[MDEV-20704] An index on a double column erroneously uses prefix compression Created: 2019-10-01  Updated: 2022-11-04  Resolved: 2019-10-01

Status: Closed
Project: MariaDB Server
Component/s: Data types
Affects Version/s: 5.5, 10.1, 10.2, 10.3, 10.4
Fix Version/s: 10.2.28, 5.5.66, 10.1.42, 10.3.19, 10.4.9

Type: Bug Priority: Major
Reporter: Alexander Barkov Assignee: Alexander Barkov
Resolution: Fixed Votes: 0
Labels: None

Issue Links:
Blocks
blocks MDEV-4912 Data type plugin API version 1 Closed
Problem/Incident
causes MDEV-28727 ALTER TABLE ALGORITHM=NOCOPY does not... Closed
causes MDEV-29481 mariadb-upgrade prints confusing stat... Closed
Relates
relates to MDEV-28822 Table from older version requires tab... Closed
relates to MDEV-29495 Generalize can_convert_xxx() hook eng... Closed

 Description    

CREATE TABLE t1 (
 
  id INT NOT NULL PRIMARY KEY,
 
  d  DOUBLE,
 
  KEY (d)
 
) ENGINE=MyISAM;

Now run myisamchk -d MYSQLD_DATADIR/test/t1:

MyISAM file:         MYSQLD_DATADIR/test/t1
 
Record format:       Fixed length
 
Character set:       latin1_swedish_ci (8)
 
Data records:                    0  Deleted blocks:                 0
 
Recordlength:                   13
 
 
 
table description:
 
Key Start Len Index   Type
 
1   2     4   unique  long                 
2   6     8   multip. double prefix NULL   
DROP TABLE t1;

Notice prefix in the second index.
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