ALTER TABLE on system catalogs

From: Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)anarazel(dot)de>
Cc: Michael Paquier <michael(at)paquier(dot)xyz>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: ALTER TABLE on system catalogs
Date: 2018-08-21 15:04:41
Message-ID: a33f9d7f-4afe-a351-3528-cc32b0603845@2ndquadrant.com
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On 20/08/2018 15:34, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
>> On 2018-08-20 14:38:25 +0200, Peter Eisentraut wrote:
>>> Do you have an alternative in mind?
>
>> One is to just not do anything. I'm not sure I'm on board with the goal
>> of changing things to make DDL on system tables more palatable.
>
> FWIW, I agree with doing as little as possible here. I'd be on board
> with Andres' suggestion of just swapping the two code stanzas so that
> the no-op case doesn't error out. As soon as you go beyond that, you
> are in wildly unsafe and untested territory.

That doesn't solve the original problem, which is being able to set
reloptions on pg_attribute, because pg_attribute doesn't have a toast
table but would need one according to existing rules.

Attached is a patch that instead moves those special cases into
needs_toast_table(), which was one of the options suggested by Andres.
There were already similar checks there, so I guess this makes a bit of
sense.

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Attachment Content-Type Size
v2-0001-Ignore-attempts-to-add-TOAST-table-to-shared-or-c.patch text/plain 4.0 KB

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