Re: GiST, caching, and consistency

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Matthew Wakeling <matthew(at)flymine(dot)org>
Cc: Greg Stark <gsstark(at)mit(dot)edu>, pgsql-performance(at)postgresql(dot)org
Subject: Re: GiST, caching, and consistency
Date: 2009-08-05 13:42:54
Message-ID: 603c8f070908050642x4ac57a9ev2e9c64a2352c10b3@mail.gmail.com
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On Wed, Aug 5, 2009 at 6:20 AM, Matthew Wakeling<matthew(at)flymine(dot)org> wrote:
> It is certainly doing a sequential scan. So are you saying that it will
> start a sequential scan from a different part of the table each time, even
> in the absence of other simultaneous sequential scans? Looks like I'm going
> to have to remove the limit to get sensible results - I only added that to
> make the query return in a sensible time for performance testing.
>
> Some trivial testing with "select * from location limit 10;" indicates that
> it starts the sequential scan in the same place each time - but is this
> different from the above query?

Maybe it's because of this?

http://www.postgresql.org/docs/8.3/static/runtime-config-compatible.html#GUC-SYNCHRONIZE-SEQSCANS

...Robert

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