old_contents: from django.apps import AppConfig
  from django.db.models.signals import post_delete, post_save
  from wagtail.wagtailsearch.backends import get_search_backends
  from wagtail.wagtailsearch.index import get_indexed_models
  from wagtail.wagtailsearch.signal_handlers import (get_indexed_instance,
                                                     post_delete_signal_handler)
  
  
  def post_save_signal_handler(instance, **kwargs):
      update_fields = kwargs.get('update_fields')
  
      if 'cached_last_updated' in update_fields and 'cached_facebook_count' in update_fields:
          return  # Don't update the search index if we are just updating facebook page counts
  
      indexed_instance = get_indexed_instance(instance)
  
      if indexed_instance:
          for backend in get_search_backends(with_auto_update=True):
              backend.add(indexed_instance)
  
  
  def register_signal_handlers():
      # Loop through list and register signal handlers for each one
      for model in get_indexed_models():
          post_save.connect(post_save_signal_handler, sender=model)
          post_delete.connect(post_delete_signal_handler, sender=model)
  
  
  class CustomWagtailSearchAppConfig(AppConfig):
      name = 'wagtail.wagtailsearch'
      label = 'wagtailsearch'
      verbose_name = "Wagtail search"
  
      def ready(self):
          register_signal_handlers()
  
new_contents: from django.apps import AppConfig
  from django.db.models.signals import post_delete, post_save
  from wagtail.wagtailsearch.backends import get_search_backends
  from wagtail.wagtailsearch.index import get_indexed_models
  from wagtail.wagtailsearch.signal_handlers import (get_indexed_instance,
                                                     post_delete_signal_handler)
  
  
  def post_save_signal_handler(instance, **kwargs):
      update_fields = kwargs.get('update_fields')
  
      social_fields = frozenset(('cached_facebook_count', 'cached_last_updated'))
  
      if update_fields == social_fields:
          return  # Don't update the search index if we are just updating facebook page counts
  
      indexed_instance = get_indexed_instance(instance)
  
      if indexed_instance:
          for backend in get_search_backends(with_auto_update=True):
              backend.add(indexed_instance)
  
  
  def register_signal_handlers():
      # Loop through list and register signal handlers for each one
      for model in get_indexed_models():
          post_save.connect(post_save_signal_handler, sender=model)
          post_delete.connect(post_delete_signal_handler, sender=model)
  
  
  class CustomWagtailSearchAppConfig(AppConfig):
      name = 'wagtail.wagtailsearch'
      label = 'wagtailsearch'
      verbose_name = "Wagtail search"
  
      def ready(self):
          register_signal_handlers()
  
subject: Fix the comparison to work more robustly.