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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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 …

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.

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 […]

The post Follow up on FOSDEM appeared first on Spil Games Engineering.

Thanks to all who attended my webinar yesterday.  The slides and recording are available on the webinar’s page.  I was a bit overwhelmed with the amount of questions that came in and I’ll try to answer them the best I can here.

Q: Does Percona XtraDB Cluster support writing to multiple master?

Yes, it does.  However, locks are not held on all nodes while a transaction is in progress, so there is a possibility for conflicts between simultaneous writes on different nodes.  Certification is the process that Galera uses to protect your data integrity, and the problem is pushed back to the application to handle in the form of deadlock errors.   As long as you understand this and the conditions where you may see more deadlocks (and your application can properly handle them), multi-node …

My students required way to remove all their tables, views, and constraints from a MySQL database (or the alias schema). Since they’re using referential or foreign key constraints, I also wrote one procedure to drop all foreign key constraints from a database. There’s also another to drop views. The final stored procedure calls the procedure that drops foreign keys, then calls the procedure to drop views before dropping all the tables.

Here’s the dropForeignKeys stored procedure:

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-- Provide a log file debugging statement.
SELECT 'DROP PROCEDURE IF EXISTS dropForeignKeys';
 
-- Conditionally drop the procedure.
DROP PROCEDURE IF EXISTS …

In teaching, I had a problem because my students have different base operating systems, like Windows 7, Windows 8, Linux, and Mac OS X. I needed a teaching and lecture platform that would let me teach it all (not to mention support their environments). That meant it had to virtualize any of the following with a portable device:

• Windows 7 or 8 hosting natively an Oracle Database 11g XE, 11g, or 12c and MySQL Database 5.6
• Windows 7 or 8 hosting a Fedora or Oracle Unbreakable Linux VM (3 or 4 GB) with Oracle Database 11g XE, 11g, or 12c and MySQL Database 5.6
• Mac OS X hosting a Fedora or Oracle Unbreakable Linux VM (3 or 4 GB) with Oracle Database 11g XE, 11g, or 12c and MySQL Database 5.6
• Ubuntu hosting a Fedora or Oracle Unbreakable Linux VM (3 or 4 GB) with Oracle Database 11g XE, 11g, or …