Re: [COMMITTERS] pgsql: Reset btpo.xact following recovery of btree delete page.

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: [COMMITTERS] pgsql: Reset btpo.xact following recovery of btree delete page.
Date: 2010-03-19 15:32:29
Message-ID: 1269012749.3556.278.camel@ebony
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On Fri, 2010-03-19 at 08:41 -0400, Tom Lane wrote:
> sriggs(at)postgresql(dot)org (Simon Riggs) writes:
> > Log Message:
> > -----------
> > Reset btpo.xact following recovery of btree delete page. Add btpo_xact
> > field into WAL record and reset it from there, rather than using
> > FrozenTransactionId which can lead to some corner case bugs.
>
> Simon, you can't just whack WAL record contents around without a care.
> This commit breaks on-disk WAL compatibility and will result in possibly
> unrecoverable databases as soon as someone applies it; not to mention
> what will happen if an HS slave is not running the same code as its
> master. This must be treated as an initdb-forcing, or at least
> pg_resetxlog-forcing, change.

OK, understood.

> The correct thing to do when committing such a change is to change the
> WAL-file magic number XLOG_PAGE_MAGIC.

Will do

--
Simon Riggs www.2ndQuadrant.com

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