…to the secondary index definition can result in a lot of Random I/O. The purpose of MRR is to reduce…query runs the optimizer would switch to using plan ‘a’, which does not involve MRR, and the query time for MySQL…
Post: Troubleshooting MySQL Memory Usage
March 21, 2012 By 3 Comments
…to guess and test, you can’t get information of how much memory connection uses and for which purposes it is allocated. Reducing…In Percona Server you can do better as you can query temporary tables too: mysql…in MySQL. Most suspected memory leaks end up being some run…
Post: Modeling MySQL Capacity by Measuring Resource Consumptions
March 8, 2011 By 1 Comment
…How to get CPU consumption per query ? You can take a look at procfs for MySQL process: root@ubuntu:/var/log/mysql…to number of queries running will give average CPU usage per query. If you’re running…to reduce wait time and number of IOs per query as well as increase CPU time…
Post: How To Test Your Upgrades - pt-upgrade
December 29, 2011 By 1 Comment
…query-digest like the commands below # to limit the number of queries per fingerprint to test with. pt-upgrade –fingerprints –run-time…in general how each fingerprint performs on the test servers. About 10% variation is tolerable and can be accounted for other MySQL…
Post: Aligning IO on a hard disk RAID – the Benchmarks
June 9, 2011 By 11 Comments
…to IO alignment yourself. In this case offset is correct, but file system is unaware how to…to high concurrency response time in the first case is significantly better. It would be interesting however to run…
Post: Is your server's performance about to degrade?
May 18, 2010 By 13 Comments
…Reducing the load by half through the load balancer did not restore proper response time…queries at 0-second threshold (all queries) and crunched it with mk-query-digest. Side note: bravo for Daniel figuring out how to make mk-query…to the MySQL source code are necessary. But in…
Post: Distributed Set Processing with Shard-Query
May 14, 2011 By 27 Comments
… operations on reduced sets. Keep in mind, …how to distribute the computation of aggregation queries over time. I realised that I could apply these same mathematical concepts to distributed queries…-by reduction is run over the coordination…MySQL storage nodes are supported. Amdahl’s law applies to…
Post: Reasons for MySQL Replication Lag
July 29, 2011 By 6 Comments
…reduced performance causing replication to lag. Failed hard drive getting RAID in…MySQL Restart MySQL Restarts may include recovery time…In could be even system which queries mysql. I’ve seen monitoring updates which would add excessively expensive and frequent query…
Post: MySQL EXPLAIN limits and errors.
July 24, 2006 By 6 Comments
…to rebuild index by sort of key_cache as it can for MyISAM. EXPLAIN may take long time In MySQL…in select in from clause EXPLAIN might never complete. Solution is to run EXPLAIN for statements in FROM clause separately before looking at main query…reduces number of passes MySQL had to…
Post: MySQL Query Cache
July 27, 2006 By 69 Comments
…to be cached. Query must be deterministic – Query might provide same result no matter how many times it is run…reduce query_cache appropriately. Otherwise you might wish to…to use query cache ? Third party application – You can’t change how it works with MySQL to add caching but you can enable query…
