Re: Finer Extension dependencies

On Wed, Mar 28, 2012 at 11:28 AM, Dimitri Fontaine
<dimitri(at)2ndquadrant(dot)fr> wrote:
>> In practice, however, that sounds like a real pain in the neck.  I
>> would expect most people who were packaging extensions to handle a
>> situation like this by forcing the user to provide the name of the
>> function to be called, either via a control table or via a GUC.  And
>> once you've done that, it makes no sense to shove a feature dependency
>> into the extension, because the user might very well just write an
>> appropriate function themselves and tell the extension to call that.
>
> I don't know what you're talking about here, all I can say is that is
> has nothing to do with what the patch is implementing.
>
> What's in the patch is a way to depend on known versions of an extension
> rather than the extension wholesale, whatever the version. Using feature
> dependency allow to avoid 2 particularly messy things:
>
>  - imposing a version numbering scheme with a comparator
>  - maintaining a separate feature matrix
>
> So instead of having to say "foo version 1.2 is now doing buzz"
> and having an extension depend on foo >= 1.2, you can say that your
> extension depends on the buzz feature. That's about it.

Based on this information, it seems that I've misinterpreted the
purpose of the patch. Since extension features seem to live in a
global namespace, I assumed that the purpose of the patch was to allow
both extension A and extension B to provide feature F, and extension C
to depend on F rather than A or B specifically. What I understand you
to be saying here is that's not really what you're trying to
accomplish. Instead, you're just concerned about allowing some but
not all versions of package A to provide feature F, so that other
extensions can depend on F to get the specific version of A that they
need (and not, as I had assumed, so that they can get either A or B).

Let me think more about that. Maybe I'm just easily confused here, or
maybe there is something that should be changed in the code or docs;
I'm not sure yet.

On a more prosaic note, you seem to have made a mistake when
generating the v5 diff. It includes reverts of a couple of unrelated,
recent patches.

> WTF? WTF?

On a further note, I have spent a heck of a lot more time reviewing
other people's patches this CommitFest than you have, and I don't
appreciate this. If you'd rather that I didn't spend time on this
patch, I have plenty of other things to do with my time.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company