From: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
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To: | Willy-Bas Loos <willybas(at)gmail(dot)com> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: turn off caching for performance test |
Date: | 2010-08-27 17:57:54 |
Message-ID: | AANLkTin7OCNMxnZeejraQ+vawy5rO0ZOZFC6WKzX00oR@mail.gmail.com |
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Thread: | |
Lists: | pgsql-performance |
On Thu, Aug 26, 2010 at 4:32 AM, Willy-Bas Loos <willybas(at)gmail(dot)com> wrote:
> Hi,
>
> I have a colleague that is convinced that the website is faster if
> enable_seqscan is turned OFF.
> I'm convinced of the opposite (better to leave it ON), but i would like to
> show it, prove it to him.
Stop, you're both doing it wrong. The issue isn't whether or not
turning off seq scans will make a few things faster here and there,
it's why is the query planner choosing sequential scans when it should
be choosing index scans.
So, what are your non-default settings in postgresql.conf?
Have you increased effective_cache_size yet?
Lowered random_page_cost?
Raised default stats target and re-analyzed?
Have you been looking at the problem queries with explain analyze?
What does it have to say about the planners choices?
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