September 2, 2014

How to identify and cure MySQL replication slave lag

Here on the Percona MySQL Support team, we often see issues where a customer is complaining about replication delays – and many times the problem ends up being tied to MySQL replication slave lag. This of course is nothing new for MySQL users and we’ve had a few posts here on the MySQL Performance Blog […]

How rows_sent can be more than rows_examined?

When looking at queries that are candidates for optimization I often recommend that people look at rows_sent and rows_examined values as available in the slow query log (as well as some other places). If rows_examined is by far larger than rows_sent, say 100 larger, then the query is a great candidate for optimization. Optimization could […]

Calvin Sun on MySQL at Twitter, Percona Live 2014 and Facebook

Twitter’s Calvin Sun (@Calvinsun2012) is looking forward to the fast-approaching Percona Live MySQL Conference and Expo this April 1-4 in Santa Clara, Calif. He’ll be speaking, yes, but he’s also looking forward to learning from his peers – particularly those at Facebook. Both companies, he explained, are in the rather unique positions of unprecedented rapid […]

MySQL 5.6.10 Optimizer Limitations: Index Condition Pushdown

While preparing the webinar I will deliver this Friday, I ran into a quite interesting (although not very impacting) optimizer issue: a “SELECT *” taking half the time to execute than the same “SELECT one_indexed_column” query in MySQL 5.6.10. This turned into a really nice exercise for checking the performance and inner workings of one […]

How to find MySQL queries worth optimizing ?

One question I often get is how one can find out queries which should be optimized. By looking at pt-query-digest report it is easy to find slow queries or queries which cause the large portion of the load on the system but how do we know whenever there is any possibility to make this query […]

Can we get faster expression handling in MySQL

Andrew from Sphinx continues to work on improving SQL (or SphinxQL) support and now he published benchmarks comparing arithmetic expression handling in Sphinx to one in MySQL. The result ? Sphinx scored 3x to 20x faster. Andrew goes to explain results are not 100% comparable (as we can see in the table results are even […]

Talking MySQL to Sphinx

In the recently released Sphinx version 0.9.9-rc2 there is a support for MySQL wire protocol and SphinxQL – SQL-like language to query Sphinx indexes. This support is currently in its early preview stage but it is still fun to play with. A thing to mention – unlike MySQL Storage Engines, some of which as InfoBright […]

How to estimate query completion time in MySQL

Have you ever run a query in MySQL and wondered how long it’ll take to complete? Many people have had this experience. It’s not a big deal until the query has been running for an hour. Or a day and a half. Just when IS that query going to finish, anyway? There are actually a […]

MySQL Consulting – Being on your own

About half a year have passed since me and Vadim have left MySQL to do MySQL Consulting on our own. Bunch of people have been wondering about our experiences so I thought it would be worth to share it here.

ORDER BY … LIMIT Performance Optimization

Suboptimal ORDER BY implementation, especially together with LIMIT is often the cause of MySQL Performance problems. Here is what you need to know about ORDER BY … LIMIT optimization to avoid these problems ORDER BY with LIMIT is most common use of ORDER BY in interactive applications with large data sets being sorted. On many […]