MySQL 5.5.36 was recently released (it is the latest MySQL 5.5, is GA), and is available for download here:

http://dev.mysql.com/downloads/mysql/5.5.html

I was reading through the changelogs to review the changes and fixes, and to summarize, I must say this release is mostly uneventful.

There was one new feature added (for building, so not really applicable to everyone), and only 17 bugs fixed.

The new feature is this:

• CMake now supports a -DTMPDIR=dir_name option to specify the default tmpdir value. If unspecified, the value defaults to P_tmpdir in . Thanks to Honza Horak for the patch. (Bug #68338, Bug #16316074)

Out of the 17 bugs, there was only 1 I thought worth mentioning (because it is a wrong results bug):

• COUNT(DISTINCT) sometimes produced an incorrect result when the last read row …

Ever found yourself working on a MySQL server where root’s password is unavailable? It has happened to me a few times, always because the person who set up the DB left the place long ago, and this information was not documented anywhere. If you have root access to the OS, MySQL lets you restart the … Continue reading Recovering MySQL access →

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3. …

MySQL 5.6 has been GA for just over a year now. See MySQL 5.6.10 Release Notes.  Congratulations on your birthday! That is quite a long time. I was using it earlier in production because it worked and could do things that 5.5 could not do, but earlier versions were to use at your own risk, and indeed if prodded incorrectly would fall on the floor. That is fair enough because they were work in progress, yet if you poked them the right way they did a very good job.  Those dev versions have been long since upgraded which is good so they do not need quite as much care and attention.

So from where I see 5.6 it works very well. One big change that has made a large difference but which I think a lot of people may not really understand or use is the …

Now it’s time to setup proper monitoring to avoid unpleasant surprises in future.

There are two major problems the monitoring solves: alerting and trending. Alerting is to notify a responsible person about some major event like service stopped working. Trending is to track the change of something over time – disk or memory usage over time, replication lag etc.

This post will be about alerting with Nagios.

The major problem with most of Nagios setups I’ve seen is excessive amount of false positives. This kills whole idea of monitoring. The matter is when an admin gets a false alert they tend to mute it, explicitly or implicitly. They either filter alerts out or don’t treat them seriously. In general case the alert must be worth to wake up the admin in the middle of the night. If the alert isn’t worth as much the real problem will be ignored sooner or …

During FOSDEM PGDay I watched the "Indexes: The neglected performance all-rounder" talk by Markus Winand. Both his talk and the "SQL Performance Explained" book (which is also available online) are great.

The conclusion of the talk is that we should put more effort in carefully designing indexes. But how can we make sure the indexes are really used now and in the future? We need to write some tests for it.

So I wrote a small Python script to test index usage per query. This uses the JSON explain format available in MySQL 5.6. It's just a proof-of-concept so don't expect too much of it yet (but please sent pull requests!).

A short example:

#!/usr/bin/python3
import indextest

 …

The temporal datatypes ‘TIME/DATETIME/TIMESTAMP’ supports fractional values starting from MySQL 5.6.4 version. Hence the storage requirement and encoding differs in comparison to pre- MySQL 5.6.4 temporal datatypes.

As mentioned in the section ‘Upgrading from MySQL 5.5 to 5.6′,

http://dev.mysql.com/doc/refman/5.6/en/upgrading-from-previous-series.html

Once you have imported the pre-MySQL 5.6.4 tables, ‘ALTER TABLE’ allows creation of tables containing temporal columns of both mysql-5.5 and mysql-5.6 format.

As noted in the documentation, the disadvantages of having such tables are:

• Recreating tables having both 5.5 and 5.6 temporals becomes tedious process when the metadata file(.frm) for the table is unavailable. This would involve recreating the table having the old temporal columns using 5.5 server instance and then adding the 5.6 temporal columns using 5.6 server instance.
…

It's my pleasure to be presenting at SCaLE 12X on the subject of real-time data loading from MySQL to Hadoop.  This is the first public talk on work at Continuent that enables Tungsten Replicator to move transactions from MySQL to HDFS (Hadoop Distributed File System).  I will explain how replication to Hadoop works, how to set it up, and offer a few words on constructing views of MySQL data using tools like Hive.

As usual with replication everything we are doing on Hadoop replication is open source.  Builds and documentation will be publicly available …

The binary and source versions of MySQL Cluster 7.3.4 have now been made available at http://www.mysql.com/downloads/cluster/.

A description of all of the changes (fixes) that have gone into MySQL Cluster 7.3.4 (compared to 7.3.3) is available from the 7.3.4 Change log.

In this blog post (which was inspired by Adrian Nuta’s recent talk about Sphinx at FOSDEM), we go through some more of the differences between MySQL fulltext search and Sphinx. People frequently ask us questions along these lines, so we decided another blog post on the subject would be worthwhile. Check it out! Introduction This [...]

After my presentation at FOSDEM I got a few questions regarding our Galera implementation and why we did things the way we want. First of all, the slides: Spil Games @ FOSDEM: Galera Replicator IRL from spil-engineering Second of all, the questions I got: Q: Why first copy all the data to a new MySQL […]

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