Fix preload duplicates has many related objects

callback_query_preload.go

@@ -186,13 +186,6 @@ func (scope *Scope) handleHasManyPreload(field *Field, conditions []interface{})
 		for j := 0; j < indirectScopeValue.Len(); j++ {
 			object := indirect(indirectScopeValue.Index(j))
 			objectRealValue := getValueFromFields(object, relation.AssociationForeignFieldNames)
-			if j > 0 {
-				prevObject := indirect(indirectScopeValue.Index(j - 1))
-				prevObjectRealValue := getValueFromFields(prevObject, relation.AssociationForeignFieldNames)
-				if toString(prevObjectRealValue) == toString(objectRealValue) {
-					continue
-				}
-			}
 			if results, ok := preloadMap[toString(objectRealValue)]; ok {
 				f := object.FieldByName(field.Name)
 				f.Set(reflect.Append(f, results...))

preload_test.go

@@ -1513,19 +1513,23 @@ func TestPrefixedPreloadDuplication(t *testing.T) {
 	type (
 		Level4 struct {
 			ID       uint
+			Name     string
 			Level3ID uint
 		}
 		Level3 struct {
 			ID      uint
+			Name    string
 			Level4s []*Level4
 		}
 		Level2 struct {
 			ID       uint
+			Name     string
 			Level3ID sql.NullInt64 `sql:"index"`
 			Level3   *Level3
 		}
 		Level1 struct {
 			ID       uint
+			Name     string
 			Level2ID sql.NullInt64 `sql:"index"`
 			Level2   *Level2
 		}
@@ -1540,7 +1544,7 @@ func TestPrefixedPreloadDuplication(t *testing.T) {
 		t.Error(err)
 	}
 
-	lvl := new(Level3)
+	lvl := &Level3{}
 	if err := DB.Save(lvl).Error; err != nil {
 		t.Error(err)
 	}

scope.go

@@ -1237,6 +1237,7 @@ func (scope *Scope) getColumnAsScope(column string) *Scope {
 				fieldType = fieldType.Elem()
 			}
 
+			resultsMap := map[interface{}]bool{}
 			results := reflect.New(reflect.SliceOf(reflect.PtrTo(fieldType))).Elem()
 
 			for i := 0; i < indirectScopeValue.Len(); i++ {
@@ -1244,11 +1245,13 @@ func (scope *Scope) getColumnAsScope(column string) *Scope {
 
 				if result.Kind() == reflect.Slice {
 					for j := 0; j < result.Len(); j++ {
-						if elem := result.Index(j); elem.CanAddr() {
+						if elem := result.Index(j); elem.CanAddr() && resultsMap[elem.Addr()] != true {
+							resultsMap[elem.Addr()] = true
 							results = reflect.Append(results, elem.Addr())
 						}
 					}
-				} else if result.CanAddr() {
+				} else if result.CanAddr() && resultsMap[result.Addr()] != true {
+					resultsMap[result.Addr()] = true
 					results = reflect.Append(results, result.Addr())
 				}
 			}