MySQL 8.0 Release Notes
MySQL 8.0 Source Code Documentation
The following options to mysqld can be used to
change the behavior of MyISAM tables. For
additional information, see Section 5.1.7, “Server Command Options”.
Table 16.3 MyISAM Option and Variable Reference
| Name | Cmd-Line | Option File | System Var | Status Var | Var Scope | Dynamic |
|---|---|---|---|---|---|---|
| bulk_insert_buffer_size | Yes | Yes | Yes | Both | Yes | |
| concurrent_insert | Yes | Yes | Yes | Global | Yes | |
| delay_key_write | Yes | Yes | Yes | Global | Yes | |
| have_rtree_keys | Yes | Global | No | |||
| key_buffer_size | Yes | Yes | Yes | Global | Yes | |
| log-isam | Yes | Yes | ||||
| myisam-block-size | Yes | Yes | ||||
| myisam_data_pointer_size | Yes | Yes | Yes | Global | Yes | |
| myisam_max_sort_file_size | Yes | Yes | Yes | Global | Yes | |
| myisam_mmap_size | Yes | Yes | Yes | Global | No | |
| myisam-recover-options | Yes | Yes | ||||
| - Variable: myisam_recover_options | ||||||
| myisam_recover_options | Yes | Global | No | |||
| myisam_repair_threads | Yes | Yes | Yes | Both | Yes | |
| myisam_sort_buffer_size | Yes | Yes | Yes | Both | Yes | |
| myisam_stats_method | Yes | Yes | Yes | Both | Yes | |
| myisam_use_mmap | Yes | Yes | Yes | Global | Yes | |
| skip-concurrent-insert | Yes | Yes | ||||
| - Variable: concurrent_insert | ||||||
| tmp_table_size | Yes | Yes | Yes | Both | Yes |
Set the mode for automatic recovery of crashed
MyISAMtables.Don't flush key buffers between writes for any
MyISAMtable.NoteIf you do this, you should not access
MyISAMtables from another program (such as from another MySQL server or with myisamchk) when the tables are in use. Doing so risks index corruption. Using--external-lockingdoes not eliminate this risk.
The following system variables affect the behavior of
MyISAM tables. For additional information, see
Section 5.1.8, “Server System Variables”.
The size of the tree cache used in bulk insert optimization.
NoteThis is a limit per thread!
The maximum size of the temporary file that MySQL is permitted to use while re-creating a
MyISAMindex (duringREPAIR TABLE,ALTER TABLE, orLOAD DATA). If the file size would be larger than this value, the index is created using the key cache instead, which is slower. The value is given in bytes.Set the size of the buffer used when recovering tables.
Automatic recovery is activated if you start
mysqld with the
--myisam-recover-options option. In
this case, when the server opens a MyISAM
table, it checks whether the table is marked as crashed or whether
the open count variable for the table is not 0 and you are running
the server with external locking disabled. If either of these
conditions is true, the following happens:
The server checks the table for errors.
If the server finds an error, it tries to do a fast table repair (with sorting and without re-creating the data file).
If the repair fails because of an error in the data file (for example, a duplicate-key error), the server tries again, this time re-creating the data file.
If the repair still fails, the server tries once more with the old repair option method (write row by row without sorting). This method should be able to repair any type of error and has low disk space requirements.
If the recovery wouldn't be able to recover all rows from
previously completed statements and you didn't specify
FORCE in the value of the
--myisam-recover-options option,
automatic repair aborts with an error message in the error log:
Error: Couldn't repair table: test.g00pages
If you specify FORCE, a warning like this is
written instead:
Warning: Found 344 of 354 rows when repairing ./test/g00pages
If the automatic recovery value includes
BACKUP, the recovery process creates files with
names of the form
tbl_name-datetime.BAK