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From:Michael Widenius Date:May 11 1999 2:00pm
Subject:MySQL slows down with "IN ( big-list )"
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>>>>> "Ken" == Ken Carroll <kenc@stripped> writes:

Ken> Hi.
Ken> 	I have noticed that MySQL slows down considerably when using a
Ken> statement
Ken> as follows:
Ken> 	SELECT *
Ken> 	FROM T
Ken> 	WHERE T.x IN ( 1, 2, 3, 4, 5, 6 ....., 120)
Ken> Are these values stored as a list or as a hash?  If they are a
Ken> hash, is there some value I can change so that the default hash
Ken> size is increased?   If it's a list, I guess I'm stuffed. :-(


MySQL uses a binary tree if all entries in the IN list are constants.

Did you try to use EXPLAIN on the above query?  Is T.x really indexed?

MySQL slows down with "IN ( big-list )"Ken Carroll10 May
  • MySQL slows down with "IN ( big-list )"Michael Widenius11 May
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