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To: Geoff Tolley <geoff.tolley@yougov.com>
cc: pgsql-admin@postgresql.org
Subject: Re: Alter column varchar(n) via updating pg_attribute 
In-reply-to: <4E600A2C.9030307@yougov.com> 
References: <4E600A2C.9030307@yougov.com>
Comments: In-reply-to Geoff Tolley <geoff.tolley@yougov.com>
	message dated "Thu, 01 Sep 2011 17:41:48 -0500"
Date: Fri, 02 Sep 2011 00:34:04 -0400
Message-ID: <4444.1314938044@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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Geoff Tolley <geoff.tolley@yougov.com> writes:
> The last time this was asked about 
> (http://archives.postgresql.org/pgsql-admin/2010-02/msg00189.php), 9.0 
> was still alpha.

> Is there any reason to suspect that direct pg_attribute manipulation to 
> expand a varchar(n) column might not play nice with streaming 
> replication/hot standby?  (Naturally I'm also in the process of testing).

I can't see why it wouldn't.  The WAL/replication mechanism works at
such a low level that it has no idea whether an update to pg_attribute
originated in an official DDL command or a manual UPDATE of the catalog.
I think you should be more worried about fat-fingering the update than
whether it will be replicated correctly.

But, of course, testing is always a good idea ;-)

			regards, tom lane