Subject: Re: Converting contrib SQL functions to new style
To: Tom Lane <tgl@sss.pgh.pa.us>, Mark Dilger <mark.dilger@enterprisedb.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
 Peter Eisentraut <peter.eisentraut@enterprisedb.com>,
 Robert Haas <robertmhaas@gmail.com>
References: <3395418.1618352794@sss.pgh.pa.us>
 <C7AA1711-AE83-4DA3-9D7F-2188B15ABD50@enterprisedb.com>
 <3565758.1618421782@sss.pgh.pa.us>
From: Vik Fearing <vik@postgresfriends.org>
Message-ID: <564283e2-3ba5-54ac-1d6b-d86bef3d9dc9@postgresfriends.org>
Date: Wed, 14 Apr 2021 23:47:53 +0200
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On 4/14/21 7:36 PM, Tom Lane wrote:
> Mark Dilger <mark.dilger@enterprisedb.com> writes:
>>> On Apr 13, 2021, at 3:26 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> However I think we may still need an assumption that earthdistance
>>> and cube are in the same schema --- any comments on that?
> 
>> This is probably not worth doing, and we are already past feature
>> freeze, but adding syntax to look up the namespace of an extension might
>> help.
> 
> Yeah, that idea was discussed before (perhaps only in private
> security-team threads, though).  We didn't do anything about it because
> at the time there didn't seem to be pressing need, but in the context
> of SQL function bodies there's an obvious use-case.
> 
>> We could get something like this working just inside the CREATE EXTENSION command if we expanded on the @extschema@ idea a bit.  At first I thought this idea would suffer race conditions with concurrent modifications of pg_extension or pg_namespace, but it looks like we already have a snapshot when processing the script file, so:
> 
>> -CREATE DOMAIN earth AS cube
>> +CREATE DOMAIN @@earthdistance@@::earth AS @@cube@@::cube
> 
> Right, extending the @extschema@ mechanism is what was discussed,
> though I think I'd lean towards something like @extschema:cube@
> to denote the schema of a referenced extension "cube".
> 
> I'm not sure this is useful enough to break feature freeze for,
> but I'm +1 for investigating it for v15.
Just like we have a pseudo "$user" schema, could we have a pseudo
"$extension" catalog?  That should avoid changing grammar rules too much.

CREATE TABLE unaccented_words (
    word "$extension".citext.citext,
    CHECK (word = "$extension".unaccent.unaccent(word)
);

-- 
Vik Fearing