From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: Michael Paquier <michael@paquier.xyz>,
        Postgres hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: REINDEX INDEX results in a crash for an index of pg_class since
 9.6
In-reply-to: <20190502153107.o5zadep4ehebzoqy@alap3.anarazel.de>
References: <20190501013638.7u7fwr4zktbyyng5@alap3.anarazel.de>
 <25049.1556727622@sss.pgh.pa.us>
 <20190501170603.hx6r3ztyvi3rlgq6@alap3.anarazel.de>
 <20190501172115.4cvz3rp6np43odut@alap3.anarazel.de>
 <5483.1556737736@sss.pgh.pa.us> <16043.1556754084@sss.pgh.pa.us>
 <20190502012520.eyfhhn5ix2ooflys@alap3.anarazel.de>
 <27459.1556762513@sss.pgh.pa.us>
 <20190502021913.axyvyyyw5547swy5@alap3.anarazel.de>
 <25661.1556808540@sss.pgh.pa.us>
 <20190502153107.o5zadep4ehebzoqy@alap3.anarazel.de>
Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Thu, 02 May 2019 08:31:07 -0700"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <4869.1556811688.1@sss.pgh.pa.us>
Date: Thu, 02 May 2019 11:41:28 -0400
Message-ID: <4870.1556811688@sss.pgh.pa.us>
Precedence: bulk

Andres Freund <andres@anarazel.de> writes:
> ISTM that if we go down this path, we should split (not now, but either
> still in v12, or *early* in v13), the sets of indexes that are intended
> to a) not being used for catalog queries b) may be skipped for index
> insertions. It seems pretty likely that somebody will otherwise soon
> introduce an heap_update() somewhere into the index build process, and
> it'll work just fine in testing due to HOT.

Given the assertions you added in CatalogIndexInsert, I'm not sure
why that's a big hazard?

> I kinda wonder if there's not a third approach hiding somewhere here. We
> could just stop updating pg_class in RelationSetNewRelfilenode() in
> pg_class, when it's an index on pg_class.

Hmm ... are all those indexes mapped?  I guess so.  But don't we need
to worry about resetting relfrozenxid?

			regards, tom lane