Migrations fail to apply with postgis 2.0 on remote database

[zejn]

Hi,

Problem lies here: ​https://github.com/django/django/blob/1.8.1/django/contrib/gis/db/backends/postgis/base.py

Beginning with 1.8, the logic to prepare database for test setup has been refactored and the prepare_database() now runs before any migration, not only before tests. This is important, because this now runs even in production.

Since 1.8 supports both Postgis 1.5 and 2.0, the code tries to access the default database, with PostgreSQL this is "postgres" to check the postgis 1.5 template database, specified in POSTGIS_TEMPLATE, actually exists.

I have a production setup using PostgreSQL with Postgis 2.0 on a separate database server. The only accessible database (in pg_hba.conf) for my database user is the database the Django uses. Since code tries to access the database the user does not have access to (postgres), the whole migration process fails.

See ​https://github.com/django/django/commit/bac7664f274be834a09e037331889959f04a75e7 for the relevant changes.

The bug isn't present in master, because the failing query is only used for Postgis 1.5, which is not supported anymore in master, see ​https://github.com/zejn/django/commit/26996e2d55719deb0a0b85c642c88658c929106c

I came up with a simple solution, but it's a bit implicit, see ​https://github.com/zejn/django/commit/acf81f0fe30bff8aa709e37ea10cf63061db4fbc

For the time being I've patched Django.

[Claude Paroz]

This is a duplicate of #24791. Looks like this nodb_connection was not such a good idea.