Re: How best to load modules?

Hi Dimitri!

PGXS is interesting, but a bigger solution than I was looking for:
ideally, some simple commands for loading the module from my .sql script.

pg_config seems to be in yet another package, postgresql84-devel.  It is a
shell utility for getting such information.  This is again far removed from
the postgresql session, and more bother for the user to install.
Maybe I could run it from the script, regex it for the SHAREDIR key, and
construct from that '$SHAREDIR/contrib'.

A simple variable or function returning the library path would have
solved my present problem.  Perhaps we should make a feature request.

A proper notion of a module (something like the Python import command)
would be really nice, of course, and should already have been there a long
time ago, and it seems to be the aim of the Module_Manager proposal.

Cheers!

On 28.01.11, Dimitri Fontaine wrote:
> Steve White <swhite@aip.de> writes:
> > What are best practices regarding the loading of postgresql modules, say
> > from the contrib/ directory; specifically, with regard to portability?
> >
> > I would like to distribute an SQL script which loads a module, and works
> > with as little further fiddling as possible.
>
> See about PGXS.
>
>   http://www.postgresql.org/docs/9.0/static/xfunc-c.html#XFUNC-C-PGXS
>
> > known options
> > =============
> >
> > Within a session, or in a script, one can use
> >     \i <explicit file path>
> > But within a script this has the weakness that the file path varies from
> > one system distribution to another.
> >
> > One can start psql with
> >     psql ... -f <explicit file path>
> > but that's a measure taken outside the script, to done either with session,
> > or else be done by a further measure such as a shell script.
> >
> > Ideally, the location of the default modules directory (or installation
> > directory) should be available within a session in some variable or from
> > some function call.
>
> You can use pg_config to get this PATH, and in recent versions of
> PostgreSQL you can use $libdir as the module directory name.
>
>   select name, setting from pg_settings where name ~ 'dynamic_library_path';
>
> > There has been talk about a bigger solution on
> >     http://wiki.postgresql.org/wiki/Module_Manager
> > but little seems to have happened there in some years.
>
> It seemed stalled for a long time because the harder part of this
> development was to get an agreement among hackers about what to develop
> exactly.  We've been slowly reaching that between developer meetings in
> 2009 and 2010, and the result should hit the official source tree before
> the next developer meeting in 2011 :)
>
>   https://commitfest.postgresql.org/action/patch_view?id=471
>   https://commitfest.postgresql.org/action/patch_view?id=472
>
> If you want to see more details about the expected-to-be-commited-soon
> development work, have a look there:
>
>   http://pgsql.tapoueh.org/extensions/doc/html/extend-extension.html
>
> If you have enough time and interest into the feature, you can even
> clone the git repository where the development occurs (branches named
> "extension" and "upgrade") and try it for yourself, then maybe send a
> mail about your findings (we call that a review):
>
>   http://git.postgresql.org/gitweb?p=postgresql-extension.git;a=summary
>   http://wiki.postgresql.org/wiki/Reviewing_a_Patch
>
> Regards,
> --
> Dimitri Fontaine
> http://2ndQuadrant.fr     PostgreSQL : Expertise, Formation et Support
>

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