November 21, 2014

Indexes in MySQL

MySQL does not always make a right decision about indexes usage. Condsider a simple table:

; 250001 (V1)

; 83036 (V2) (execution time = 110 ms) That is index selectivity by condition (ID1=1) is V2/V1 = 0.3321 or 33.21% It is said (e.g. book “SQL Tuning”) if selectivity over 20% then a full table […]

InnoDB memory usage

There are many questions how InnoDB allocates memory. I’ll try to give some explanation about the memory allocation at startup. Some important constants: NBLOCKS=count of block in innodb_buffer_pool = innodb_buffer_pool_size / 16384 OS_THREADS= if (innodb_buffer_pool_size >= 1000Mb) = 50000 else if (innodb_buffer_pool_size >= 8Mb) = 10000 else = 1000 (it’s true for *nixes, for Windows […]

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 […]

Sys Schema for MySQL 5.6 and MySQL 5.7

Performance Schema (P_S) has been available since MySQL 5.5, more than 4 years ago. It is still difficult to see production servers with P_S enabled, even with MySQL 5.6 where the feature is enabled by default. There have been several complaints like the overhead, that the fix is a work in progress, and the ease […]

Backup and restore of MySQL to OpenStack Swift

MySQL database usage is popular in OpenStack. Core OpenStack services for Compute (Nova), Storage (Cinder), Neutron (Networking), Image (Glance) and Identity (Keystone) all use MySQL database. MySQL – as the world’s most popular database, runs inside OpenStack Virtual Machines and serves as database backend to OpenStack cloud based applications. The MySQL instances can be configured […]

OpenStack users shed light on Percona XtraDB Cluster deadlock issues

I was fortunate to attend an Ops discussion about databases at the OpenStack Summit Atlanta this past May as one of the panelists. The discussion was about deadlock issues OpenStack operators see with Percona XtraDB Cluster (of course this is applicable to any Galera-based solution). I asked to describe what they are seeing, and as […]

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 […]

Percona XtraDB Cluster 5.6.15-25.5 is now available

Percona is glad to announce the new release of Percona XtraDB Cluster 5.6 on March 20th 2014. Binaries are available from downloads area or from our software repositories. Based on Percona Server 5.6.15-63.0 including all the bug fixes in it, Galera Replicator 3.4 and on Codership wsrep API 25.5 is now the current General Availability […]

Percona Server 5.5.36-34.0 is now available

Percona is glad to announce the release of Percona Server 5.5.36-34.0 on March 10th, 2014 (Downloads are available here and from the Percona Software Repositories). Based on MySQL 5.5.36, including all the bug fixes in it, Percona Server 5.5.36-34.0 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 […]

The MySQL ARCHIVE storage engine – Alternatives

In my previous post I pointed out that the existing ARCHIVE storage engine in MySQL may not be the one that will satisfy your needs when it comes to effectively storing large and/or old data. But are there any good alternatives? As the primary purpose of this engine is to store rarely accessed data in disk […]