…indexes on them, MySQL could sometimes make use of the multiple indexes. For instance, “SELECT foo FROM bar WHERE indexed_colA = X OR indexed… 3.2806 0.50 0.02 SELECT user Note the low V/M here. This query *… (it did), but it might also negatively impact other queries which were benefitting from this …
Post: MySQL caching methods and tips
April 4, 2011 By 5 Comments
…impacted. The invalidation frequency is controlled by the rate of…of the unpredictable performance of the MySQL query cache, since the rate of… is low, …indexed appropriately for your queries. Using INSERT .. SELECT for summary tables The INSERT .. SELECT approach works best when there is some sort of…
Post: MySQL Partitioning - can save you or kill you
December 11, 2010 By 45 Comments
…impact on master too. Master in its turn was getting a lot of lookups by the uu value which is not part of…of partitions made replication less efficient but the number of selects…
Comment: How to find wrong indexing with glance view
August 23, 2008 By 27 Comments
…selective than any of its columns alone. If you don’t have such compound index then mysql most probably use index…mysql can use index to filter records before fetching any rows. How much it will give? Not many, worth investigation. May be impact…
Post: Knowing what pt-online-schema-change will do
November 1, 2012 By 1 Comment
…LOW_PRIORITY IGNORE INTO `test`.`_t_new` (`id`, `guest_language`, `guest_country`, `score`) SELECT…should not impact the …SELECT `id`, `guest_language`, `guest_country`, `score` FROM `test`.`t` FORCE INDEX…of the table’s structure, available indexes, total number of…with the MySQL server (privileges,…
