[postgis-devel] PgSQL Extension Dependencies

[Paul Ramsey]

Hey all,
  In trying to fulfill a role as "PostGIS ambassador" to the PgSQL
community, I took the opportunity to canvas developers at the EU conference
last week on topics we raised during our code sprint in Boston last month.
  Dmitri Fontaine, the primary author of the extension framework, was very
attentive to our growing need for some kind of inter-extension dependency
mechanism and potentially a versioning mechanism.
  He proposed a "feature based" solution, which was almost added a few
development cycles ago. (Scroll to the top of the chain to see his
description of the idea.)

https://www.postgresql.org/message-id/flat/CA%2BTgmobe5awu4syu%3DUJJ6skRRuTpcfSGJhg7E1PemWkmGE_qOw%40mail.gmail.com#9e9066a22f8cf2a53edd92fb6c71f71c

This would allow a more granular way of extensions to describe the
capabilities they offer, and for extensions to be reorganized over time.
For example, right now "postgis" provides "geometry", "geography" and
"raster". After 3.0, "postgis" will provide "geometry" and "geography", and
"postgis_raster" will provide "raster" and require "geometry". So there is
a dependency relationship between "postgis_raster" and "postgis" and the
granularity of the features allows them to be moved around between
extensions: a program that required "raster" would still work even after
the extension re-organization, because the "raster" feature would still be
there, just in a different extension.

The only trouble with the feature mechanism I see is that it requires
omniscient developers who know exactly the right granularity to describe
features with.

Have a look at the old patch discussion and provide your feedback and/or
detailed discussion of what you think a feature/dependency/version solution
that would work for us might entail.

Thanks!
P
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