database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-07-27 18:02:13 +03:00
Code Activity

Fixed bug#28404.

Browse Source 
This patch adds cost estimation for the queries with ORDER BY / GROUP BY
and LIMIT. 
If there was a ref/range access to the table whose rows were required
to be ordered in the result set the optimizer always employed this access
though a scan by a different index that was compatible with the required 
order could be cheaper to produce the first L rows of the result set.
Now for such queries the optimizer makes a choice between the cheapest
ref/range accesses not compatible with the given order and index scans
compatible with it.
This commit is contained in:
igor@olga.mysql.com
2007-08-02 12:45:56 -07:00
parent 642b0c00ed
commit cf39429295
14 changed files with 359 additions and 105 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
mysql-test/r/innodb_mysql.result
View File

@ -851,13 +851,13 @@ EXPLAIN SELECT * FROM t1 WHERE b BETWEEN 1 AND 2 ORDER BY a;
id 1
select_type SIMPLE
table t1
type range
type index
possible_keys bkey
key bkey
key_len 5
key PRIMARY
key_len 4
ref NULL
rows 16
Extra Using where; Using index; Using filesort
rows 32
Extra Using where; Using index
SELECT * FROM t1 WHERE b BETWEEN 1 AND 2 ORDER BY a;
a b
1 2
@ -946,13 +946,13 @@ EXPLAIN SELECT * FROM t2 WHERE b=1 ORDER BY a;
id 1
select_type SIMPLE
table t2
type ref
type index
possible_keys bkey
key bkey
key_len 5
ref const
rows 8
Extra Using where; Using index; Using filesort
key PRIMARY
key_len 4
ref NULL
rows 16
Extra Using where; Using index
SELECT * FROM t2 WHERE b=1 ORDER BY a;
a b c
1 1 1