Subject: Re: Support for CREATE MODULE?
To: Jim Mlodgenski <jimmy76@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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From: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Message-ID: <7008facb-7558-ff47-13cd-96d5392f8f5a@enterprisedb.com>
Date: Thu, 3 Jun 2021 14:49:35 +0200
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On 02.06.21 16:43, Jim Mlodgenski wrote:
>> It's already quite hard to tell which part
>> of a multiply.qualified.name is which, given that SQL says that you can
>> optionally put a "catalog" (database) name in front of the others.
>> I really doubt there is a way to shoehorn sub-schemas in there without
>> creating terrible ambiguities.  Is "a.b.c" a reference to object c in
>> schema b in database a, or is it a reference to object c in sub-schema b
>> in schema a?
> That was the area I had the most difficult part to reason about. I tried to make
> some simplifying assumptions by checking if "a" was the current database.
> Since we don't support cross database access, if it was not, I assumed "a"
> was a schema. I not sure if that would be valid, but it did scope things
> to a more manageable problem.

Given that, as you said, the concept of modules is in the SQL standard, 
there is surely some guidance in there about how this is supposed to 
affect name resolution.  So let's start with that.  Maybe we won't like 
it in the end or whatever, but we should surely look there first.