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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/r/innodb_mysql.result:
  Bug #31001: test case
mysql-test/t/innodb_mysql.test:
  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 17:43:14 +03:00
parent aa5da0fc9e
commit ad496be063
3 changed files with 127 additions and 1 deletions
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97
mysql-test/r/innodb_mysql.result
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@ -1114,4 +1114,101 @@ c b
3 1
3 2
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