Fix: pagination is broken on the dashboard list page (#5516)

* Add test that reproduces issue #5466

* Fix: Duplicate dashboard rows were returned by Dashboard.all() (#5466)

redash/models/__init__.py

@@ -1120,7 +1120,7 @@ def all(cls, org, group_ids, user_id):
                 joinedload(Dashboard.user).load_only(
                     "id", "name", "_profile_image_url", "email"
                 )
-            )
+            ).distinct(Dashboard.created_at, Dashboard.slug)
             .outerjoin(Widget)
             .outerjoin(Visualization)
             .outerjoin(Query)

tests/models/test_dashboards.py

@@ -50,3 +50,32 @@ def test_returns_drafts_by_the_user(self):
         # not using self.assertIn/NotIn because otherwise this fails :O
         self.assertTrue(d in dashboards)
         self.assertFalse(d2 in dashboards)
+
+
+    def test_returns_correct_number_of_dashboards(self):
+        # Solving https://github.com/getredash/redash/issues/5466
+
+        usr = self.factory.create_user()
+
+        ds1 = self.factory.create_data_source()
+        ds2 = self.factory.create_data_source()
+
+        qry1 = self.factory.create_query(data_source=ds1, user=usr)
+        qry2 = self.factory.create_query(data_source=ds2, user=usr)
+
+        viz1 = self.factory.create_visualization(query_rel=qry1, )
+        viz2 = self.factory.create_visualization(query_rel=qry2, )
+
+        def create_dashboard():
+            dash = self.factory.create_dashboard(name="boy howdy", user=usr)
+            self.factory.create_widget(dashboard=dash, visualization=viz1)
+            self.factory.create_widget(dashboard=dash, visualization=viz2)
+
+            return dash
+
+        d1 = create_dashboard()
+        d2 = create_dashboard()
+
+        results = Dashboard.all(self.factory.org, usr.group_ids, usr.id)
+
+        self.assertEqual(2, results.count(), "The incorrect number of dashboards were returned")