Tag: queries

Software

ProxySQL Releasing ProxySQL 1.4.6

Proudly announcing the release of the latest stable release of ProxySQL 1.4.4 as of the 1st of February 2018. ProxySQL is a high performance, high availability, protocol aware proxy for MySQL. It can be downloaded here, and freely usable and accessible according to GPL license. ProxySQL 1.4.6 includes a number of important improvements and bug …

Miscellaneous

ProxySQL | Compiling ProxySQL on FreeBSD

Compiling ProxySQL 1.4.6 on FreeBSD 11.1 FreeBSD is the operating system of choice for many MySQL installations and a topic that often comes up in the ProxySQL Google Forums as well as the ProxySQL Github Issue Tracker is related to ProxySQL on FreeBSD. An official package for FreeBSD (and BSD in general) is not available …

Performance

Four Ways MySQL Executes GROUP BY

In this blog post, I’ll look into four ways MySQL executes GROUP BY.  In my previous blog post, we learned that indexes or other means of finding data might not be the most expensive part of query execution. For example, MySQL GROUP BY could potentially be responsible for 90% or more of the query execution time.  …

Performance

MySQL Query Performance: Not Just Indexes

  In this blog post, I’ll look at whether optimizing indexing is always the key to improving MySQL query performance (spoiler, it isn’t). As we look at MySQL query performance, our first concern is often whether a query is using the right indexes to retrieve the data. This is based on the assumption that finding the data …

Performance

Using MySQL 5.7 Generated Columns to Increase Query Performance

  In this blog post, we’ll look at ways you can use MySQL 5.7 generated columns (or virtual columns) to improve query performance. Introduction About two years ago I published a blog post about Generated (Virtual) Columns in MySQL 5.7. Since then, it’s been one of my favorite features in the MySQL 5.7 release. The reason …

Miscellaneous, Software

Enhanced replication monitoring in ProxySQL 1.4.4

ProxySQL and pt-heartbeat The Percona toolkit provides a very useful script for more accurate replication lag monitoring called pt-heartbeat. The pt-heartbeat script provides replication lag metrics based on actual data that has been replicated and is more accurate than the Seconds_Behind_Master metrics gathered from the output of SHOW SLAVE STATUS. Seconds_Behind_Master relies purely on system …

Performance, Troubleshooting

Improved JOIN Order by Taking Condition Filter Effect into Account

One of the major challenges of query optimizers is to correctly estimate how many rows qualify from each table of a join. If the estimates are wrong, the optimizer may choose a non-optimal join order. Before MySQL 5.7, the estimated number of rows from a table only took into account the conditions from the WHERE …

Troubleshooting

Useful queries on MySQL information_schema

MySQL information_schema comes with useful information about the database instance, status, … etc. which is needed for daily DBA work. There are some simple queries on the information_schema that I use on my daily basis in which I’m writing this post for my reference and maybe a good reference for someone else too … Finding …