database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-07-29 05:21:33 +03:00
Code Activity

MDEV-30324: Wrong result upon SELECT DISTINCT ... WITH TIES

Browse Source 
WITH TIES would not take effect if SELECT DISTINCT was used in a
context where an INDEX is used to resolve the ORDER BY clause.

WITH TIES relies on the `JOIN::order` to contain the non-constant
fields to test the equality of ORDER BY fiels required for WITH TIES.

The cause of the problem was a premature removal of the `JOIN::order`
member during a DISTINCT optimization. This lead to WITH TIES code assuming
ORDER BY only contained "constant" elements.

Disable this optimization when WITH TIES is in effect.

(side-note: the order by removal does not impact any current tests, thus
it will be removed in a future version)

Reviewed by: monty@mariadb.org
This commit is contained in:
Vicențiu Ciorbaru
2023-02-15 16:20:25 +02:00
parent d2b773d913
commit 4afa3b64c4
3 changed files with 48 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
mysql-test/main/fetch_first.test
View File

@ -1059,3 +1059,22 @@ SELECT a FROM t ORDER BY a FETCH FIRST 2 ROWS WITH TIES;
# Cleanup
DROP TABLE t;
--echo #
--echo # MDEV-30324: Wrong result upon SELECT DISTINCT .. WITH TIES using index
--echo #
CREATE TABLE t1 (a int, b char(3), KEY (a));
INSERT INTO t1 VALUES (2,'foo'),(3,'bar'),(3,'bar'),(3,'zzz');
EXPLAIN SELECT DISTINCT a, b FROM t1 ORDER BY a FETCH FIRST 1 ROWS WITH TIES;
--sorted_result
SELECT DISTINCT a, b FROM t1 ORDER BY a FETCH FIRST 1 ROWS WITH TIES;
EXPLAIN SELECT DISTINCT a, b FROM t1 ORDER BY a FETCH FIRST 2 ROWS WITH TIES;
--sorted_result
SELECT DISTINCT a, b FROM t1 ORDER BY a FETCH FIRST 2 ROWS WITH TIES;
EXPLAIN SELECT DISTINCT a, b FROM t1 ORDER BY a FETCH FIRST 3 ROWS WITH TIES;
--sorted_result
SELECT DISTINCT a, b FROM t1 ORDER BY a FETCH FIRST 3 ROWS WITH TIES;
# Cleanup
DROP TABLE t1;