PostgreSQL database introspection does not detect NULL columns

[bthomas@…]

cursor.description does not return the null_ok field, so database introspection does not add null=True to column definitions. The is_nullable column in information_schema.columns does contain this information, however.

[bthomas@…]

Patch to map the is_nullable column from information_schema to the null_ok item in cursor.description

[Malcolm Tredinnick]

Is this valid for both postgreSQL 7.x and 8.x? We support both.

[Bob Thomas <bthomas@…>]

I am only using PostgreSQL 8.x, but I think information_schema was added in PostgreSQL 7.4:

​http://www.postgresql.org/docs/7.4/static/information-schema.html

[Simon Greenhill]

Accepted. Can someone confirm if/what versions of 7.x this works on?

[anonymous]

We tried to setup an environment using PostgreSQL 7.4.30 (the oldest one available for download)[1] to answer your question. Unfortunately when we run manage.py syncdb we received an error message stating that:

"django.db.utils.DatabaseError: function pg_get_serial_sequence("unknown", "unknown") does not exist"

Further research in the django-users mailing list revealed that version 7.4 of PostgreSQL does not contain the function pg_get_serial_sequence.[2] A reply from django core developer Russell Keith-Magee says that in Django version 1.3 support for PostgreSQL 7.4 was abandoned.[3]

[1]​http://www.postgresql.org/ftp/source/
[2]​http://markmail.org/thread/pf4bmphpsv6m4djl
[3]​http://markmail.org/message/tp5czlz3ipy7vd5j

[Aymeric Augustin]

This can't be RFC, the patch doesn't even apply:

trunk % patch -p0 < ~/Downloads/pgnulls.diff
patching file django/db/backends/postgresql_psycopg2/introspection.py
Hunk #1 FAILED at 15.
1 out of 1 hunk FAILED -- saving rejects to file django/db/backends/postgresql_psycopg2/introspection.py.rej

[ricardodani]

This patch is applied to which version? I have the same problem, but using django 1.3 and postgres_psycopg2 driver and this patch can not be applied, just like aaugustin have reported.

[ricardodani]

Same patch, but for django >= 1

[ricardodani]

Added patch to version of django > 1.0

[Claude Paroz]

Patch updated with test

[Ramiro Morales]

In [17508]:

Fixed #7783 -- Made introspection of nullable columns more robust with Postgres.

Thanks bthomas AT ncorcle DOT com for the report and initial patch, and
Claude Paroz for the final, complete patch.