Re: Satisfy extension dependency by one of multiple extensions

Yeb Havinga <yebhavinga@gmail.com> writes:
>> We might want to have a system where an extension can declare that it
>> "provides" capabilites, and then have another extension "require" those
>> capabilities. That would be a neater solution to the case that there are
>> multiple extensions that all provide the same capability.

+1

> Yes that would be neater. I can't think of anything else however than to add
> extprovides' to pg_extension, fill it with an explicit 'provides' from the
> control file when present, or extname otherwise, and use that column to
> check the 'requires' list on extension creation time.

That sounds like a good rough plan.

Then we need to think about maintenance down the road, some releases
from now we will need more features around the same topic.  Debian
control file also has Conflicts and Replaces entries, so that using the
three of them you can handle a smooth upgrade even when the extension
changed its name or has been superseded by a new one which often has the
advantage of being maintained.

Regards,
-- 
Dimitri Fontaine
http://2ndQuadrant.fr     PostgreSQL : Expertise, Formation et Support