Re: Converting contrib SQL functions to new style

On 4/14/21 7:36 PM, Tom Lane wrote:
> Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com> writes:
>>> On Apr 13, 2021, at 3:26 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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