Date: Wed, 25 Aug 2021 20:20:04 -0400
From: "alvherre@alvh.no-ip.org" <alvherre@alvh.no-ip.org>
To: Jakub Wartak <Jakub.Wartak@tomtom.com>
Cc: "Bossart, Nathan" <bossartn@amazon.com>,
	Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
	"pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>,
	"mengjuan.cmj@alibaba-inc.com" <mengjuan.cmj@alibaba-inc.com>
Subject: Re: prevent immature WAL streaming
Message-ID: <202108260020.cjxmmc2m7iws@alvherre.pgsql>
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BTW while going about testing this, I noticed that we forbid
pg_walfile_name() while in recovery.  That restriction was added by
commit 370f770c15a4 because ThisTimeLineID was not set correctly during
recovery.  That was supposed to be fixed by commit 1148e22a82ed, so I
thought that it should be possible to remove the restriction.  However,
I did that per the attached patch, but was quickly disappointed because
ThisTimeLineID seems to remain zero in a standby for reasons that I
didn't investigate.

-- 
Álvaro Herrera           39°49'30"S 73°17'W  —  https://www.EnterpriseDB.com/
"The problem with the facetime model is not just that it's demoralizing, but
that the people pretending to work interrupt the ones actually working."
                                                           (Paul Graham)

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	filename="0001-Don-t-forbid-pg_walfile_name-in-recovery-mode.patch"

From 1b57e504b9a7eeddf2d99e615f21c5aec042a908 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Wed, 25 Aug 2021 19:55:43 -0400
Subject: [PATCH] Don't forbid pg_walfile_name in recovery mode

---
 src/backend/access/transam/xlogfuncs.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index b98deb72ec..99b22d0b30 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -503,13 +503,6 @@ pg_walfile_name(PG_FUNCTION_ARGS)
 	XLogRecPtr	locationpoint = PG_GETARG_LSN(0);
 	char		xlogfilename[MAXFNAMELEN];
 
-	if (RecoveryInProgress())
-		ereport(ERROR,
-				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
-				 errmsg("recovery is in progress"),
-				 errhint("%s cannot be executed during recovery.",
-						 "pg_walfile_name()")));
-
 	XLByteToPrevSeg(locationpoint, xlogsegno, wal_segment_size);
 	XLogFileName(xlogfilename, ThisTimeLineID, xlogsegno, wal_segment_size);
 
-- 
2.30.2


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