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Bug #31001: ORDER BY DESC in InnoDB not working

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The optimizer sets index traversal in reverse order only if there are 
used key parts that are not compared to a constant.
However using the primary key as an ORDER BY suffix rendered the check
incomplete : going in reverse order must still be used even if 
all the parts of the secondary key are compared to a constant.

Fixed by relaxing the check and set reverse traversal even when all
the secondary index keyparts are compared to a const.
Also account for the case when all the primary keys are compared to a
constant.


mysql-test/include/mix1.inc:
  Bug #31001: test case
mysql-test/r/innodb_mysql.result:
  Bug #31001: test case
sql/sql_select.cc:
  Bug #31001: 
   - account for the case when all the primary key parts are compared
     to a constant.
   - force test_if_skip_sort_order to go backwards over the key even 
     when the number of keyparts used is the same as the number of
     keyparts equal to a constant. (because of the primary key
     suffix).
This commit is contained in:
unknown 2007-09-14 18:20:17 +03:00
parent c0a9e9961e
commit d4042af885
3 changed files with 127 additions and 1 deletions
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23
mysql-test/include/mix1.inc
View file

@ -939,6 +939,29 @@ alter table t1 add index(a(1024));
show create table t1;
drop table t1;
#
# Bug #31001: ORDER BY DESC in InnoDB not working
#
CREATE TABLE t1 (a INT, b INT, PRIMARY KEY (a), INDEX b (b)) ENGINE=InnoDB;
INSERT INTO t1(a,b) VALUES (1,1), (2,2), (3,2);
#The two queries below should produce different results, but they don't.
query_vertical EXPLAIN SELECT * FROM t1 WHERE b=2 ORDER BY a ASC;
SELECT * FROM t1 WHERE b=2 ORDER BY a ASC;
query_vertical EXPLAIN SELECT * FROM t1 WHERE b=2 ORDER BY a DESC;
SELECT * FROM t1 WHERE b=2 ORDER BY a DESC;
query_vertical EXPLAIN SELECT * FROM t1 ORDER BY b ASC, a ASC;
SELECT * FROM t1 ORDER BY b ASC, a ASC;
query_vertical EXPLAIN SELECT * FROM t1 ORDER BY b DESC, a DESC;
SELECT * FROM t1 ORDER BY b DESC, a DESC;
query_vertical EXPLAIN SELECT * FROM t1 ORDER BY b ASC, a DESC;
SELECT * FROM t1 ORDER BY b ASC, a DESC;
query_vertical EXPLAIN SELECT * FROM t1 ORDER BY b DESC, a ASC;
SELECT * FROM t1 ORDER BY b DESC, a ASC;
DROP TABLE t1;
--echo End of 5.0 tests
# Fix for BUG#19243 "wrong LAST_INSERT_ID() after ON DUPLICATE KEY

97
mysql-test/r/innodb_mysql.result
View file

@ -1123,6 +1123,103 @@ t1 CREATE TABLE `t1` (
KEY `a` (`a`(255))
) ENGINE=InnoDB DEFAULT CHARSET=utf8
drop table t1;
CREATE TABLE t1 (a INT, b INT, PRIMARY KEY (a), INDEX b (b)) ENGINE=InnoDB;
INSERT INTO t1(a,b) VALUES (1,1), (2,2), (3,2);
EXPLAIN SELECT * FROM t1 WHERE b=2 ORDER BY a ASC;
id 1
select_type SIMPLE
table t1
type ref
possible_keys b
key b
key_len 5
ref const
rows 1
Extra Using where; Using index
SELECT * FROM t1 WHERE b=2 ORDER BY a ASC;
a b
2 2
3 2
EXPLAIN SELECT * FROM t1 WHERE b=2 ORDER BY a DESC;
id 1
select_type SIMPLE
table t1
type ref
possible_keys b
key b
key_len 5
ref const
rows 1
Extra Using where; Using index
SELECT * FROM t1 WHERE b=2 ORDER BY a DESC;
a b
3 2
2 2
EXPLAIN SELECT * FROM t1 ORDER BY b ASC, a ASC;
id 1
select_type SIMPLE
table t1
type index
possible_keys NULL
key b
key_len 5
ref NULL
rows 3
Extra Using index
SELECT * FROM t1 ORDER BY b ASC, a ASC;
a b
1 1
2 2
3 2
EXPLAIN SELECT * FROM t1 ORDER BY b DESC, a DESC;
id 1
select_type SIMPLE
table t1
type index
possible_keys NULL
key b
key_len 5
ref NULL
rows 3
Extra Using index
SELECT * FROM t1 ORDER BY b DESC, a DESC;
a b
3 2
2 2
1 1
EXPLAIN SELECT * FROM t1 ORDER BY b ASC, a DESC;
id 1
select_type SIMPLE
table t1
type index
possible_keys NULL
key b
key_len 5
ref NULL
rows 3
Extra Using index; Using filesort
SELECT * FROM t1 ORDER BY b ASC, a DESC;
a b
1 1
3 2
2 2
EXPLAIN SELECT * FROM t1 ORDER BY b DESC, a ASC;
id 1
select_type SIMPLE
table t1
type index
possible_keys NULL
key b
key_len 5
ref NULL
rows 3
Extra Using index; Using filesort
SELECT * FROM t1 ORDER BY b DESC, a ASC;
a b
2 2
3 2
1 1
DROP TABLE t1;
End of 5.0 tests
CREATE TABLE `t2` (
`k` int(11) NOT NULL auto_increment,

8
sql/sql_select.cc
View file

@ -12306,6 +12306,12 @@ static int test_if_order_by_key(ORDER *order, TABLE *table, uint idx,
for (; const_key_parts & 1 ; const_key_parts>>= 1)
key_part++;
/*
The primary and secondary key parts were all const (i.e. there's
one row). The sorting doesn't matter.
*/
if (key_part == key_part_end && reverse == 0)
DBUG_RETURN(1);
}
else
DBUG_RETURN(0);
@ -12723,7 +12729,7 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
}
DBUG_RETURN(1);
}
if (tab->ref.key_parts < used_key_parts)
if (tab->ref.key_parts <= used_key_parts)
{
/*
SELECT * FROM t1 WHERE a=1 ORDER BY a DESC,b DESC