[MDEV-27330] Wrong sorting order with DESC index and empty strings in MyISAM/Aria table Created: 2021-12-21  Updated: 2022-01-26  Resolved: 2022-01-26

Status: Closed
Project: MariaDB Server
Component/s: Server
Affects Version/s: N/A
Fix Version/s: 10.8.1

Type: Bug Priority: Critical
Reporter: Elena Stepanova Assignee: Sergei Golubchik
Resolution: Fixed Votes: 0
Labels: None

Issue Links:
Problem/Incident
is caused by MDEV-13756 Implement descending index: KEY (a DE... Closed
Relates
relates to MDEV-27303 Table corruption after insert into a ... Closed

 Description    

CREATE TABLE t (id int, c char(128) NOT NULL, KEY (c DESC)) ENGINE=MyISAM CHARSET latin1;
 
INSERT INTO t VALUES (1,''),(2,'foo'),(3,''),(4,'bar');
 
 
 
SELECT c FROM t ORDER BY c;
 
 
 
# Cleanup
 
DROP TABLE t;

preview-10.8-MDEV-13756-desc-indexes 47c18283

 
MariaDB [test]> SELECT c FROM t ORDER BY c;
 
+-----+
 
| c   |
 
+-----+
 
| bar |
 
| foo |
 
|     |
 
|     |
 
+-----+
 
4 rows in set (0.000 sec)

So, the empty strings go last, contrary to the expectation.
Reproducible with MyISAM and Aria.
Not reproducible with InnoDB.

 Comments   
Comment by Sergei Golubchik [ 2021-12-21 ]

pushed into preview-10.8-MDEV-13756-desc-indexes

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