Vladimir Fedorkov of Sphinx.

Presentation started out with a very nice presentation of candies to all the audience members.

What is Sphinx? Another (C++) daemon on your boxes. Can be queried via API (PHP, Python, etc.) or MySQL-compatible protocol and SQL queries (SphinxQL). Some query examples are in the slides, here’s one about SphinxSE in the KB.

MyISAM FTS is good but becomes slow with half a million documents. InnoDB has FTS now but he’s not tried it (and neither has anyone in the audience to see it compare with MyISAM FTS).

Geographical distance is the distance measuring the surface of the earth (two pairs of float values – latitude, longitude). In Sphinx, there is support for GEODIST(Lat,Long,Lat2,Long2) in Sphinx.

Segments are good for price ranges on a site, date …

Sergey Petrunia of the MariaDB project.

What exactly is not working in MySQL? MySQL is poor at decision support/analytics. With large datasets you need special disk access strategies. Complex queries like insufficient subquery support and big joins are common int he MySQL world.

DBT-3 is used, scale=30, with a 75GB database and run a query “average price of item between a range of dates”. Query time took some 45 minutes to execute. Why? Run iostat -x to see what is going on. See that the CPU is mostly idle, so its an IO-bound load. Next you run SHOW ENGINE INNODB STATUS and you’ll see how many reads per second is happening. Possible solution is to get more RAM or get an SSD (good to speedup OLTP workloads, but analytics over data is probably not viable since SSDs are small and not cheap).

The MySQL/MariaDB …

MySQL HA reloaded – old tricks and cool new tools to guarantee high availability to your MySQL Servers by Ivan Zoratti of SkySQL. This talk is a little longer, so check out: HA Reloaded – many ways to provide High Availability. The slides are already online.

Questions to ask: which level of high availability do I need? Do I require no loss of data? Do I need failover or is switchover enough? Can I provide a reasonable service when a component is down? Remember, five nine’s high availability also means a lot of infrastructure costs.

Other things to clarify: availability vs scalability. HA costs. HA for your entire architecture, not just for your database servers. Review your SLAs.

The best high availability solution …

Stephane Varoqui, Field Services SkySQL, Vlad Fedorkov, Director of PS, Sphinx Inc, Christophe Gesche, LAMP Expert, Delcampe, Herve Seignole, Web Architect, Groupe Pierre & Vacances Center Parcs – this is a big talk!

Pros: Filtering takes place on attributes in separate tables. Rely on the optimizer choice. HASH JOIN can help (MariaDB 5.3). Table elimination can help (MariaDB 5.2). ICP Index Condition Pushdown can help (MariaDB 5.3/MySQL 5.6). Max 80M documents at Pixmania, all queries come in less than 1s using 128GB of RAM (MariaDB 5.2). At PAP.fr, there is 16GB RAM with MariaDB 5.2.

Cons: CPU intensive (replication with many slaves). Need covering indexes to cover various !filter !order. Join & sorting cost on lazy filtering.

The more indexes you have in the system, the more you need to increase the main …

First talk at FOSDEM MySQL Devroom by Oli Sennhauser, of FromDual. Quick notes/liveblog of the talk, plus links from a quick search.

New Release Model: starts with at least in beta quality, milestone releases are RC quality (every 3-6 months), between milestones new features are allowed, GA releases every 12-18 months, no more than 2 releases in active support. There is also MySQL Labs, in where features can make it into a release model, but not necessarily.

Oli’s guess: MySQL 5.6 GA in April 2012 (Collaborate) or June 2012. As a consequence, MySQL 5.0 and MySQL 5.1 will be EOL probably by April this year.

New improvements in partitioning: explicit partition selection, exchanging partitions (good for ETL jobs).

New improvements in InnoDB: InnoDB INFORMATION_SCHEMA has got some new entries. Buffer …

You may not realize it, but in MariaDB 5.2 and earlier and in MySQL up to version 5.5, START TRANSACTION WITH CONSISTENT SNAPSHOT does not give any guarantees of consistency between different storage engines.

For example, suppose you have two transactions which run in parallel:

Transaction T1:

BEGIN;
    SET @t = NOW();
    UPDATE xtradb_table SET a= @t WHERE id = 5;
    UPDATE pbxt_table SET b= @t WHERE id = 5;
    COMMIT;

Transaction T2:

SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
    START TRANSACTION WITH CONSISTENT SNAPSHOT;
    SELECT t1.a, t2.b
      FROM xtradb_table t1 INNER JOIN pbxt_table t2 ON t1.id=t2.id
    WHERE t1.id = 5;

In the above case, it is possible, even with a "consistent" snapshot, to see the changes in a transaction only in InnoDB/XtraDB tables, and not in PBXT tables.

Naturally, it would be much better if the changes were visible no matter the …

Registration for Percona Live: MySQL Conference and Expo is open! The conference is from Tuesday, April 10th through Thursday, April 12th. Early bird pricing ends March 12th, 2012.
Use code PL-pod and save 10% off the early bird prices!.

The 1st Latin American Conference about MySQL, NoSQL and Cloud technologies will be held in Buenos Aires in June. It is called the MariaDB NoSQL & Cloud Latin American Conference and we'll bring you more information as it becomes available.

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Sometimes, I make mistakes. It’s true. That can be difficult for us Systems Engineering-types to say, but I try to distance myself from my ego and embrace the mistakes because I often learn the most from them. ..Blah, blah, school of hard knocks, blah, blah…. Usually my mistakes aren’t big enough to cause any visible impact, but this one took the site out for 10 minutes during a period of peak traffic due to a confluence of events.

Doh!

Here is how it went down…

We have an issue where MySQL table statistics are occasionally getting out of whack, usually after a batch operation. This causes bad explain plans, which in turn cause impossibly slow queries. An ANALYZE TABLE (or even SHOW CREATE INDEX) resolves the issue immediately, but I prefer not get woken up at 4AM by long running query alerts when my family and I are trying to sleep. As a way to work around the issue, we decided to disable InnoDB automatic …

I recently noticed both MariaDB and XtraDB (not MySQL yet) have a (newer) variable query_cache_strip_comments.

This variable is great for those who want to append comments to various queries, but still want the query cache to be able to serve such queries. Unfortunately, with MySQL, this is not currently possible.

In the past, I wrote a post on using MySQL Proxy which described a technique of monitoring queries through the proxy by appending IP addresses to the queries so one could track where they originated from. However, one pitfall to that was the MySQL query cache *does not* ignore the comment and treats them all as different queries (see the user comments for further discussion). (I did subsequently enhance that functionality implementing the …

The MySQL Forums seem to be have been around forever. There are groups for announcements, performance, InnoDB, Cluster, Replication, Certification, Events, questions in German, partitioning, and just under a hundred MySQL related subjects in total. Most folks in the MySQLverse seem to regularly lurk in one or more of the forums. There area great source of information and sometimes humor. But are you using the forums to help build your MySQL mental muscle? Ask yourself how would you solve the problem or how would you guide a junior DBA or developer to fix an issue posted in a forum.

Try reading the groups that are not in your regular reading list. Is there a question in there you can not answer even after a peek at the documentation?

After running MySQL for a few years, it is easy to skip over the problems of novices found in the …