… fix of my favorite bug 15815. I wrote about this problem before and also investigated in my presentation. Finally bug fix… (without bugfix): select sql_calc_found_rows * from b limit 5; executes for 20 sec (table b contains ~2 mil rows) the same query but…
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
… thousands of OS waits per second it may be the problem. The other way to look at it is context switch… id 8079, query id 728899 localhost root Sending data select sql_calc_found_rows * from b limit 5 Trx read view will not see… id 8078, query id 728898 localhost root Sending data select sql_calc_found_rows * from b limit 5 Trx read view will not see…
Post: Are you designing IO bound or CPU bound application ?
December 20, 2006 By 10 Comments
… high) I would highlight this query as possibly having performance problems. Also do not look just at “typical” case – in many cases worst 5% would be responsible for majority of performance problems. Let me illustrate it on simple case. Assuming you have… select count(*) from messages where user_id=134 or use SQL_CALC_FOUND_ROWS flag for your main select query. If you’re having…
Comment: Backport of micro-time patch to mysql 4.1
October 9, 2006 By 9 Comments
Michael, Good you’ve found the problem. Regarding query you have in your example it is slow because of SQL_CALC_FOUND_ROWS – it effectively negates the limit.
Comment: JOIN Performance & Charsets
April 3, 2010 By 2 Comments
… one problem with join. I need to reduce query time to it optimized level. Details are as under QUERY: SELECT SQL_CALC_FOUND_ROWS p…
