Search Results for: mysql table cache hits

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 […]

MySQL Query Cache

MySQL has a great feature called “Query Cache” which is quite helpful for MySQL Performance optimization tasks but there are number of things you need to know. First let me clarify what MySQL Query Cache is – I’ve seen number of people being confused, thinking MySQL Query Cache is the same as Oracle Query Cache […]

What MySQL buffer cache hit rate should you target

“What cache hit rate is good for optimal MySQL Performance” is typical question I’m asked. It could by MyISAM key_buffer or Innodb innodb_buffer_pool it does not really matter. In both cases trying to come up with constant “good” hit rate is looking for trouble. Well of course you can name 100% hit rate and all […]

Testing backup locks during Xtrabackup SST on Percona XtraDB Cluster

Background on Backup Locks I was very excited to see Backup locks support in release notes for the latest Percona XtraDB Cluster 5.6.21 release. For those who are not aware, backup locks offer an alternative to FLUSH TABLES WITH READ LOCK (FTWRL) in Xtrabackup. While Xtrabackup can hot-copy Innodb, everything else in MySQL must be locked (usually […]

Percona Server 5.1.53-12.4

Percona Server version 5.1.53-12.4 is now available for download. It is now the current stable release version. Functionality Added or Changed  Percona Server 5.1.53-12.4 is based on MySQL 5.1.53.  New Features Added: Precompiled UDFs for Maatkit (FNV and MurmurHash hash functions to provide faster checksums) are now included in distributions. Fixes feature request #689992. (Aleksandr Kuzminsky) […]

Percona Server 5.1.52-rel11.6

Percona Server version 5.1.52-rel11.6 is now available for download. The main purpose of this release is to update the current Percona stable release to the latest version of MySQL 5.1. Functionality Added or Changed  Percona Server 5.1.52-rel11.6 is now based on MySQL 5.1.52.  New Features Added: None  Other Changes: None Bugs Fixed Bug #671764 – […]

How innodb_open_files affects performance

Recently I looked at table_cache sizing which showed larger table cache does not always provides the best performance. So I decided to look at yet another similar variable – innodb_open_files which defines how many files Innodb will keep open while working in innodb_file_per_table mode. Unlike MyISAM Innodb does not have to keep open file descriptor […]