NOT NULL Constraint for polymorphic_ctype_id?

[guettli]

Hi,

some how I got rows which had NULL in polymorphic_ctype_id.

AFAIK this makes no sense.

Why not make a non null constraint on this column?

What do you think?

[vdboor]

The null requirement is needed, so projects can upgrade to polymorphic, and set the value afterwards.

If the value is null, it likely means you did something like:

• adding polymorphic later.
• imported fixtures
• bypassed the regular save() (or only used save_base())
• removed a ContentType, and set the value to null.

[TZanke]

In my opinion, polymorphic should keep my production databases in a consistent state. Allowing Null in the database, breaking the polymorphic plugin, sounds not ideal.

My solution to support both, consistent database and upgrading users would be:

polymorphic_ctype = models.ForeignKey(ContentType, null=False,...)
within the polymorphic plugin.

And for users upgrading:

class Demo(Polymorphic):
   ...

Demo._meta.get_field('polymorphic_ctype').null = True

[NotSqrt]

Hi,

I just faced this problem :
When creating instances inside a migration, Django does not give access to the polymorphic manager and other overridable model methods.
That means that save() won't add the polymorphic_ctype automatically, and since the DB says that NULL is acceptable, no integrity exception is raised.

I really want to add this not null constraint to avoid future similar problems !

Thanks !

[vdboor]

good point @NotSqrt I'll reopen this issue so someone can look into this.
I'll accept a pull request that both fixes this issue, and provides the documentation bits to help people migrate to polymorphic. Your migrations will likely fail after all when you add the polymorphic_ctype_id as NOT NULL - it needs to have a default.