I am working on several packages that depend on postgresql.  These
include for example postgis (which adds GIS capability to the database
system) and other libraries that require connections to the postgresql
backend.  The difficulty is that there now exist several different
postgresql packages, each for a different version of the database
system.  I understand that this is valuable, because it allows
simultaneous installation of multiple database versions which can
expedite the upgrade process.

However, the question is how to handle the set of packages that depend
on postgresql.  At least two solutions are possible.

- Proliferate multiple packages of the packages that depend on
  postgresql, i.e., one per version of the underlying database.  This
  would enable parallel sets of the depending packages, but obviously
  creates many extra packages.

- Introduce some mechanism (e.g., a make variable in mk.conf?) to
  specify which version of postgresql to use when building the
  depending packages.  This would simplify the set of packages, but
  prevents a complete set from coexisting.

Other possibilities might suggest themselves, as well.

I would appreciate suggestions on how to proceed with handling these
packages.  Are there any guidelines that should be followed for
situations like this?

Thanks for your help.

Cheers,
Brook