update_or_create doesn't understand F() operations

[Marc Tamlyn]

This may not be possible to resolve, but it would be really nice if you could do something like

Foo.objects.update_or_create(name='bar', defaults={'value': F('value') + 1})

This would only be possible when value has a default, and we would need to resolve the F() object to the default. It may be that we need a different object which resolves to an expression when used in an update but resolves differently when used in a create.

[Marc Parizeau]

How about the following?

Foo.objects.update_or_create(name='bar', defaults={'value': Coalesce('value', 0) + 1})

where one could specify an explicit default?

[Simon Charette]

Replying to Marc Parizeau:

How about the following?

Foo.objects.update_or_create(name='bar', defaults={'value': Coalesce('value', 0) + 1})

where one could specify an explicit default?

We'd need to special case Coalesce in update_or_create for this to work as references to columns are not allowed in INSERTs. In other words, Coalesce('value', 0) + 1 exhibits the same limitations that F('value') + 1 has in create.

[Johannes Maron]

Howdy,

I took my good time to look into this issue. I currently have multiple open questions on how this is supposed to work. Excepting this, using the fields' default or db_default value is very opaque IMHO. Since the issue is really old, I believe it warrants a bit more conceptual work in a new-feature issue and possibly a small DEP.

Sorry if this wasn't the outcome you're hoping for, but all good things take time. :)

Cheers
-Joe