… by Gokhan inspired me to write a bit about descending indexes and about loose index scan, or what Gokhan calls “better range” support… general – these are features MySQL should get for all storage engines at some point. Descending indexes – This is something MySQL does not have at… in your comments please also explain which indexes do you have on the table. SHOW CREATE TABLE is the best. Otherwise I…
Post: ORDER BY ... LIMIT Performance Optimization
September 1, 2006 By 100 Comments
… in the list now so index on (category_id, date_created) can’t be used directly. Index on date_created separately would still work… this would be to have index which is sorted appropriately (ascending by col1 and descending by col2) but MySQL can’t do it… long as it is indexed) Force index if needed In some cases MySQL Optimizer may prefer to use different index, which has better selectivity…
Post: Heikki Tuuri Innodb answers - Part I
October 26, 2007 By 19 Comments
…index scans more efficient. I can’t wait for ability to create physically sorted indexes with Innodb (with index… index page in the ascending order is. InnoDB has a similar heuristic for descending index scans… ha_innodb.cc in 5.1: static MYSQL_SYSVAR_ULONG(thread_concurrency, srv_thread_concurrency…
Comment: Descending indexing and loose index scan
June 20, 2006 By 6 Comments
…, because I have an index on (scraped,siteid), but as of MySQL 5.0.21 there is no descending index possible, so how would you suggest I manage the descending index? I noticed… use, which means maybe there is a better way then creating a ‘negative value’ column or something that I could sort…
