Search Results for: mysql what is table lock ratio

Profiling MySQL queries from Performance Schema

When optimizing queries and investigating performance issues, MySQL comes with built in support for profiling queries aka SET profiling = 1; . This is already awesome and simple to use, but why the PERFORMANCE_SCHEMA alternative? Because profiling will be removed soon (already deprecated on MySQL 5.6 ad 5.7); the built-in profiling capability can only be enabled per session. This […]

Deep dive into MySQL’s innochecksum tool

One of our Percona Support customers recently reported that Percona XtraBackup failed with a page corruption error on an InnoDB table. The customer thought it was a problem or bug in the Percona XtraBackup tool. After investigation we found that an InnoDB page was actually corrupted and a Percona XtraBackup tool caught the error as […]

Q&A: Multi-threaded Replication in MySQL 5.6 and MySQL 5.7

My webinar “Multi-threaded Replication in MySQL 5.6 and 5.7″ on February 25 generated several excellent questions following the presentation (available here for playback along with the slides). I didn’t have time to answer many of the questions during the session and so in this post I answer all of them. Thanks to everyone who attended! Q: […]

5 free handy tools for monitoring and managing MySQL replication

MySQL Replication is very simple to set up. In this post I’ll discuss its importance and five handy tools for monitoring and managing MySQL replication. What is MySQL Replication? It’s the process of copying the (real-time events) data from one master instance to another slave instance and maintaining the redundant consistent data in a different […]

The future of MySQL quality assurance: Introducing pquery

Being a QA Engineer, how would you feel if you had access to a framework which can generate 80+ crashes – a mix of hitting developer introduced assertions (situations that should not happen), and serious unforeseen binary crashes – for the world’s most popular open source database software – each and ever hour? What if you could […]

MySQL performance implications of InnoDB isolation modes

Over the past few months I’ve written a couple of posts about dangerous debt of InnoDB Transactional History and about the fact MVCC can be the cause of severe MySQL performance issues. In this post I will cover a related topic – InnoDB Transaction Isolation Modes, their relationship with MVCC (multi-version concurrency control) and how […]

The MySQL Query Cache: How it works, plus workload impacts (good and bad)

Query caching is one of the prominent features in MySQL and a vital part of query optimization. It is important to know how it works as it has the potential to cause significant performance improvements – or a slowdown – of your workload. The MySQL query cache is a global one shared among the sessions. It caches […]

How small changes impact complex systems – MySQL example

If you’ve been studying complex systems you know what minor changes might cause consequences of much greater proportions, sometimes causing some effects that are not easily explained at first. I recently ran across a great illustration of such behavior while doing MySQL benchmarks which I thought would be interesting to share. I’m using a very […]

InnoDB crash recovery speed in MySQL 5.6

It has been a while since I have looked at InnoDB crash recovery. A lot has change in the last few years – we have serious crash recovery performance improvements in MySQL 5.5 and MySQL 5.6, we have solid state drives raising as typical high performance IO subsystem and we also have the ability to […]