content: import django.db.models.deletion
  from django.db import migrations, models
  
  
  def populate_denormalized_fields(apps, schema_editor):
      """
      Copy the denormalized fields for _region, _site_group and _site from existing site field.
      """
      Cluster = apps.get_model('virtualization', 'Cluster')
      db_alias = schema_editor.connection.alias
  
      clusters = Cluster.objects.using(db_alias).filter(site__isnull=False).prefetch_related('site')
      for cluster in clusters:
          cluster._region_id = cluster.site.region_id
          cluster._site_group_id = cluster.site.group_id
          cluster._site_id = cluster.site_id
          # Note: Location cannot be set prior to migration
  
      Cluster.objects.using(db_alias).bulk_update(clusters, ['_region', '_site_group', '_site'], batch_size=100)
  
  
  class Migration(migrations.Migration):
      dependencies = [
          ('virtualization', '0044_cluster_scope'),
      ]
  
      operations = [
          migrations.AddField(
              model_name='cluster',
              name='_location',
              field=models.ForeignKey(
                  blank=True,
                  null=True,
                  on_delete=django.db.models.deletion.CASCADE,
                  related_name='_%(class)ss',
                  to='dcim.location',
              ),
          ),
          migrations.AddField(
              model_name='cluster',
              name='_region',
              field=models.ForeignKey(
                  blank=True,
                  null=True,
                  on_delete=django.db.models.deletion.CASCADE,
                  related_name='_%(class)ss',
                  to='dcim.region',
              ),
          ),
          migrations.AddField(
              model_name='cluster',
              name='_site',
              field=models.ForeignKey(
                  blank=True,
                  null=True,
                  on_delete=django.db.models.deletion.CASCADE,
                  related_name='_%(class)ss',
                  to='dcim.site',
              ),
          ),
          migrations.AddField(
              model_name='cluster',
              name='_site_group',
              field=models.ForeignKey(
                  blank=True,
                  null=True,
                  on_delete=django.db.models.deletion.CASCADE,
                  related_name='_%(class)ss',
                  to='dcim.sitegroup',
              ),
          ),
          # Populate denormalized FK values
          migrations.RunPython(code=populate_denormalized_fields, reverse_code=migrations.RunPython.noop),
          migrations.RemoveConstraint(
              model_name='cluster',
              name='virtualization_cluster_unique_site_name',
          ),
          # Delete the site ForeignKey
          migrations.RemoveField(
              model_name='cluster',
              name='site',
          ),
          migrations.AddConstraint(
              model_name='cluster',
              constraint=models.UniqueConstraint(
                  fields=('_site', 'name'), name='virtualization_cluster_unique__site_name'
              ),
          ),
      ]
  
  
  def oc_cluster_remove_site(objectchange, reverting):
      for data in (objectchange.prechange_data, objectchange.postchange_data):
          if data is not None:
              data.pop('site', None)
  
  
  objectchange_migrators = {
      'virtualization.cluster': oc_cluster_remove_site,
  }
  