At Wed, 25 Aug 2021 20:20:04 -0400, "alvherre@alvh.no-ip.org" <alvherre@alvh.no-ip.org> wrote in
> 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.
On a intermediate node of a cascading replication set, timeline id on
walsender and walrecever can differ and ordinary backends cannot
decide which to use.
regards.
--
Kyotaro Horiguchi
NTT Open Source Software Center