July 31, 2014

MySQL 4 to MySQL 5 Upgrade performance regressions

This week I already had two serious performance regression cases when upgrading from MySQL 4.0 and 4.1 to MySQL 5.0. By serious I mean several times performance difference not just 5-10% you often see for simple queries due to generally fatter code. The problem in both cases was MySQL 5.0 broken group commit bug. First […]

MySQL Replication and Slow Queries

I just filed a bug regarding slow queries executed by replication thread are not being logged to the slow query log. This is not a big deal but it is ugly little gotcha which I think few people know about. It is especially bad if you’re using tools to analyze slow query log to find […]

Backport of micro-time patch to mysql 4.1

Taking into account 4.1 tree is still popular and is used on many production servers we decided to make backport of patch to slow-log queries. The patch allows to specify time of slow queries in microseconds and is very helpful in a fight with problematic queries. 4.1 Patch is available here (The original patch was […]

Database problems in MySQL/PHP Applications

Article about database design problems is being discussed by Kristian. Both article itself and responce cause mixed feellings so I decided it is worth commenting: 1. Using mysql_* functions directly This is probably bad but I do not like solutions proposed by original article ether. PEAR is slow as well as other complex conectors. I […]

Percona Server 5.6.17-65.0 is now available

Percona is glad to announce the release of Percona Server 5.6.17-65.0 on May 6th, 2014. Downloads are available here and from the Percona Software Repositories. Based on MySQL 5.6.17, including all the bug fixes in it, Percona Server 5.6.17-65.0 is the current GA release in the Percona Server 5.6 series. All of Percona’s software is […]

Percona Server 5.5.37-35.0 is now available

Percona is glad to announce the release of Percona Server 5.5.37-35.0 on May 6th, 2014 (Downloads are available here and from the Percona Software Repositories). Based on MySQL 5.5.37, including all the bug fixes in it, Percona Server 5.5.37-35.0 is now the current stable release in the 5.5 series. All of Percona‘s software is open-source and free, all the details of the release […]

Visualization tools for pt-query-digest tables

When you process MySQL slow query logs using pt-query-digest you can store samples of each query into query_review table and historical values for review trend analysis into query_review_history table. But it could be difficult to easily browse those tables without a good GUI tool. For the visual browsing of tables created by pt-query-digest you may […]

Percona Testing: Innodb crash / recovery tests available

Not everyone may know this, but there are precious few innodb crash recovery tests available. Some folks have noticed this and asked for something to be done about it, but unfortunately, no tests have been created for the main MySQL branch. The MySQL at Facebook branch has a number of tests that are quite interesting.  […]

Drop table performance

There have been recent discussions about DROP TABLE performance in InnoDB. (You can refer to Peter’s post http://www.mysqlperformanceblog.com/2011/02/03/performance-problem-with-innodb-and-drop-table/ and these bug reports: http://bugs.mysql.com/bug.php?id=51325 and http://bugs.mysql.com/bug.php?id=56332.) It may not sound that serious, but if your workload often uses DROP TABLE and you have a big buffer pool, it may be a significant issue. This can get […]

mk-query-digest, query comments and the query cache

I very much like the fact that MySQL allows you to embed comments into SQL statements. These comments are extremely convenient, because they are written into MySQL log files as part of the query. This includes the general log, the binary log and the slow query log. Maatkit includes tools which interact with these logs, […]