MySQL Forums
Forum List  »  Performance

Re: Queries slow down daily, optimizing helps -> why?
Posted by: Rick James
Date: February 27, 2009 07:56PM

More details may be in the slowlog.

Your earlier attempts probably said 24K "Rows examined". This was a full scan of one table, plus probing the other table for every row in the first one.

With the new index, "Rows examined" is probably about 13K -- full scan of one table, filtering out most of the rows, then probing the other table only for the remaining rows.

I would not make a general rule on which table should be "on top" in Explain. There are a zillion things that Explain might say; I enjoy explaining one EXPLAIN at a time. You may find a dozen such postings in this forum, plus Newbie and Optimizer forums.

Options: ReplyQuote

Written By
March 18, 2009 03:58AM
Re: Queries slow down daily, optimizing helps -> why?
February 27, 2009 07:56PM

Sorry, you can't reply to this topic. It has been closed.

Content reproduced on this site is the property of the respective copyright holders. It is not reviewed in advance by Oracle and does not necessarily represent the opinion of Oracle or any other party.