May 21, 2013

Replication in MySQL 5.6: GTIDs benefits and limitations – Part 1

May 21, 2013 By 2 Comments

Global Transactions Identifiers are one of the new features regarding replication in MySQL 5.6. They open up a lot of opportunities to make the life of DBAs much easier when having to maintain servers under a specific replication topology. However you should keep in mind some limitations of the current implementation. This post is the [...]

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More on MySQL transaction descriptors optimization

April 26, 2013 By Leave a Comment

Since my first post on MySQL transaction descriptors optimization introduced in Percona Server 5.5.30-30.2 and a followup by Dimitri Kravchuk, we have received a large number of questions on why the benchmark results in both posts look rather different. We were curious as well, so we tried to answer that question by retrying benchmarks on [...]

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How to recover table structure from InnoDB dictionary

April 22, 2013 By 4 Comments

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 [...]

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Repair MySQL 5.6 GTID replication by injecting empty transactions

March 26, 2013 By 1 Comment

In a previous post I explained how to repair MySQL 5.6 GTID replication using two different methods. I didn’t mention the famous SET GLOBAL SQL_SLAVE_SKIP_COUNTER = n for a simple reason, it doesn’t work anymore if you are using MySQL GTID. Then the question is: Is there any easy way to skip a single transaction? [...]

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MySQL 5.6 vs MySQL 5.5 and the Star Schema Benchmark

March 11, 2013 By 7 Comments

So far most of the benchmarks posted about MySQL 5.6 use the sysbench OLTP workload.  I wanted to test a set of queries which, unlike sysbench, utilize joins.  I also wanted an easily reproducible set of data which is more rich than the simple sysbench table.  The Star Schema Benchmark (SSB) seems ideal for this. [...]

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InnoDB Full-text Search in MySQL 5.6 (part 1)

February 26, 2013 By 1 Comment

I’ve never been a very big fan of MyISAM; I would argue that in most situations, any possible advantages to using MyISAM are far outweighed by the potential disadvantages and the strengths of InnoDB. However, up until MySQL 5.6, MyISAM was the only storage engine with support for full-text search (FTS). And I’ve encountered many [...]

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Percona XtraDB Cluster (PXC): what about GRA_*.log files ?

December 19, 2012 By Leave a Comment

How easy is it to identify and debug Percona XtraDB Cluster replication problem ? If you are using PXC, you may have already seen in your datadirectory several log files starting with GRA_ Those files correspond to a replication failure. That means the slave thread was not able to apply one transaction. For each of [...]

Filed Under: MySQL, Percona Software, XtraDB Cluster

The Optimization That (Often) Isn’t: Index Merge Intersection

December 14, 2012 By 6 Comments

Prior to version 5.0, MySQL could only use one index per table in a given query without any exceptions; folks that didn’t understand this limitation would often have tables with lots of single-column indexes on columns which commonly appeared in their WHERE clauses, and they’d wonder why the EXPLAIN plan for a given SELECT would [...]

Filed Under: Insight for DBAs, Insight for Developers, MySQL

Knowing what pt-online-schema-change will do

November 1, 2012 By 1 Comment

pt-online-schema-change is simple to use, but internally it is complex.  Baron’s webinar about pt-online-schema-change hinted at several of the tool’s complexities.  Consequently, users often want to know before making changes what pt-online-schema-change will do when it runs.  The tool has two options to help answer this question: –dry-run and –print. When ran with –dry-run and –print, pt-online-schema-change changes nothing [...]

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Edge-case behavior of INSERT…ODKU

October 27, 2012 By 6 Comments

A few weeks back, I was working on a customer issue wherein they were observing database performance that dropped through the floor (to the point of an outage) roughly every 4 weeks or so. Nothing special about the environment, the hardware, or the queries; really, the majority of the database was a single table with [...]

Filed Under: Insight for DBAs, Insight for Developers, MySQL
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