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From:Michael Widenius Date:September 29 1999 12:42pm
Subject:Re: temp tables in memory vs. disk
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>>>>> "Rick" == Rick Moore <lrmoore@stripped> writes:

Rick> I'm seeing the same thing with 3.23.3, but the real odd thing is that CPU
Rick> and disk activity are extremely low.  I can't figure out what's taking so
Rick> long...

Rick> Rick

If you could post the query in question, I may be able to comment on this..

Rick> ----- Original Message -----
Rick> From: David Sklar <sklar@stripped>
Rick> To: <mysql@stripped>
Rick> Sent: Monday, September 27, 1999 1:26 PM
Rick> Subject: temp tables in memory vs. disk


>> How can I find out if, for a particular query, MySQL uses tmp tables in
Rick> memory
>> or on disk? I get a bunch of queries that sit in 'Copying to tmp table'
Rick> state
>> for too long (but they do finish), and I want to see if I can tune some
Rick> params
>> to speed them up. I am using 3.22.14-gamma.

You can 'easily' check this if you have any temporary files named
SQL-* in /tmp or /var/tmp while you do the query.

MySQL will use in memory tables if the result of the SELECT doesn't
contain BLOB/TEXT columns and you are not using SQL_BIG_TABLES.

Generally, MySQL 3.23 is much faster on GROUP BY and DISTINCT queries
than 3.22.

Regards,
Monty
Thread
temp tables in memory vs. disk(David Sklar)27 Sep
  • Re: temp tables in memory vs. diskRick Moore27 Sep
    • Re: temp tables in memory vs. diskMichael Widenius29 Sep
  • Re: temp tables in memory vs. diskCooper Vertz12 Oct
    • Re: temp tables in memory vs. diskMichael Widenius13 Oct
  • Re: temp tables in memory vs. diskCooper Vertz13 Oct
  • Re: temp tables in memory vs. diskCooper Vertz16 Oct
    • Re: temp tables in memory vs. disksinisa16 Oct