Test ManyToMany relations with multi primary keys

association.go

@@ -40,6 +40,7 @@ func (association *Association) Append(values ...interface{}) *Association {
 			association.setErr(errors.New("invalid association type"))
 		}
 	}
+	scope.Search.Select(association.Column)
 	scope.callCallbacks(scope.db.parent.callback.updates)
 	return association.setErr(scope.db.Error)
 }

callback_update.go

@@ -64,6 +64,7 @@ func Update(scope *Scope) {
 			}
 		}
 
+		if len(sqls) > 0 {
 			scope.Raw(fmt.Sprintf(
 				"UPDATE %v SET %v %v",
 				scope.QuotedTableName(),
@@ -72,6 +73,7 @@ func Update(scope *Scope) {
 			))
 			scope.Exec()
 		}
+	}
 }
 
 func AfterUpdate(scope *Scope) {

join_table_handler.go

@@ -36,26 +36,39 @@ func (s *JoinTableHandler) Setup(relationship *Relationship, tableName string, s
 
 	s.Source = JoinTableSource{ModelType: source}
 	sourceScope := &Scope{Value: reflect.New(source).Interface()}
-	for _, primaryField := range sourceScope.GetModelStruct().PrimaryFields {
+	sourcePrimaryFields := sourceScope.GetModelStruct().PrimaryFields
+	for _, primaryField := range sourcePrimaryFields {
 		if relationship.ForeignDBName == "" {
 			relationship.ForeignFieldName = source.Name() + primaryField.Name
 			relationship.ForeignDBName = ToDBName(relationship.ForeignFieldName)
 		}
+
+		var dbName string
+		if len(sourcePrimaryFields) == 1 || primaryField.DBName == "id" {
+			dbName = relationship.ForeignDBName
+		} else {
+			dbName = ToDBName(source.Name() + primaryField.Name)
+		}
+
 		s.Source.ForeignKeys = append(s.Source.ForeignKeys, JoinTableForeignKey{
-			DBName:            relationship.ForeignDBName,
+			DBName:            dbName,
 			AssociationDBName: primaryField.DBName,
 		})
 	}
 
 	s.Destination = JoinTableSource{ModelType: destination}
 	destinationScope := &Scope{Value: reflect.New(destination).Interface()}
-	for _, primaryField := range destinationScope.GetModelStruct().PrimaryFields {
-		if relationship.AssociationForeignDBName == "" {
-			relationship.AssociationForeignFieldName = destination.Name() + primaryField.Name
-			relationship.AssociationForeignDBName = ToDBName(relationship.AssociationForeignFieldName)
+	destinationPrimaryFields := destinationScope.GetModelStruct().PrimaryFields
+	for _, primaryField := range destinationPrimaryFields {
+		var dbName string
+		if len(sourcePrimaryFields) == 1 || primaryField.DBName == "id" {
+			dbName = relationship.AssociationForeignDBName
+		} else {
+			dbName = ToDBName(destinationScope.GetModelStruct().ModelType.Name() + primaryField.Name)
 		}
+
 		s.Destination.ForeignKeys = append(s.Destination.ForeignKeys, JoinTableForeignKey{
-			DBName:            relationship.AssociationForeignDBName,
+			DBName:            dbName,
 			AssociationDBName: primaryField.DBName,
 		})
 	}

multi_primary_keys_test.go

@@ -0,0 +1,46 @@
+package gorm_test
+
+import (
+	"fmt"
+	"os"
+	"testing"
+)
+
+type Blog struct {
+	ID      uint   `gorm:"primary_key"`
+	Locale  string `gorm:"primary_key"`
+	Subject string
+	Body    string
+	Tags    []Tag `gorm:"many2many:blog_tags;"`
+}
+
+type Tag struct {
+	ID     uint   `gorm:"primary_key"`
+	Locale string `gorm:"primary_key"`
+	Value  string
+}
+
+func TestManyToManyWithMultiPrimaryKeys(t *testing.T) {
+	if dialect := os.Getenv("GORM_DIALECT"); dialect != "sqlite" {
+		DB.Exec(fmt.Sprintf("drop table blog_tags;"))
+		DB.AutoMigrate(&Blog{}, &Tag{})
+		blog := Blog{
+			Locale:  "ZH",
+			Subject: "subject",
+			Body:    "body",
+			Tags: []Tag{
+				{Locale: "ZH", Value: "tag1"},
+				{Locale: "ZH", Value: "tag2"},
+			},
+		}
+
+		DB.Save(&blog)
+		DB.Model(&blog).Association("Tags").Append([]Tag{{Locale: "ZH", Value: "tag3"}})
+
+		var tags []Tag
+		DB.Model(&blog).Related(&tags, "Tags")
+		if len(tags) != 3 {
+			t.Errorf("should found 3 tags with blog")
+		}
+	}
+}