Get duplicated instances in Django

django_get_duplicated_instances.py

from typing import List

from django.core.exceptions import FieldError
from django.db.models import Count
from django.db.models import Q
from django.db.models import QuerySet


def get_duplicate_instances(queryset: QuerySet, fields: List[str]) -> List[QuerySet]:
    """
    Get duplicate instances of a Django model based on specified fields.

    This function queries the database to identify instances of the given Django model
    that have duplicate values in the specified fields. It returns a list of QuerySets,
    each containing the duplicate instances for a unique combination of field values.
    """

    try:
        values_with_duplicated_instances = (
            queryset.values(*fields).annotate(count=Count("id")).filter(count__gt=1).values(*fields)
        )
    except FieldError as err:
        raise ValueError("One or more of the specified fields do not exist in the model.") from err

    duplicated_instances = []
    for values in values_with_duplicated_instances:
        filters = [Q(**{field_name: field_value}) for field_name, field_value in values.items()]
        duplicated_instances.append(queryset.filter(*filters))
    return duplicated_instances