diff --git a/.bzrignore b/.bzrignore
index 759ca4a20bf..35f5199be3c 100644
--- a/.bzrignore
+++ b/.bzrignore
@@ -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
diff --git a/mysql-test/r/distinct.result b/mysql-test/r/distinct.result
index 8525e0f19e4..8cfe5aa78b5 100644
--- a/mysql-test/r/distinct.result
+++ b/mysql-test/r/distinct.result
@@ -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");
diff --git a/mysql-test/r/group_by.result b/mysql-test/r/group_by.result
index d4ffbe43a91..053c2901509 100644
--- a/mysql-test/r/group_by.result
+++ b/mysql-test/r/group_by.result
@@ -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;
diff --git a/mysql-test/r/innodb_mysql.result b/mysql-test/r/innodb_mysql.result
index 63e25b7aa1e..82955af4c8a 100644
--- a/mysql-test/r/innodb_mysql.result
+++ b/mysql-test/r/innodb_mysql.result
@@ -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
diff --git a/mysql-test/t/group_by.test b/mysql-test/t/group_by.test
index 91e69f9db34..b7c28cada46 100644
--- a/mysql-test/t/group_by.test
+++ b/mysql-test/t/group_by.test
@@ -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;
diff --git a/mysql-test/t/innodb_mysql.test b/mysql-test/t/innodb_mysql.test
index adcfec68d3e..949e602a299 100644
--- a/mysql-test/t/innodb_mysql.test
+++ b/mysql-test/t/innodb_mysql.test
@@ -882,4 +882,31 @@ alter table t1 add index(a(1024));
 show create table t1;
 drop table t1;
 
+#
+# 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)
+) 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;
+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;
+
 --echo End of 5.0 tests
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index ac8dc84f118..4be542975b5 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -1030,6 +1030,14 @@ JOIN::optimize()
                                  find_field_in_order_list,
                                  (void *) group_list))
     {
+      /*
+        We have found that grouping can be removed since groups correspond to
+        only one row anyway, but we still have to guarantee correct result
+        order. The line below effectively rewrites the query from GROUP BY
+        <fields> to ORDER BY <fields>. One exception is if skip_sort_order is
+        set (see above), then we can simply skip GROUP BY.
+       */
+      order= skip_sort_order ? 0 : group_list;
       group_list= 0;
       group= 0;
     }