Date: Thu, 4 Jun 2020 19:46:00 -0400
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Andres Freund <andres@anarazel.de>
Cc: Michael Paquier <michael@paquier.xyz>,
	Fujii Masao <masao.fujii@oss.nttdata.com>,
	Masahiko Sawada <masahiko.sawada@2ndquadrant.com>,
	Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
	sitnikov.vladimir@gmail.com,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: SIGSEGV from START_REPLICATION 0/XXXXXXX in XLogSendPhysical ()
 at walsender.c:2762
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On 2020-Jun-04, Andres Freund wrote:

> postgres[52656][1]=# SELECT 1;
> ┌──────────┐
> │ ?column? │
> ├──────────┤
> │        1 │
> └──────────┘
> (1 row)
> 
> 
> I am very much not in love with the way that was implemented, but it's
> there, and it's used as far as I know (cf tablesync.c).

Ouch ... so they made IDENT in the replication grammar be a trigger to
enter the regular grammar.  Crazy.  No way to put those worms back in
the tin now, I guess.

It is still my opinion that we should prohibit a logical replication
connection from being used to do physical replication.  Horiguchi-san,
Sawada-san and Masao-san are all of the same opinion.  Dave Cramer (of
the JDBC team) is not opposed to the change -- he says they're just
using it because they didn't realize they should be doing differently.

Both Michael P. and you are saying we shouldn't break it because it
works today, but there isn't a real use-case for it.

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