This post explains on the usage of mysql_repair_threads for repairing myisam table & the processlist status Repair with N threads
MySQL 5.5.40 was recently released (it is the latest MySQL 5.5, is GA), and is available for download here:
This release, similar to the last 5.5 release, is mostly uneventful.
There were 0 “Functionality Added or Changed” bugs this time, and 18 bugs overall fixed.
Out of the 18 bugs, most seemed rather minor or obscure, but there are 3 I think are worth noting (all 3 are InnoDB-related, regressions, and serious if you encounter them, so best to be aware of them):
- InnoDB: An ALTER TABLE … ADD FOREIGN KEY operation could cause a serious error. (Bug #19471516, Bug #73650)
- InnoDB: With a transaction isolation level less than or equal to READ COMMITTED, gap locks …
MySQL organizes all the data as tables, irrespective of storage
engine used. If you are using MySQL with InnoDB tables, these
tables might get corrupt due to hardware faults, unexpected power
failure, MySQL code errors, kernel bugs and other similar
reasons. In such cases, InnoDB will typically give some errors
indicating table corruption. As a data restoration source, you
will need to use your latest database backup. But in case if
backup fails to restore required information or doesn’t exist,
you should scan your damaged database using third-party MySQL
Repair or MySQL Recovery tools.
You might encounter the similar error message while accessing an InnoDB table:
“#1033 - Incorrect information in file: '"table name" .frm”
MySQL crashes after you receive this error message.
Cause: You receive this error message if …
Bugzilla is a web-based bug tracking and testing application that
is used by many software development companies. It extensively
various databases including MySQL for its backend support
especially because both of these applications are freely
available. Although this tool runs pretty fine in most cases, it
can get stalled when the some of the MySQL tables get corrupt. In
such cases, you are unable to perform various tasks on the
database. You can use the 'myisamchk' command with different
parameters to repair MySQL database. If it does not work, then
you should use a professional MySQL
recovery software to recover MySQL database.
Discussing a similar situation in Bugzilla, consider you get the following error message while generating a bugs report:
"undef error - DBD::mysql::db selectrow_array failed: Table 'attach_data' is
marked as crashed …
MySQL is the most popular open-source database in the world. It
has the distinction of being the only database that is used in
every continent. Yes, even Antartica!!! The reasons for such
popularity is its availability, performance, robustness, etc. It
provides three types of database engines, MyISAM, InnoDB, and
MySQL Archive. Out of these, the MyISAM table is the default
table type. It is fast, simple, and allows full-text searching.
Although it is reliable, it can become corrupt and, thus,
inaccessible following a system crash. You should use appropriate
corrective measures to repair MySQL database. However, if you are
not able to do so then you should use a third-party MySQL
recovery software to do so.
Consider a scenario wherein you have MySQL 5.0.22 database running in your system. You use it for MediaWiki installation that is reported as corrupt. When you try to repair the table, the following error message is displayed: