Re: Shared access methods?

Andres Freund  writes:
> On 2018-06-14 15:59:22 +0300, Alexander Korotkov wrote:
>> We already have CREATE ACCESS METHOD command.  I think this command
>> should handle that internally.  And I don't understand why "ON
>> CONFLICT DO NOTHING".  If AM with given name already exists in pg_am,
>> why should we ignore the error?

> Well, right now an AM containing extension creates things in each
> database (i.e. same scope as extensions). But with shared AMs that
> wouldn't be the case - you might still want to create the extension in
> another database.  So we'd need to have CREATE ACCESS METHOD check
> whether already is the same entry, and only delete it on DROP ACCESS
> METHOD if there's no dependencies from other databases...

I'm not really buying this idea at all, at least not for index AMs,
because you also need a pile of other database-local infrastructure
--- opclasses, operators, functions, etc.  Trying to make pieces of
that be shared is not going to end well.

			regards, tom lane