feat: Custom filter for admin to locate duplicate records

postcards/admin.py

@@ -6,6 +6,7 @@
 from django.utils.html import format_html
 from import_export.admin import ExportMixin
 
+from .filters import DuplicateFilter
 from .models import (
     Censor,
     Image,
@@ -159,6 +160,7 @@ class ObjectAdmin(ExportMixin, admin.ModelAdmin):
         "date_of_correspondence",
         "regime_censor",
         "regime_location",
+        DuplicateFilter,
     )
     filter_horizontal = ("postmark",)
     extra = 1

postcards/filters.py

@@ -1,5 +1,6 @@
 import django_filters
 from dateutil.parser import parse
+from django.contrib.admin import SimpleListFilter
 from django.db.models import Q
 from django.shortcuts import render
 
@@ -51,6 +52,27 @@ def __init__(self, *args, **kwargs):
         ).distinct()
 
 
+class DuplicateFilter(SimpleListFilter):
+    """this filter is used inside of django-admin to find duplicate files"""
+
+    title = "Duplicates"
+    parameter_name = "item_id"
+
+    def lookups(self, request, model_admin):
+        return (("true", "Duplicates"),)
+
+    def queryset(self, request, queryset):
+        if self.value():
+            return queryset
+        if self.value() is not None:
+            if self.value().lower() == "duplicates":
+                return queryset.filter().exclude(
+                    id__in=[
+                        i.id for i in queryset.distinct("item_id").order_by("item_id")
+                    ]
+                )
+
+
 class ObjectFilter(django_filters.FilterSet):
     class Meta:
         model = Object