Re: Converting contrib SQL functions to new style

> On Apr 14, 2021, at 2:47 PM, Vik Fearing <vik@postgresfriends.org> wrote:
>
> 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@
ideaa 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)
> );

Having a single variable $extension might help in many cases, but I don't see how to use it to handle the remaining
cross-extensionreferences, such as earthdistance needing to reference cube. 

—
Mark Dilger
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