[3.2.x] Fixed #32682 -- Made admin changelist use Exists() instead of distinct() for preventing duplicates.

Thanks Zain Patel for the report and Simon Charette for reviews.

The exception introduced in 6307c3f1a123f5975c73b231e8ac4f115fd72c0d
revealed a possible data loss issue in the admin.

Backport of 187118203197801c6cb72dc8b06b714b23b6dd3d from main

1 files changed, 12 insertions, 11 deletions

diff --git a/django/contrib/admin/views/main.py b/django/contrib/admin/views/main.py
index dc43e7849d..a54ef25f23 100644
--- a/django/contrib/admin/views/main.py
+++ b/django/contrib/admin/views/main.py
@@ -17,7 +17,7 @@ from django.core.exceptions import (
     FieldDoesNotExist, ImproperlyConfigured, SuspiciousOperation,
 )
 from django.core.paginator import InvalidPage
-from django.db.models import F, Field, ManyToOneRel, OrderBy
+from django.db.models import Exists, F, Field, ManyToOneRel, OrderBy, OuterRef
 from django.db.models.expressions import Combinable
 from django.urls import reverse
 from django.utils.http import urlencode
@@ -472,13 +472,6 @@ class ChangeList:
             # ValueError, ValidationError, or ?.
             raise IncorrectLookupParameters(e)
 
-        if not qs.query.select_related:
-            qs = self.apply_select_related(qs)
-
-        # Set ordering.
-        ordering = self.get_ordering(request, qs)
-        qs = qs.order_by(*ordering)
-
         # Apply search results
         qs, search_may_have_duplicates = self.model_admin.get_search_results(
             request, qs, self.query,
@@ -491,9 +484,17 @@ class ChangeList:
         )
         # Remove duplicates from results, if necessary
         if filters_may_have_duplicates | search_may_have_duplicates:
-            return qs.distinct()
-        else:
-            return qs
+            qs = qs.filter(pk=OuterRef('pk'))
+            qs = self.root_queryset.filter(Exists(qs))
+
+        # Set ordering.
+        ordering = self.get_ordering(request, qs)
+        qs = qs.order_by(*ordering)
+
+        if not qs.query.select_related:
+            qs = self.apply_select_related(qs)
+
+        return qs
 
     def apply_select_related(self, qs):
         if self.list_select_related is True: