Re: Visibility map and hint bits

From: Merlin Moncure <mmoncure(at)gmail(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Visibility map and hint bits
Date: 2011-05-05 18:11:41
Message-ID: BANLkTi=o_PaeL28OKiODfAg6EMFMvbabcA@mail.gmail.com
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On Thu, May 5, 2011 at 11:59 AM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> There has been a lot of recent discussion about the visibility map (for
> index-only scans) and hint bits (trying to avoid double-writing a
> table).

I still think a small tqual.c maintained cache of hint bits will
effectively eliminate hint bit i/o issues surrounding bulk loads. Tom
fired a shot across the bow regarding the general worthiness of that
technique though (see:
http://postgresql.1045698.n5.nabble.com/Process-local-hint-bit-cache-td4270229.html)
:(. I can rig up a cleaned up version of the patch pretty
easily...it's a local change and fairly simple.

I don't think there is any way to remove the hint bits without
suffering some other problem.

merlin

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