Received: from malur.postgresql.org ([217.196.149.56])
	by arkaria.postgresql.org with esmtps
 (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256)
	(Exim 4.92)
	(envelope-from <pgsql-hackers-owner+archive@lists.postgresql.org>)
	id 1kEcll-0005mU-SZ
	for pgsql-hackers@arkaria.postgresql.org; Sat, 05 Sep 2020 18:18:33 +0000
Received: from localhost ([127.0.0.1] helo=malur.postgresql.org)
	by malur.postgresql.org with esmtp (Exim 4.92)
	(envelope-from <pgsql-hackers-owner+archive@lists.postgresql.org>)
	id 1kEclk-0005WU-Qt
	for pgsql-hackers@arkaria.postgresql.org; Sat, 05 Sep 2020 18:18:32 +0000
Received: from makus.postgresql.org ([2001:4800:3e1:1::229])
	by malur.postgresql.org with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256)
	(Exim 4.92)
	(envelope-from <tgl@sss.pgh.pa.us>)
	id 1kEclk-0005WN-EA
	for pgsql-hackers@lists.postgresql.org; Sat, 05 Sep 2020 18:18:32 +0000
Received: from sss.pgh.pa.us ([66.207.139.130])
	by makus.postgresql.org with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256)
	(Exim 4.92)
	(envelope-from <tgl@sss.pgh.pa.us>)
	id 1kEcli-0001Xb-AB
	for pgsql-hackers@lists.postgresql.org; Sat, 05 Sep 2020 18:18:31 +0000
Received: from sss1.sss.pgh.pa.us (localhost [127.0.0.1])
	by sss.pgh.pa.us (8.15.2/8.15.2) with ESMTP id 085IITQo1222283
	for <pgsql-hackers@lists.postgresql.org>; Sat, 5 Sep 2020 14:18:29 -0400
From: Tom Lane <tgl@sss.pgh.pa.us>
To: pgsql-hackers@lists.postgresql.org
Subject: Re: Dubious code in pg_rewind's process_target_file()
In-reply-to: <1221796.1599329320@sss.pgh.pa.us>
References: <1221796.1599329320@sss.pgh.pa.us>
Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Sat, 05 Sep 2020 14:08:40 -0400"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <1222281.1599329909.1@sss.pgh.pa.us>
Date: Sat, 05 Sep 2020 14:18:29 -0400
Message-ID: <1222282.1599329909@sss.pgh.pa.us>
List-Id: <pgsql-hackers.lists.postgresql.org>
List-Help: <https://lists.postgresql.org/manage/>
List-Subscribe: <https://lists.postgresql.org/manage/>
List-Post: <mailto:pgsql-hackers@lists.postgresql.org>
List-Owner: <mailto:pgsql-hackers-owner@lists.postgresql.org>
List-Archive: <https://www.postgresql.org/list/pgsql-hackers>
Precedence: bulk

I wrote:
> It looks to me like we could replace "exists = false" with "return",
> rather than uselessly constructing a FILE_ACTION_REMOVE entry for
> a file we've already proven is not there.

Or actually, maybe we should just drop the lstat call altogether?
AFAICS it's 99.99% redundant with the lstat that traverse_datadir
has done nanoseconds before.  Yeah, maybe somebody managed to drop
the file in between, but the FILE_ACTION_REMOVE code would have to
deal with such cases anyway in case a drop occurs later.

			regards, tom lane