Re: Re: Increasing work_mem and shared_buffers on Postgres 9.2 significantly slows down queries

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От Claudio Freire
Тема Re: Re: Increasing work_mem and shared_buffers on Postgres 9.2 significantly slows down queries
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Msg-id CAGTBQpbuF0JHdure3N=UKFRLf8WW_hnQOKqCPgOK4UZ1pY1zQg@mail.gmail.com
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Ответ на Re: Re: Increasing work_mem and shared_buffers on Postgres 9.2 significantly slows down queries  (Jeff Janes <jeff.janes@gmail.com>)
Ответы Re: Re: Increasing work_mem and shared_buffers on Postgres 9.2 significantly slows down queries  (Claudio Freire <klaussfreire@gmail.com>)
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On Mon, Nov 5, 2012 at 2:09 PM, Jeff Janes <jeff.janes@gmail.com> wrote:
>>> In my experience when doing sorts in isolation, having more work_mem
>>> is a bad thing, unless it enables you to remove a layer of
>>> tape-merging.  I always blamed it on the L1/L2 etc. levels of caching.
>>
>> Blame it on quicksort, which is quite cache-unfriendly.
>
> The observation applies to heap sort.

Well, heapsort is worse, but quicksort is also quite bad.

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