Possible problem with migrations and cascade behavior

using persistent-postgresql, a foreign key reference may not be acting correctly in the presence of CASCADE behavior

setup notes:

1. create table foo (id serial primary key, name text)
2. create table bar (id serial primary key, foo_id integer references foo(id) on delete cascade)

Then with a model file like:

Foo
  name String

Bar
  fooId FooId  

This will assume a default ON UPDATE RESTRICT ON DELETE RESTRICT, and will issue a migration. This migration should alter the constraint, not add one. I'm seeing a create statement locally.

Modifying the fooId field to be fooId FooId OnDelete Cascade is not dismissing that migration.

need to reproduce smaller.

Start by reproducing the migration with persistent-postgresql using the Foo and Bar schemas and the existing CASCADE foreign key described in the issue. Inspect the generated migration and the handling of OnDelete Cascade; done means it alters the existing constraint rather than issuing a create statement, and the migration is dismissed after the model matches the database.