- ('author', models.ForeignKey(verbose_name='author', blank=True, to=settings.AUTH_USER_MODEL, null=True)),
- ('merge_parent', models.ForeignKey(related_name='merge_children', default=None, blank=True, to='catalogue.ChunkChange', null=True, verbose_name='merge parent')),
- ('parent', models.ForeignKey(related_name='children', default=None, blank=True, to='catalogue.ChunkChange', null=True, verbose_name='parent')),
+ ('author', models.ForeignKey(verbose_name='author', blank=True, to=settings.AUTH_USER_MODEL, null=True, on_delete=models.CASCADE)),
+ ('merge_parent', models.ForeignKey(related_name='merge_children', default=None, blank=True, to='catalogue.ChunkChange', null=True, verbose_name='merge parent', on_delete=models.CASCADE)),
+ ('parent', models.ForeignKey(related_name='children', default=None, blank=True, to='catalogue.ChunkChange', null=True, verbose_name='parent', on_delete=models.CASCADE)),