August 31, 2014

InnoDB scalability issues due to tables without primary keys

Each day there is probably work done to improve performance of the InnoDB storage engine and remove bottlenecks and scalability issues. Hence there was another one I wanted to highlight: Scalability issues due to tables without primary keys This scalability issue is caused by the usage of tables without primary keys. This issue typically shows […]

Percona XtraDB Cluster: Setting up a simple cluster

Percona XtraDB Cluster (PXC) is different enough from async replication that it can be a bit of a puzzle how to do things the Galera way.  This post will attempt to illustrate the basics of setting up 2 node PXC cluster from scratch. Requirements Two servers (could be VMs) that can talk to each other. […]

Your troubles are over, pt-heartbeat 2.1

Poor pt-heartbeat 2.1: it was perfectly fine through Percona Toolkit 2.1.7, but it’s had a rough life since. Its troubles are finally over as of Percona Toolkit 2.1.10. At a conference recently, a user joked to me that “Percona Toolkit is awesome, but you really broke pt-heartbeat.” It’s true, and if you haven’t heard or […]

Percona Toolkit 2.2.2 released; bug fixes include pt-heartbeat & pt-archiver

During the Percona Live MySQL Conference & Expo 2013 the week before last, we quietly released Percona Toolkit 2.2.2 with a few bug fixes: pt-archiver –bulk-insert may corrupt data pt-heartbeat –utc –check always returns 0 pt-query-digest 2.2 prints unwanted debug info on tcpdump parsing errors pt-query-digest 2.2 prints too many string values Some tools don’t […]

Full Text Search Webinar Questions Followup

I presented a webinar this week to give an overview of several Full Text Search solutions and compare their performance.  Even if you missed the webinar, you can register for it, and you’ll be emailed a link to the recording. During my webinar, a number of attendees asked some good questions.  Here are their questions and my […]

Flexviews – part 3 – improving query performance using materialized views

Combating “data drift” In my first post in this series, I described materialized views (MVs). An MV is essentially a cached result set at one point in time. The contents of the MV will become incorrect (out of sync) when the underlying data changes. This loss of synchronization is sometimes called drift. This is conceptually […]

Paul McCullagh answers your questions about PBXT

Following on from our earlier announcement, Paul McCullagh has responded with the answers to your questions – as well as a few I gathered from other Percona folks, and attendees of OpenSQL Camp. Thank you Paul! What’s the “ideal” use case for the PBXT engine, and how does it compare in performance?  When would I […]

A rule of thumb for choosing column order in indexes

I wanted to share a little rule of thumb I sometimes use to decide which columns should come first in an index. This is not specific to MySQL, it’s generally applicable to any database server with b-tree indexes. And there are a bunch of subtleties, but I will also ignore those for the sake of […]

Query_cache and column level privileges

Recently we were puzzled by question how query_cache works with column level privileges. The question was appeared as we discovered function query_cache_send_result_to_client is called before real parsing of query, so at the moment of execution the query_cache is not able to know which columns are accessed. Looking into source code I found out that in […]

GROUP_CONCAT useful GROUP BY extension

(There is an updated version of this post here) MySQL has useful extention to the GROUP BY operation: function GROUP_CONCAT: GROUP_CONCAT(expr) – This function returns a string result with the concatenated non-NULL values from a group. Where it can be useful?