May 21, 2013

Understanding the maximum number of columns in a MySQL table

April 8, 2013 By 5 Comments

This post was initially going to be two sets of polls: “What is the maximum number of columns in MySQL?” and “What is the minimum maximum number of columns in MySQL?”. Before you read on, ponder those questions and come up with your own answers… and see if you’re right or can prove me wrong! [...]

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InnoDB Full-text Search in MySQL 5.6: Part 2, The Queries!

March 4, 2013 By 7 Comments

This is part 2 in a 3 part series. In part 1, we took a quick look at some initial configuration of InnoDB full-text search and discovered a little bit of quirky behavior; here, we are going to run some queries and compare the result sets. Our hope is that the one of two things [...]

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How to obtain the “LES” (Last Executed Statement) from an Optimized Core Dump?

September 9, 2012 By 9 Comments

Ever ran into a situation where you saw “some important variable you really needed to know about=<optimized out>” while debugging?

Filed Under: Insight for DBAs, Insight for Developers, MySQL

Data compression in InnoDB for text and blob fields

May 30, 2012 By 2 Comments

Have you wanted to compress only certain types of columns in a table while leaving other columns uncompressed? While working on a customer case this week I saw an interesting problem where a table had many heavily utilized TEXT fields with some read queries exceeding 500MB (!!), and stored in a 100GB table. In this [...]

Filed Under: Insight for DBAs, Insight for Developers, MySQL, Percona Software

Troubleshooting MySQL Memory Usage

March 21, 2012 By 5 Comments

One of the most painful troubleshooting tasks with MySQL is troubleshooting memory usage. The problem usually starts like this – you have configured MySQL to use reasonable global buffers, such as innodb_buffer_size, key_buffer_size etc, you have reasonable amount of connections but yet MySQL takes much more memory than you would expect, causing swapping or other [...]

Filed Under: Insight for DBAs, MySQL

Shard-Query EC2 images available

May 11, 2011 By 2 Comments

Infobright and InnoDB AMI images are now available There are now demonstration AMI images for Shard-Query. Each image comes pre-loaded with the data used in the previous Shard-Query blog post. The data in the each image is split into 20 “shards”. This blog post will refer to an EC2 instances as a node from here [...]

Filed Under: MySQL

Innodb row size limitation

April 7, 2011 By 12 Comments

I recently worked on a customer case where at seemingly random times, inserts would fail with Innodb error 139. This is a rather simple problem, but due to it’s nature, it may only affect you after you already have a system running in production for a while.

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Extending Index for Innodb tables can hurt performance in a surprising way

May 22, 2010 By 10 Comments

One schema optimization we often do is extending index when there are queries which can use more key part. Typically this is safe operation, unless index length increases dramatically queries which can use index can also use prefix of the new index are they ? It turns there are special cases when this is not [...]

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Joining on range? Wrong!

May 17, 2010 By 10 Comments

The problem I am going to describe is likely to be around since the very beginning of MySQL, however unless you carefully analyse and profile your queries, it might easily go unnoticed. I used it as one of the examples in our talk given at phpDay.it conference last week to demonstrate some pitfalls one may [...]

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Multi Column indexes vs Index Merge

September 19, 2009 By 31 Comments

The mistake I commonly see among MySQL users is how indexes are created. Quite commonly people just index individual columns as they are referenced in where clause thinking this is the optimal indexing strategy. For example if I would have something like AGE=18 AND STATE=’CA’ they would create 2 separate indexes on AGE and STATE [...]

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