…row *************************** id: 1 select_type: SIMPLE table: employees type: index possible_keys: NULL key: idx_first key_len: 16 ref: NULL rows: 300584 Extra: Using index…
Post: Advanced index analysis with mk-index-usage
November 11, 2010 By 2 Comments
…use different indexes, and what fraction of the time is each index chosen? SELECT…how to read this — the first row says that query 1262633894049058504 has two variations. One variation uses the mpb_wordpress.wp_posts.post_status index…
Post: Using Multiple Key Caches for MyISAM Scalability
November 26, 2008 By 8 Comments
…to use Multiple Key Caches the question is how many to use, what sizes to allocate and how to map tables to them. One simple solution I use…
Post: Using UNION to implement loose index scan in MySQL
August 10, 2006 By 15 Comments
…Using Index” in EXPLAIN output or it will read row data for all rows – it can’t read Index and perform row…selective enough by itself. For example if we would like to only lookup people within single zip I would advice to use index…
Post: How (not) to find unused indexes
October 16, 2009 By 2 Comments
…a pretty good index! It’s not always like this, but there are a lot of cases where applications have good selectivity…index can not filter out enough rows to be effective. I see this a lot in consulting issues where customers have queries that use a…
Post: ORDER BY ... LIMIT Performance Optimization
September 1, 2006 By 100 Comments
…rows generated. For example if I do SELECT * FROM sites ORDER BY date_created DESC LIMIT 10; I would use index on (date_created) to…to watch for, if you do not have full where clause resolved by index is how many rows you need to scan to…
Comment: Database problems in MySQL/PHP Applications
August 11, 2006 By 13 Comments
…how to create indexes. Foreign key references may add processing time to…rows are scanned and returned. SELECT * FROM articles INNER JOIN users ON users.id = articles.user_id AND users.featured = 1 ; > Use Indexes…
Post: MySQL 5.6.10 Optimizer Limitations: Index Condition Pushdown
March 14, 2013 By 2 Comments
…How…rows: 10259274 Extra: Using where; Using index 1 row in set (0.00 sec) I reported this issue to…Using index” -in most cases it will be the right solution because our SELECT will only be faster when the condition is very selective…
Post: The Optimization That (Often) Isn't: Index Merge Intersection
December 14, 2012 By 6 Comments
…rows: 8100 Extra: Using intersect(user_type,status,parent_id); Using where; Using index; Using…index_merge_intersection, it’s a good time to make sure that the indexes involved have good selectivity (a good practice in general, to…
Post: Percona XtraDB Cluster: Failure Scenarios with only 2 nodes
July 25, 2012 By 6 Comments
…index defers as expected. Now let’s stop the communication between both nodes (using firewall rules): iptables -A…to select a Primary Component, we have then a split-brain condition. In our 2 nodes setup when a node loses connection to…row affected (0.02 sec) percona2 mysql> select…
