Date: Fri, 17 Dec 2021 08:55:23 +0900
From: Michael Paquier <michael@paquier.xyz>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>,
	"wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>,
	"pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>,
	Andres Freund <andres@anarazel.de>
Subject: Re: Confused comment about drop replica identity index
Message-ID: <YbvR69c7Z7VDjXSg@paquier.xyz>
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On Thu, Dec 16, 2021 at 03:08:46PM -0300, Alvaro Herrera wrote:
> Hmm, so if a table has REPLICA IDENTITY INDEX and there is a publication
> with an explicit column list, then we need to forbid the DROP INDEX for
> that index.

Hmm.  I have not followed this thread very closely.

> I wonder why don't we just forbid DROP INDEX of an index that's been
> defined as replica identity.  It seems quite silly an operation to
> allow.

The commit logs talk about b23b0f55 here for this code, to ease the
handling of relcache entries for rd_replidindex.  07cacba is the
origin of the logic (see RelationGetIndexList).  Andres?

I don't think that this is really an argument against putting more
restrictions as anything that deals with an index drop, including the
internal ones related to constraints, would need to go through
index_drop(), and new features may want more restrictions in place as
you say.

Now, I don't see a strong argument in changing this behavior either
(aka I have not looked at what this implies for the new publication
types), and we still need to do something for the comment/docs in
existing branches, anyway.  So I would still fix this gap as a first
step, then deal with the rest on HEAD as necessary.
--
Michael

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