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 […]
Read MoreDuring last couple of months I had number of consulting projects with MySQL Query Cache being source of serious problems. One would see queries both for MyISAM and Innodb tables mysteriously stalling for few seconds with “NULL” in State column. These could be troubleshooted to waiting on Query Cache which at the same time had […]
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In this blog post, we’ll look at how using thread_statistics can cause high memory usage. I was recently working on a high memory usage issue for one of our clients, and made some interesting discoveries: high memory usage with no bounds. It was really tricky to diagnose. Below, I am going to show you how to […]
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Percona announces the release of Percona Monitoring and Management 1.1.2 on April 3, 2017. For installation instructions, see the Deployment Guide. This release includes several new dashboards in Metrics Monitor, updated versions of software components used in PMM Server, and a number of small bug fixes.
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The MariaDB subquery cache feature added in MariaDB 5.3 is not widely known. Let’s see what it is and how it works. What is a subquery cache? The MariaDB subquery cache optimizes the execution of correlated subqueries. Correlated subqueries refer to a value from the parent query. For example:
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SELECT id FROM product WHERE price NOT IN (SELECT MAX(price) FROM product GROUP BY category); |
MariaDB only uses this optimization if […]
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This blog compares how PostgreSQL and MySQL handle millions of queries per second. Anastasia: Can open source databases cope with millions of queries per second? Many open source advocates would answer “yes.” However, assertions aren’t enough for well-grounded proof. That’s why in this blog post, we share the benchmark testing results from Alexander Korotkov (CEO of […]
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This blog post was motivated by an internal discussion about how to fully disable query cache in MySQL. According to the manual, we should be able to disable “Query Cache” on the fly by changing query_cache_type to 0, but as we will show this is not fully true. This blog will show you how to properly disable “query […]
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Percona announces the release of Percona Server 5.6.33-79.0 on October 18th, 2016. Download the latest version from the Percona web site or the Percona Software Repositories. Based on MySQL 5.6.33, including all the bug fixes in it, Percona Server 5.6.33-79.0 is the current GA release in the Percona Server 5.6 series. Percona Server is open-source and free – this […]
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This blog updates Stephane Combaudon’s blog on MySQL performance tuning, and covers MySQL 5.7 performance tuning immediately after installation. A few years ago, Stephane Combaudon wrote a blog post on Ten MySQL performance tuning settings after installation that covers the (now) older versions of MySQL: 5.1, 5.5 and 5.6. In this post, I will look […]
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This blog post will detail the results of Samsung storage in tpcc-mysql benchmark using Percona Server. I had an opportunity to test different Samsung storage devices under tpcc-mysql benchmark powered by Percona Server 5.7. You can find a summary with details here https://github.com/Percona-Lab-results/201607-tpcc-samsung-storage/blob/master/summary-tpcc-samsung.md I have in my possession: Samsung 850 Pro, 2TB: This is a SATA device and […]
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