Commit 06a302ef authored by unknown's avatar unknown
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Bug #21302: Result not properly sorted when using an ORDER BY on a second 

             table in a join
 The optimizer removes redundant columns in ORDER BY. It is considering 
redundant every reference to const table column, e.g b in :
create table t1 (a int, b int, primary key(a)); 
select 1 from t1 order by b where a = 1

But it must not remove references to const table columns if the 
const table is an outer table because there still can be 2 values :
the const value and NULL. e.g.:
create table t1 (a int, b int, primary key(a));
select t2.b c from t1 left join t1 t2 on (t1.a = t2.a and t2.a = 5) 
  order by c;


mysql-test/r/join_outer.result:
  Bug #21302: Result not properly sorted when using an ORDER BY on a second 
              table in a join
   - don't remove columns of const tables in ORDER BY if the const table 
     is an outer table.
mysql-test/r/order_by.result:
  Bug #21302: Result not properly sorted when using an ORDER BY on a second 
              table in a join
   - test case
mysql-test/t/order_by.test:
  Bug #21302: Result not properly sorted when using an ORDER BY on a second 
              table in a join
   - test case
sql/sql_select.cc:
  Bug #21302: Result not properly sorted when using an ORDER BY on a second 
              table in a join
   - don't remove columns of const tables in ORDER BY if the const table 
     is an outer table.
parent 1cf65f31

mysql-test/r/join_outer.result

+1 −1
Original line number Diff line number Diff line
@@ -735,7 +735,7 @@ explain select s.*, '*', m.*, (s.match_1_h - m.home) UUX from 
(t2 s left join t1 m on m.match_id = 1) 

order by m.match_id desc;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	s	ALL	NULL	NULL	NULL	NULL	10	

1	SIMPLE	s	ALL	NULL	NULL	NULL	NULL	10	Using temporary; Using filesort

1	SIMPLE	m	const	match_id,match_id_2	match_id	1	const	1	

explain select s.*, '*', m.*, (s.match_1_h - m.home) UUX from 

(t2 s left join t1 m on m.match_id = 1)

mysql-test/r/order_by.result

+37 −0
Original line number Diff line number Diff line
@@ -852,3 +852,40 @@ b a 
20	1

10	2

DROP TABLE t1;

CREATE TABLE t1 (a int, b int, PRIMARY KEY  (a));

INSERT INTO t1 VALUES (1,1), (2,2), (3,3);

explain SELECT t1.b as a, t2.b as c FROM 

t1 LEFT JOIN t1 t2 ON (t1.a = t2.a AND t2.a = 2) 

ORDER BY c;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using temporary; Using filesort

1	SIMPLE	t2	const	PRIMARY	PRIMARY	4	const	1	

SELECT t1.b as a, t2.b as c FROM 

t1 LEFT JOIN t1 t2 ON (t1.a = t2.a AND t2.a = 2) 

ORDER BY c;

a	c

1	NULL

3	NULL

2	2

explain SELECT t1.b as a, t2.b as c FROM 

t1 JOIN t1 t2 ON (t1.a = t2.a AND t2.a = 2)  

ORDER BY c;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t1	const	PRIMARY	PRIMARY	4	const	1	

1	SIMPLE	t2	const	PRIMARY	PRIMARY	4	const	1	

CREATE TABLE t2 LIKE t1;

INSERT INTO t2 SELECT * from t1;

CREATE TABLE t3 LIKE t1;

INSERT INTO t3 SELECT * from t1;

CREATE TABLE t4 LIKE t1;

INSERT INTO t4 SELECT * from t1;

INSERT INTO t1 values (0,0),(4,4);

SELECT t1.*,t2.* FROM t1 LEFT JOIN (t2, t3 LEFT JOIN t4 ON t3.a=t4.a)

ON (t1.a=t2.a AND t1.b=t3.b) order by t2.b;

a	b	a	b

0	0	NULL	NULL

4	4	NULL	NULL

1	1	1	1

2	2	2	2

3	3	3	3

DROP TABLE t1,t2,t3,t4;

mysql-test/t/order_by.test

+32 −0
Original line number Diff line number Diff line
@@ -578,3 +578,35 @@ INSERT INTO t1 VALUES (1,30), (2,20), (1,10), (2,30), (1,20), (2,10); 
DROP TABLE t1;



# End of 4.1 tests



#

# Bug#21302: Result not properly sorted when using an ORDER BY on a second 

#             table in a join

#

CREATE TABLE t1 (a int, b int, PRIMARY KEY  (a));

INSERT INTO t1 VALUES (1,1), (2,2), (3,3);



explain SELECT t1.b as a, t2.b as c FROM 

 t1 LEFT JOIN t1 t2 ON (t1.a = t2.a AND t2.a = 2) 

ORDER BY c;

SELECT t1.b as a, t2.b as c FROM 

 t1 LEFT JOIN t1 t2 ON (t1.a = t2.a AND t2.a = 2) 

ORDER BY c;



# check that it still removes sort of const table

explain SELECT t1.b as a, t2.b as c FROM 

 t1 JOIN t1 t2 ON (t1.a = t2.a AND t2.a = 2)  

ORDER BY c;



CREATE TABLE t2 LIKE t1;

INSERT INTO t2 SELECT * from t1;

CREATE TABLE t3 LIKE t1;

INSERT INTO t3 SELECT * from t1;

CREATE TABLE t4 LIKE t1;

INSERT INTO t4 SELECT * from t1;

INSERT INTO t1 values (0,0),(4,4);



SELECT t1.*,t2.* FROM t1 LEFT JOIN (t2, t3 LEFT JOIN t4 ON t3.a=t4.a)

ON (t1.a=t2.a AND t1.b=t3.b) order by t2.b;



DROP TABLE t1,t2,t3,t4;

sql/sql_select.cc

+2 −1
Original line number Diff line number Diff line
@@ -5976,7 +5976,8 @@ eq_ref_table(JOIN *join, ORDER *start_order, JOIN_TAB *tab) 
  if (tab->cached_eq_ref_table)			// If cached

    return tab->eq_ref_table;

  tab->cached_eq_ref_table=1;

  if (tab->type == JT_CONST)			// We can skip const tables

  /* We can skip const tables only if not an outer table */

  if (tab->type == JT_CONST && !tab->first_inner)

    return (tab->eq_ref_table=1);		/* purecov: inspected */

  if (tab->type != JT_EQ_REF || tab->table->maybe_null)

    return (tab->eq_ref_table=0);		// We must use this