From: Tom Lane <tgl@sss.pgh.pa.us>
To: Fujii Masao <masao.fujii@gmail.com>
cc: Martijn van Oosterhout <kleptog@svana.org>,
 Andres Freund <andres@anarazel.de>,
 PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: WAL logging problem in 9.4.3?
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Comments: In-reply-to Fujii Masao <masao.fujii@gmail.com>
 message dated "Sat, 04 Jul 2015 01:39:42 +0900"
Date: Fri, 03 Jul 2015 12:53:56 -0400
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Fujii Masao <masao.fujii@gmail.com> writes:
> Okay, so probably we need to change WAL replay of TRUNCATE so that
> the index file is truncated to one containing only meta page instead of
> empty one. That is, the WAL replay of TRUNCATE would need to call
> index_build() after smgrtruncate() maybe.

That seems completely unworkable.  For one thing, index_build would expect
to be able to do catalog lookups, but we can't assume that the catalogs
are in a good state yet.

I think the responsibility has to be on the WAL-writing end to emit WAL
instructions that lead to a correct on-disk state.  Putting complex
behavior into the reading side is fundamentally misguided.

			regards, tom lane


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