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Re: Subquery with range uses filesort
Posted by: David Marcus
Date: November 19, 2013 08:36PM

> But is the filesort really hurting performance?

I don't know. I could test it, with some effort. But, if the query
returns a few hundred or thousand players and MySQL has to sort a
dozen or a hundred records for each player, I would think the sorting
would take a noticeable amount of time.

> > select * from Player
> > `PlayerPassword` tinyblob NOT NULL,
> conspire to force the temp table to be on disk.

I'm not actually fetching that column.

The temp table is declared "engine=memory". I used to not specify the
engine for the temp table. When my hosting company upgraded MySQL,
queries started timing out. I figured out that the temp table had
switched from MyISAM to InnoDB. With InnoDB, updating one row of the
temp table took 0.1 second. With a memory table, 0.0001 seconds.

> Are you fetching info about _one_ player? Or several players?

People enter criteria on

http://www.ratingscentral.com/PlayerSearch.php

The results can contain anywhere from one player to 54,106.

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