…MySQL will allocate a lot of memory for table cache, especially if you’re using large blobs. It is easy to check…TIME: NULL UPDATE_TIME: NULL 3 rows in set (0.00 sec) Innodb Memory Usage Finally it is often helpful to check how…
Post: How FLUSH TABLES WITH READ LOCK works with Innodb Tables
March 23, 2012 By 20 Comments
…of the time it may take to complete this statement. Lets look at what the problem is. As of MySQL…
Post: Joining many tables in MySQL - optimizer_search_depth
April 20, 2012 By 5 Comments
…to be executed during EXPLAIN phase yet making it unusable to check the optimizer performance. Solution for this problem was to…query execution time to…execution plan computation would be more important than backward compatibility. In MySQL 5.6 things are likely to get even better handling joins of…
Post: Flexviews - part 3 - improving query performance using materialized views
April 4, 2011 By 12 Comments
…of execution time) of the query on which the view is based. The SQL features used in the query…time it takes to build the MVs the first time. Both of these views build in about the same about of time: mysql…how you can combine both types of views together. The complete method examples show how to…
Post: How to Monitor MySQL with Percona's Nagios Plugins
February 22, 2012 By 8 Comments
…to include others as well. Here’s how you can use our new monitoring plugins to check for some of…checking that the server is alive and responds to a query. The pmp-check-mysql-status is also very flexible and can be used to…
Post: Distributed Set Processing with Shard-Query
May 14, 2011 By 27 Comments
…how to distribute the computation of aggregation queries over time. I realised that I could apply these same mathematical concepts to distributed queries…Query can provide query execution plans based on the relational algebra rewrites So, here is an example of such a plan for a simple query…
Post: How to convert MySQL's SHOW PROFILES into a real profile
February 20, 2012 By 10 Comments
…how much time MySQL spends in various phases of query execution…query consumed 0.18 seconds. Where did the time go? mysql> SHOW PROFILE FOR QUERY 1; +———————-+———-+ | Status | Duration | +———————-+———-+ | starting | 0.000032 | | checking…
Post: MySQL Query Cache
July 27, 2006 By 69 Comments
…of people being confused, thinking MySQL Query Cache is the same as Oracle Query Cache – meaning cache where execution plans are cached. MySQL Query…of the query – Query Cache does simple optimization to check if query can be cached. As I mentioned only SELECT queries…
Post: Should we give a MySQL Query Cache a second chance ?
April 10, 2011 By 63 Comments
…of queries cache for given table. Instead we could track versions for tables (increment each time table is updated) and check…query item ? Right now none of such information is available which makes it hard to understand how exactly MySQL Query…
Post: Troubleshooting MySQL Upgrade Performance Regressions
February 15, 2012 By Leave a Comment
…about MySQL upgrade – version change but in a lot of cases this will happen when settings are changed at the same time, …changing how query is written and provide the hints. Check Query Execution If query execution plan looks the same it is good to check whenever it seems to be executing same…
