On Wed, 12 Jun 2024 at 18:08, Jelte Fennema-Nio <postg...@jeltef.nl> wrote: > > On Wed, 12 Jun 2024 at 17:50, Andres Freund <and...@anarazel.de> wrote: > > > The OAuth pytest suite makes extensive use of > > > - psycopg, to easily drive libpq; > > > > That's probably not going to fly. It introduces painful circular > > dependencies > > between building postgres (for libpq), building psycopg (requiring libpq) > > and > > testing postgres (requiring psycopg). > > psycopg has a few implementations binary, c, & pure python. The pure > python one can be linked to a specific libpq.so file at runtime[1]. As
This is true, but [citation needed] :D I assume the pointer wanted to be https://www.psycopg.org/psycopg3/docs/api/pq.html#pq-impl I see the following use cases and how I would use psycopg to implement them: - by installing 'psycopg[binary]' you would get a binary bundle shipping with a stable version of the libpq, so you can test the database server regardless of libpq instabilities in the same codebase. - using the pure Python psycopg (enforced by exporting 'PSYCOPG_IMPL=python') you would use the libpq found on the LD_LIBRARY_PATH, which can be useful to test regressions to the libpq itself. - if you want to test new libpq functions you can reach them in Python by dynamic lookup. See [2] for an example of a function only available from libpq v17. [2]: https://github.com/psycopg/psycopg/blob/2bf7783d66ab239a2fa330a842fd461c4bb17c48/psycopg/psycopg/pq/_pq_ctypes.py#L564-L569 -- Daniele
