From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
---|---|
To: | Andres Freund <andres(at)anarazel(dot)de> |
Cc: | Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Masahiko Sawada <masahiko(dot)sawada(at)2ndquadrant(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, sitnikov(dot)vladimir(at)gmail(dot)com, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: SIGSEGV from START_REPLICATION 0/XXXXXXX in XLogSendPhysical () at walsender.c:2762 |
Date: | 2020-06-03 22:27:12 |
Message-ID: | 20200603222712.GA11510@alvherre.pgsql |
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Lists: | pgsql-hackers |
On 2020-Jun-03, Andres Freund wrote:
> I don't think we should prohibit this. For one, it'd probably break some
> clients, without a meaningful need.
There *is* a need, namely to keep complexity down. This is quite
convoluted, it's got a lot of historical baggage because of the way it
was implemented, and it's very difficult to understand. The greatest
motive I see is to make this easier to understand, so that it is easier
to modify and improve in the future.
> But I think it's also actually quite useful to be able to access
> catalogs before streaming data. You e.g. can look up configuration of
> the primary before streaming WAL. With a second connection that's
> actually harder to do reliably in some cases, because you need to be
> sure that you actually reached the right server (consider a pooler,
> automatic failover etc).
I don't think having a physical replication connection access catalog
data directly is a great idea. We already have gadgets like
IDENTIFY_SYSTEM for physical replication that can do that, and if you
need particular settings you can use SHOW (commit d1ecd539477). If
there was a strong need for even more than that, we can add something to
the grammar.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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