2	40

EXPLAIN SELECT c,b,d FROM t1 GROUP BY c,b;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using filesort

SELECT c,b,d FROM t1 GROUP BY c,b;

c	b	d

1	1	50

3	1	4

3	2	40

EXPLAIN SELECT c,b   FROM t1 GROUP BY c,b;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	index	NULL	c	8	NULL	3	Using index

SELECT c,b   FROM t1 GROUP BY c,b;

c	b

1	1

3	1

3	2

DROP TABLE t1;

mysql-test/r/innodb_mysql.result

+49 −0
Original line number Diff line number Diff line
@@ -1047,4 +1047,53 @@ t1 CREATE TABLE `t1` ( 
  KEY `a` (`a`(255))

) ENGINE=InnoDB DEFAULT CHARSET=utf8

drop table t1;

CREATE TABLE t1(

a INT, 

b INT NOT NULL, 

c INT NOT NULL, 

d INT, 

UNIQUE KEY (c,b)

) engine=innodb;

INSERT INTO t1 VALUES (1,1,1,50), (1,2,3,40), (2,1,3,4);

EXPLAIN SELECT c,b,d FROM t1 GROUP BY c,b,d;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using filesort

SELECT c,b,d FROM t1 GROUP BY c,b,d;

c	b	d

1	1	50

3	1	4

3	2	40

EXPLAIN SELECT c,b,d FROM t1 GROUP BY c,b,d ORDER BY NULL;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	

SELECT c,b,d FROM t1 GROUP BY c,b,d ORDER BY NULL;

c	b	d

1	1	50

3	1	4

3	2	40

EXPLAIN SELECT c,b,d FROM t1 ORDER BY c,b,d;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using filesort

SELECT c,b,d FROM t1 ORDER BY c,b,d;

c	b	d

1	1	50

3	1	4

3	2	40

EXPLAIN SELECT c,b,d FROM t1 GROUP BY c,b;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	index	NULL	c	8	NULL	3	

SELECT c,b,d FROM t1 GROUP BY c,b;

c	b	d

1	1	50

3	1	4

3	2	40

EXPLAIN SELECT c,b   FROM t1 GROUP BY c,b;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	index	NULL	c	8	NULL	3	Using index

SELECT c,b   FROM t1 GROUP BY c,b;

c	b

1	1

3	1

3	2

DROP TABLE t1;

End of 5.0 tests

mysql-test/t/group_by.test

+27 −0
Original line number Diff line number Diff line
@@ -788,3 +788,30 @@ select * from t1 group by f1, f2; 
select t1.f1,t.* from t1, t1 t group by 1;

drop table t1;

SET SQL_MODE = '';



#

# Bug#30596: GROUP BY optimization gives wrong result order

#

CREATE TABLE t1(

  a INT, 

  b INT NOT NULL, 

  c INT NOT NULL, 

  d INT, 

  UNIQUE KEY (c,b)

);



INSERT INTO t1 VALUES (1,1,1,50), (1,2,3,40), (2,1,3,4);



EXPLAIN SELECT c,b,d FROM t1 GROUP BY c,b,d;

SELECT c,b,d FROM t1 GROUP BY c,b,d;

EXPLAIN SELECT c,b,d FROM t1 GROUP BY c,b,d ORDER BY NULL;

SELECT c,b,d FROM t1 GROUP BY c,b,d ORDER BY NULL;

EXPLAIN SELECT c,b,d FROM t1 ORDER BY c,b,d;

SELECT c,b,d FROM t1 ORDER BY c,b,d;



EXPLAIN SELECT c,b,d FROM t1 GROUP BY c,b;

SELECT c,b,d FROM t1 GROUP BY c,b;

EXPLAIN SELECT c,b   FROM t1 GROUP BY c,b;

SELECT c,b   FROM t1 GROUP BY c,b;



DROP TABLE t1;