| Bug #21106 | Compressed MyISAM table is read only and thus truncate should not be possible | ||
|---|---|---|---|
| Submitted: | 18 Jul 2006 8:08 | Modified: | 19 Jul 2006 10:12 |
| Reporter: | Oli Sennhauser | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: Documentation | Severity: | S2 (Serious) |
| Version: | 5.0.22 | OS: | Any (any) |
| Assigned to: | MC Brown | CPU Architecture: | Any |
| Tags: | compressed, myisam, read only, table, truncate | ||
[18 Jul 2006 12:33]
Valeriy Kravchuk
Verfified just as described with 50.25-BK on Linux. I think, current behaviour is correct (TRUNCATE is a kind of DDL statement, like DROP), but this specific case should be properly documented (as a note at http://dev.mysql.com/doc/refman/5.0/en/compressed-format.html, I think).
[19 Jul 2006 10:12]
MC Brown
I've added a note to the page: While a compressed table is read-only, and you cannot therefore update or add rows in the table, DDL (Data Definition Language) operations are still valid. For example, you may still use <literal>DROP</literal> to drop the table, and <literal>TRUNCATE</literal> to empty the table.
Description: A compressed MyISAM table is according to our documentation read only and thus it should IMHO no be possible to be truncated. or At least comment this in our online docu. This is not what (oracle) users expect?!? How to repeat: mysql> flush table test; # myisampack test.MYI Compressing test.MYD: (2632928 records) - Calculating statistics - Compressing file 73.35% Remember to run myisamchk -rq on compressed tables #> myisamchk -rq test.MYI - check record delete-chain - recovering (with sort) MyISAM-table 'test.MYI' Data records: 2632928 - Fixing index 1 - Fixing index 2 - Fixing index 3 - Fixing index 4 - Fixing index 5 mysql> show table status like 'test'\G *************************** 1. row *************************** Name: test Engine: MyISAM Version: 10 Row_format: Compressed Rows: 2632928 Avg_row_length: 9 Data_length: 24554709 Max_data_length: 281474976710655 Index_length: 107433984 Data_free: 0 Auto_increment: NULL Create_time: 2006-07-18 09:55:14 Update_time: 2006-07-18 09:55:26 Check_time: 2006-07-18 09:58:07 Collation: latin1_swedish_ci Checksum: 2523143152 Create_options: Comment: 1 row in set (0.00 sec) mysql> truncate table test; mysql> select * from test; Empty set (0.38 sec) Suggested fix: Eigther fix this (compressed tables are only allowed to drop but not to truncate or delete) or at least write a comment in the docu.