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Subject: Re: Converting contrib SQL functions to new style
From: Mark Dilger <mark.dilger@enterprisedb.com>
In-Reply-To: <3395418.1618352794@sss.pgh.pa.us>
Date: Wed, 14 Apr 2021 10:18:30 -0700
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
 Peter Eisentraut <peter.eisentraut@enterprisedb.com>
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References: <3395418.1618352794@sss.pgh.pa.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
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> On Apr 13, 2021, at 3:26 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>=20
> 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.  The problem seems to be that we can't syntactically refer to the =
schema of an extension.  We have to instead query =
pg_catalog.pg_extension joined against pg_catalog.pg_namespace and then =
interpolate the namespace name into strings that get executed, which is =
ugly.

This syntax is perhaps a non-starter, but conceptually something like:

-CREATE DOMAIN earth AS cube
+CREATE DOMAIN earthdistance::->earth AS cube::->cube

Then we'd perhaps extend RangeVar with an extensionname field and have =
either a schemaname or an extensionname be looked up in places where we =
currently lookup schemas, adding a catcache for extensions.  (Like I =
said, probably not worth doing.)


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

or such, with @@foo@@ being parsed out, looked up in pg_extension join =
pg_namespace, and substituted back in.

=E2=80=94
Mark Dilger
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company