migrations.py 文件源码

def change_task(self):
        # Task in elixir did not generate a row_type for use as discriminator
        self.schedule('alter', op.add_column, 'task', Column('row_type', String(40)))

        # Task in elixir's queue_id was NULLABLE, but should not be (Tasks HAVE to be in a Queue now)
        self.schedule('alter', op.alter_column, 'task', 'queue_id', nullable=True)

        # Rename of relationship foreign key Task.reserved_by_id -> reserved_by_party_id
        old_name = 'reserved_by_id'
        new_name = 'reserved_by_party_id'
        self.schedule('drop_fk', op.drop_constraint, '%s_%s_fk' % ('task', old_name), 'task')
        self.schedule('alter', op.alter_column, 'task', old_name, new_column_name=new_name)
        self.schedule('create_fk', op.create_foreign_key, fk_name('task', new_name, 'party'), 'task', 'party', [new_name], ['id'])

        self.schedule('drop_pk', op.drop_index, ix_name('task', 'reserved_by_id'))
        self.schedule('indexes', op.create_index, ix_name('task','reserved_by_party_id'), 'task', ['reserved_by_party_id'])