October 30, 2014

Facebook MySQL database engineers ready for Percona Live London 2014

With 1.28 billion active users, Facebook MySQL database engineers are active and extremely valuable contributors to the global MySQL community. So naturally they are also active participants of Percona Live MySQL conferences! And next week’s Percona Live London 2014 (Nov. 3-4) is no exception. (Register now and use the promotional code “Facebook” to save £30!) […]

How to deal with MySQL deadlocks

A deadlock in MySQL happens when two or more transactions mutually hold and request for locks, creating a cycle of dependencies. In a transaction system, deadlocks are a fact of life and not completely avoidable. InnoDB automatically detects transaction deadlocks, rollbacks a transaction immediately and returns an error. It uses a metric to pick the […]

Using MySQL 5.6 Global Transaction IDs (GTIDs) in production: Q&A

Thank you to all of you who attended my webinar last week about Global Transaction IDs (GTIDs), which were introduced in MySQL 5.6 to make the reconfiguration of replication straightforward. If you missed my webinar, you can still listen to the recording and download the sides (free). We had a lot of questions during the […]

Examining the TokuDB MySQL storage engine file structure

As we know different storage engines in MySQL have different file structures. Every table in MySQL 5.6 must have a .frm file in the database directory matching the table name. But where the rest of the data resides depends on the storage engine. For MyISAM we have .MYI and .MYD files in the database directory […]

TIMESTAMP Columns, Amazon RDS 5.6, and You

This comes from an issue that I worked on recently, wherein a customer reported that their application was working fine under stock MySQL 5.6 but producing erroneous results when they tried running it on Amazon RDS 5.6. They had a table which, on the working server, contained two TIMESTAMP columns, one which defaulted to CURRENT_TIMESTAMP […]

Using MySQL 5.6 Performance Schema in multi-tenant environments

Hosting a shared MySQL instance for your internal or external clients (“multi-tenant”) was always a challenge. Multi-tenants approach or a “schema-per-customer” approach is pretty common nowadays to host multiple clients on the same MySQL sever. One of issues of this approach, however, is the lack of visibility: it is hard to tell how many resources (queries, disk, […]

GTIDs in MySQL 5.6: New replication protocol; new ways to break replication

One of the MySQL 5.6 features many people are interested in is Global Transactions IDs (GTIDs). This is for a good reason: Reconnecting a slave to a new master has always been a challenge while it is so trivial when GTIDs are enabled. However, using GTIDs is not only about replacing good old binlog file/position […]

Many-table joins in MySQL 5.6

I recently worked on an uncommon slow query: less than 100 rows were read and returned, the whole dataset was fitting in memory but the query took several seconds to run. Long story short: the query was a join involving 21 tables, running on MySQL 5.1. But by default MySQL 5.1 is not good at […]

Percona Replication Manager (PRM) now supporting 5.6 GTID

Over the last few days, I integrated the MySQL 5.6 GTID version of the Percona Replication Manager (PRM) work of Frédéric Descamps, a colleague at Percona. The agent supports the GTID replication mode of MySQL 5.6 and if the master suffers a hard crash, it picks the slave having applied the highest transaction ID from […]

Multiple column index vs multiple indexes with MySQL 5.6

A question often comes when talking about indexing: should we use multiple column indexes or multiple indexes on single columns? Peter Zaitsev wrote about it back in 2008 and the conclusion then was that a multiple column index is most often the best solution. But with all the recent optimizer improvements, is there anything different with […]