The query cache probes are fired when executing any query. What mysql buffer cache hit rate should you target. This stepbystep guide shows you how to assess your mysql database. I pulled some variable values after running the query to see if query cache is working. How to optimize mysql performance using mysqltuner linode. Retiring support for the query cache mysql server blog. The arguments contain the original query text and the number of rows returned from the query cache for the query. Mysql has the key cache hit ratio and innodb buffer pool ratio, oracle has the buffer cache hit ratio, and sybase and sql server use the data cache hit rate. This advisor does not evaluate against mysql 8, or higher. A look at the strategies, means and tools involved in viewing and monitoring your mysql query cache hit rate.
All of this without setting mysql s query cache size too large. What cache hit rate is good for optimal mysql performance is typical question im asked. What is its effect in my database and how it affects the performance. Despite query cache enabled it is not caching queries and it is telling index usage is 0.
I claim that somewhere around of 99% of advice about tuning mysql s key cache hit ratio is wrong, even when you hear it from experts. Here is the info for my server giga dedicated 6core. Mysql query cache for performance, avoid this when tuning. A mysql query cache size of 200 megabytes may even be too large. The key is to start very small maybe 10mb, then increase in small increments while trying to keep a high ratio of query cache hits and also a low. If you wish to follow along, youll need to download this tool, or something. To check whether the query cache is present in your mysql server, use the following statement. I have turned on query cache and have specified key buffer size based on the. There are two major problems with the key buffer hit ratio, and. Generally, you can increase the buffer cache hit ratio by increasing the amount of memory available to sql server. The key is to start very small maybe 10mb, then increase in small increments while trying to keep a high ratio of query cache hits and also a low amount of query cache low memory prunes. Mysqltuner is a highperformance mysql tuning perl script that gives a snapshot of the. Arunjith aravindan provides an overview of the mysql query cache.
I want to compute buffer cache hit ratio and group by instances. The query cache hit query is triggered when a query exists in the query cache and can be used to return the query cache information. I have not caused a fist fight in a while, so its time to take off the gloves. Bug reports, feature requests, and downloads at run with. The net result in our testing is that most common applications can get at least a 70% cache hit rate, and often higher. In both cases trying to come up with constant good hit rate is looking for trouble.