Subject: Re: Visibility map, partial vacuums
From: Simon Riggs <simon@2ndQuadrant.com>
To: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
In-Reply-To: <4905AE17.7090305@enterprisedb.com>
References: <4905AE17.7090305@enterprisedb.com>
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Date: Tue, 28 Oct 2008 11:25:08 +0000
Message-Id: <1225193108.3971.154.camel@ebony.2ndQuadrant>
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On Mon, 2008-10-27 at 14:03 +0200, Heikki Linnakangas wrote:
> One option would be to just ignore that problem for now, and not 
> WAL-log.

Probably worth skipping for now, since it will cause patch conflicts if
you do. Are there any other interactions with Hot Standby? 

But it seems like we can sneak in an extra flag on a HEAP2_CLEAN record
to say "page is now all visible", without too much work.

Does the PD_ALL_VISIBLE flag need to be set at the same time as updating
the VM? Surely heapgetpage() could do a ConditionalLockBuffer exclusive
to set the block flag (unlogged), but just not update VM. Separating the
two concepts should allow the visibility check speed gain to more
generally available. 

-- 
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support