Re: collateral benefits of a crash-safe visibility map

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: Merlin Moncure <mmoncure(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: collateral benefits of a crash-safe visibility map
Date: 2011-05-10 17:02:59
Message-ID: BANLkTi=1b3Cw_GREU1ROau39BO-3nWC7+w@mail.gmail.com
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On Tue, May 10, 2011 at 12:57 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> Hmmm, do we really need to WAL log freezing?
>
> Can we break down freezing into a 2 stage process, so that we can have
> first stage as a lossy operation and a second stage that is WAL
> logged?

That might solve the relfrozenxid problem - set the bits in the heap,
sync the heap, then update relfrozenxid once the heap is guaranteed
safely on disk - but it again seems problematic for Hot Standby.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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