Re: Review: extension template

On 08.07.2013 00:48, Markus Wanner wrote:
> On 07/07/2013 09:51 PM, Dimitri Fontaine wrote:
>> The design we found to address that is
>> called "Extension Templates" and is implemented in the current patch.
>
> I placed my concerns with the proposed implementation. It's certainly
> not the only way how Postgres can manage its extensions. And I still
> hope we can come up with something that's simpler to use and easier to
> understand.

I'm just now dabbling back to this thread after skipping a lot of 
discussion, and I'm disappointed to see that this still seems to be 
running in circles on the same basic question: What exactly is the patch 
trying to accomplish.

The whole point of extensions, as they were originally implemented, is 
to allow them to be managed *outside* the database. In particular, they 
are not included in pg_dump. If you do want them to be included in 
pg_dump, why create it as an extension in the first place? Why not just 
run the create script and create the functions, datatypes etc. directly, 
like you always did before extensions were even invented.

I think the reason is that extensions provide some handy packaging of 
the functions etc, so that you can just do "DROP EXTENSION foo" to get 
rid of all of them. Also, pg_extension table keeps track of the 
currently installed version. Perhaps we need to step back and invent 
another concept that is totally separate from extensions, to provide 
those features. Let's call them "modules". A module is like an 
extension, in that all the objects in the module can be dropped with a 
simple "DROP MODULE foo" command. To create a module, you run "CREATE 
MODULE foo AS <SQL script to create the objects in the module>".

I believe that would be pretty much exactly what Dimitri's original 
inline extension patches did, except that it's not called an extension, 
but a module. I think it's largely been the naming that has been the 
problem with this patch from the very beginning. We came up with the 
concept of templates after we had decided that the originally proposed 
behavior was not what we want from something called extensions. But if 
you rewind to the very beginning, the problem was just with the name. 
The concept was useful, but not something we want to call an extension, 
because the distinguishing feature of an extension is that it lives 
outside the database and is *not* included in pg_dump.

- Heikki