HStoreField example doesn't work

[vedgar]

From ​https://docs.djangoproject.com/en/dev/ref/contrib/postgres/fields/#querying-hstorefield

With given model (Dog), in shell,

>>> from atest.models import Dog
>>> Dog.objects.create(name='Rufus', data={'breed': 'labrador'})

gives "can't adapt type 'dict'" error. After researching, it seems to me it's because noone called psycopg2.extras.register_hstore, that must be called to enable storing dict as hstore in a Postgres database. (If django_hstore is in the list of INSTALLED_APPS, it will call register_hstore by itself, which is probably why it works for some people. But once you remove django_hstore from INSTALLED_APPS, you'll see the bug. Since django_hstore is external app, Django probably shouldn't rely on it.)

I'm not quite sure how to fix it, since I don't know who should be responsible for registering hstore... there is a HStoreExtension operation that does it when migrating, but I have a feeling it should be inserted automatically from makemigrations (when app uses hstore), not shift the burden on users. Even if users are expected to register hstore manually, it should be clearly stated in the docs.

[Tim Graham]

Did you add 'django.contrib.postgres' to INSTALLED_APPS? That should set things up I believe.

[vedgar]

Yes, that's one of first things I did. It didn't help.

[Florian Apolloner]

@vedgar: Can you try remplacing pass with raise in ​https://github.com/django/django/blob/master/django/contrib/postgres/signals.py#L16-L25 ?

[vedgar]

Hm, I changed pass to raise and it worked. Since that didn't make any sense, I changed it back and it still works. I updated django to latest before that, so maybe it was fixed. But it's possible that I made a mistake earlier - sorry for bothering you.

(Just out of curiosity: when makemigrations says "No changes detected", or migrate says "No migrations to apply", is it still possible that something happened to my app? For instance, hstore was registered or something like that.:)

[Sassan Haradji]

I had to run CREATE EXTENSION hstoredict in Postgres shell. Before that it raised the above error even though I had 'django.contrib.postgres' in INSTALLED_APPS.

[Tim Graham]

That step is documented, "Setup the hstore extension in PostgreSQL before the first CreateModel or AddField operation by adding a migration with the HStoreExtension operation. "