To recover a dropped or corrupt table with Percona Data Recovery Tool for InnoDB you need two things: media with records(ibdata1, *.ibd, disk image, etc.) and a table structure. Indeed, there is no information about the table structure in an InnoDB page. Normally we either recover the structure from .frm files or take it from [...]
MySQL 5.6: Improvements in the Nutshell
January 27, 2013 By 16 Comments
Preparing for my talk for Percona MySQL University in Raleigh,NC, Tuesday 29th of January I have created the outline of improvements available in MySQL 5.6 which I thought was worth sharing to give a feel for how massive work have been done for this release in variety of areas. I’m sure the list is not [...]
Recovery after DROP & CREATE
August 22, 2012 By 1 Comment
In a very popular data loss scenario a table is dropped and empty one is created with the same name. This is because mysqldump in many cases generates the “DROP TABLE” instruction before the “CREATE TABLE”:
1 2 3 4 5 6 7 8 9 10 11 12 | DROP TABLE IF EXISTS `actor`; /*!40101 SET @saved_cs_client = @@character_set_client */; /*!40101 SET character_set_client = utf8 */; CREATE TABLE `actor` ( `actor_id` smallint(5) unsigned NOT NULL AUTO_INCREMENT, `first_name` varchar(45) NOT NULL, `last_name` varchar(45) NOT NULL, `last_update` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, PRIMARY KEY (`actor_id`), KEY `idx_actor_last_name` (`last_name`) ) ENGINE=InnoDB AUTO_INCREMENT=201 DEFAULT CHARSET=utf8; /*!40101 SET character_set_client = @saved_cs_client */; |
If there were no subsequent CREATE TABLE the recovery would be trivial. Index_id of the PRIMARY index of [...]
Recovery deleted ibdata1
August 10, 2012 By 9 Comments
Recently I had a case when a customer deleted the InnoDB main table space – ibdata1 – and redo logs – ib_logfile*. MySQL keeps InnoDB files open all the time. The following recovery technique is based on this fact and it allowed to salvage the database. Actually, the files were deleted long time ago – [...]
Why ALTER TABLE shows as two transactions in SHOW ENGINE INNODB STATUS
July 1, 2012 By 4 Comments
When executing an ALTER TABLE, InnoDB (and XtraDB) will create two InnoDB transactions: One transaction is created when the table being ALTERed is locked by the server. This will show up as something like “TABLE LOCK table `schema`.`table_name` trx id XXXX lock mode S” in SHOW ENGINE INNODB STATUS. Another is created when adding or [...]
Percona welcomes Drizzle 7.1
April 10, 2012 By Leave a Comment
The Drizzle team has published the first Drizzle 7.1 stable release. The announcement on the Drizzle blog covers some of the major improvements in this release over the previous stable release, Drizzle 7.0. I plan to write a variety of blog posts on each of the new features over the coming weeks. Major features include: Multi [...]
Troubleshooting MySQL Memory Usage
March 21, 2012 By 5 Comments
One of the most painful troubleshooting tasks with MySQL is troubleshooting memory usage. The problem usually starts like this – you have configured MySQL to use reasonable global buffers, such as innodb_buffer_size, key_buffer_size etc, you have reasonable amount of connections but yet MySQL takes much more memory than you would expect, causing swapping or other [...]
Optimizing InnoDB for creating 30,000 tables (and nothing else)
December 22, 2011 By 5 Comments
Once upon a time, it would have been considered madness to even attempt to create 30,000 tables in InnoDB. That time is now a memory. We have customers with a lot more tables than a mere 30,000. There have historically been no tests for anything near this many tables in the MySQL test suite. So, [...]
Percona Server 5.5.18-23.0: Now with Group Commit!
December 19, 2011 By 3 Comments
Percona is glad to announce the release of Percona Server 5.5.18-23.0 on December 19th, 2011 (Downloads are available here and from the Percona Software Repositories). Based on MySQL 5.5.18, including all the bug fixes in it, Percona Server 5.5.18-23.0 is now the current stable release in the 5.5 series. All of Percona ‘s software is open-source and free, all the details of the release can [...]
Beware the Innodb Table Monitor
November 29, 2011 By 2 Comments
As I stated in my last post, I decided to use the Innodb Table monitor to diagnose an Index count mismatch error a customers found in their mysqld.err log to verify if the problem still existed. The Innodb Table Monitor has existed for basically forever in Innodb (the MySQL manual discusses it back in the 4.1 [...]
