[6.x] Only restore common relations

src/Illuminate/Database/Eloquent/Collection.php

@@ -557,7 +557,7 @@ public function getQueueableIds()
      */
     public function getQueueableRelations()
     {
-        return $this->isNotEmpty() ? $this->first()->getQueueableRelations() : [];
+        return $this->isEmpty() ? [] : array_intersect(...$this->map->getQueueableRelations()->all());
     }
 
     /**

tests/Database/DatabaseEloquentCollectionTest.php

@@ -422,6 +422,24 @@ public function testQueueableCollectionImplementationThrowsExceptionOnMultipleMo
         $c->getQueueableClass();
     }
 
+    public function testQueueableRelationshipsReturnsOnlyRelationsCommonToAllModels()
+    {
+        // This is needed to prevent loading non-existing relationships on polymorphic model collections (#26126)
+        $c = new Collection([new class {
+            public function getQueueableRelations()
+            {
+                return ['user'];
+            }
+        }, new class {
+            public function getQueueableRelations()
+            {
+                return ['user', 'comments'];
+            }
+        }]);
+
+        $this->assertEquals(['user'], $c->getQueueableRelations());
+    }
+
     public function testEmptyCollectionStayEmptyOnFresh()
     {
         $c = new Collection;