PostGIS does not work with Postgresql installation

[Gary Johnson]

Hi Guix,

  I need to install the PostGIS spatial extensions into my local
PostgreSQL database. However, due to our unique packaging setup,
PostgreSQL cannot find the PostGIS extension directory.

Here is the error I'm getting from within a psql session:

-------------------------------------------------------------
postgres=# CREATE EXTENSION postgis;

ERROR: could not open extension control file
"/gnu/store/1ybw54pgin4b59czcppybzlk6jkqnxik-postgresql-10.6/share/extension/postgis.control":
No such file or directory
-------------------------------------------------------------

This file is actually installed here:

/gnu/store/nx9lyaia3z8ilxm1z80f7rhg1j3ka1j8-postgis-2.4.4/share/extension/postgis.control

So...the issue is, of course, that Guix is installing PostGIS into its
own directory under /gnu/store rather then into the PostgreSQL install
directory, which is how other package managers do it.

Unfortunately, I can't find any environment variables that I can set to
tell PostgreSQL where to look from the postgis.control file. Instead, it
looks like the *postgis* package under gnu/packages/geo.scm needs to be
rewritten to correctly write out symlinks into the postgresql install
directory.

I don't currently have the Guix programming chops to make this happen.
Perhaps someone else on this mailing list can help?

Thanks,
  Gary