content: from django.core.checks import Error, register, Tags
  from django.db.models import Index, UniqueConstraint
  from django.apps import apps
  
  __all__ = (
      'check_duplicate_indexes',
  )
  
  
  @register(Tags.models)
  def check_duplicate_indexes(app_configs, **kwargs):
      """
      Check for an index which is redundant to a declared unique constraint.
      """
      errors = []
  
      for model in apps.get_models():
          if not (meta := getattr(model, "_meta", None)):
              continue
  
          index_fields = {
              tuple(index.fields) for index in getattr(meta, 'indexes', [])
              if isinstance(index, Index)
          }
          constraint_fields = {
              tuple(constraint.fields) for constraint in getattr(meta, 'constraints', [])
              if isinstance(constraint, UniqueConstraint)
          }
  
          # Find overlapping definitions
          if duplicated := index_fields & constraint_fields:
              for fields in duplicated:
                  errors.append(
                      Error(
                          f"Model '{model.__name__}' defines the same field set {fields} in both `Meta.indexes` and "
                          f"`Meta.constraints`.",
                          obj=model,
                      )
                  )
  
      return errors
  