Date: Sat, 11 Jul 2020 17:26:30 -0400
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgbf@twiska.com, Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
	masao.fujii@oss.nttdata.com, pgsql-hackers@lists.postgresql.org
Subject: Re: min_safe_lsn column in pg_replication_slots view
Message-ID: <20200711212630.GA6825@alvherre.pgsql>
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On 2020-Jul-11, Tom Lane wrote:

> Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> > On 2020-Jul-09, Alvaro Herrera wrote:
> >> I think we should define InvalidXLogSegNo to be ~((uint64)0) and add a
> >> macro to test for that.
> 
> > That's overkill really.  I just used zero.  Running
> > contrib/test_decoding under valgrind, this now passes.
> 
> > I think I'd rather do away with the compare to zero, and initialize to
> > something else in GetWALAvailability, though.  What we're doing seems
> > unclean and unclear.
> 
> Is zero really not a valid segment number?

No, but you cannot retreat from that ...

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services