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From:Eric Bergen Date:May 29 2009 9:59pm
Subject:Re: Why can't I kill the query cache?
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You can also flush the cache with echo 1 > /proc/sys/vm/drop_caches if
you have a new enough kernel.

On Fri, May 29, 2009 at 2:16 PM, Dan Nelson <dnelson@stripped> wrote:
> In the last episode (May 29), Gerald L. Clark said:
>> Little, Timothy wrote:
>> > Also titled, I want this to run slow ALL the time...
>> >
>> > I have a group of dreadful queries that I have to optimize.
>> >
>> > Some take 20-30 seconds each -- the first time that I run them.  But
>> > then they never seem to take that long after the first time (taking less
>> > than a second then).  If I change the "keywords" searched for in the
>> > where clauses, then they take a long time again...  so it's the
>> > query-cache or something just like it.
>> >
>> > BUT, I am doing this each time :
>> > flush tables;
>> > reset query cache;
>> > set global query_cache_size=0;
>> > SELECT   SQL_NO_CACHE DISTINCT ca.conceptid AS headingid,
>> >
>> > And still it's not avoiding the cache.
>> >
>> > Is there a cache I'm missing?
>> >
>> > Tim...
>> >
>> >
>> Disk cache, but I don't know how to clear it.
>
> Create a file 2x the size of your RAM (for a 2gb system, dd if=/dev/zero
> of=bigfile bs=1024k count=4096), then dd it to /dev/null (dd if=bigfile
> of=/dev/null bs=1024k).  That should flush your OS cache.  The guaranteed
> way would be to dismount then remount your filesystem, but that could be
> difficult depending on how many other processes are using it..
>
> --
>        Dan Nelson
>        dnelson@stripped
>
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>



-- 
Eric Bergen
eric.bergen@stripped
http://www.ebergen.net
Thread
contributing to mysql ..mugisha moses27 May
  • Re: contributing to mysql ..Mattia Merzi27 May
    • RE: contributing to mysql ..Martin Gainty27 May
    • Why can't I kill the query cache?Timothy Little29 May
      • Re: Why can't I kill the query cache?Gerald L. Clark29 May
        • Re: Why can't I kill the query cache?Dan Nelson29 May
          • Re: Why can't I kill the query cache?Eric Bergen29 May
            • Re: Why can't I kill the query cache?Baron Schwartz30 May