From: Tom Lane <tgl@sss.pgh.pa.us>
To: Masahiko Sawada <sawada.mshk@gmail.com>
cc: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>,
        "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: Reviewing freeze map code
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Comments: In-reply-to Masahiko Sawada <sawada.mshk@gmail.com>
	message dated "Mon, 06 Jun 2016 17:44:09 +0900"
Date: Mon, 06 Jun 2016 09:53:08 -0400
Message-ID: <5402.1465221188@sss.pgh.pa.us>
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Masahiko Sawada <sawada.mshk@gmail.com> writes:
> On Sat, Jun 4, 2016 at 1:46 PM, Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>> So other idea is to have GUC parameter, vacuum_even_frozen_page for example.
>> If this parameter is set true (false by default), we do vacuum whole
>> table forcibly and re-generate visibility map.
>> The advantage of this idea is that we don't necessary to expand VACUUM
>> syntax and relatively easily can remove this parameter if it's not
>> necessary anymore.

> Attached is a sample patch that controls full page vacuum by new GUC parameter.

I find this approach fairly ugly ... it's randomly inconsistent with other
VACUUM parameters for no very defensible reason.  Taking out GUCs is not
easier than taking out statement parameters; you risk breaking
applications either way.

			regards, tom lane


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