I can't speak for the Django project or Foundation, but would like to
thank you for all of your work on this project!
--
Sam
On 8/3/21 7:01 AM, Daniele Varrazzo wrote:
Hello,
I have maintained psycopg2 in the last >10 years and in the last year I
have been developing a new adapter, Psycopg 3, using the experience made
so far in the area of connecting Python to PostgreSQL.
https://www.psycopg.org/psycopg3/
https://www.psycopg.org/psycopg3/docs/
One of the goals of the project is to make upgrading from psycopg2 easy,
so the project retains the familiar DBAPI 2.0 interface. However, in
order to use more advanced PostgreSQL features (prepared statements,
binary parameters...) it makes use of server-side parameters binding,
which here and there have slightly different behaviour from the
client-side binding used in psycopg2.
I have written a first cut of a Django backend for PostgreSQL based on
Psycopg 3, which is available as an external module at
<https://github.com/dvarrazzo/django-psycopg3-backend>. Using the Django
test suite was immensely helpful to find the missing features and the
different behaviour: thank you very much! As much as I could, I have
changed the adapter to make default choices to reproduce the behaviour
of psycopg2. However there are a few cases where the PostgreSQL-related
code requires some changes, which makes it compatible with both psycopg2
and > 2.
I have a set of changesets, based on the stable/3.2.x branch, which make
the test suite pass with both psycopg 2 and 3; they can be previewed at
<https://github.com/django/django/compare/stable/3.2.x...dvarrazzo:psycopg3-support>.
Most of the changes are import-related, breaking the assumption that
using Postgres implies psycopg2 installed (bopth in the Django code and
in its tests). A few changes are needed to accommodate differences in
the behaviour of PostgreSQL when using server-side binding. A writeup
with the description of these changes is available at
<https://www.psycopg.org/articles/2021/08/02/psycopg3-django-driver/>.
I would like to propose these changes for inclusion in Django. I would
say that the Psycopg 3 backend module should remain an external package
until the adapter becomes more stable and the go-to choice for
PostgreSQL. Some of the changes proposed for Django can be implemented
in different ways: for instance, instead of importing the Range object
from psycopg2 (and now 3, with imports that in my changeset are
conditional), Django could have its own Range object implementation and
the two backends can be configured to use it instead of the
driver-provided ones. Yesterday someone made me aware that the GROUP BY
problem was found in the Oracle backend too and solved in a different
way (https://code.djangoproject.com/ticket/27632).
So, I would like to know, first, if the Django project has interest in
accepting changes with the goal of supporting Psycopg > 2 and
server-side parameters binding for PostgreSQL (which would also help
other potential backends for drivers using the same parameters passing
mechanism, such as asyncpg) and if so what is the best way to propose
them. I can propose a set of stand-alone merge requests, where the code
and the single alternative implementations can be reviewed.
Thank you very much!
-- Daniele
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