Make Update, Updates smart, Only run sql when there are really some new things and reflect changes back to the struct

do.go

@@ -77,7 +77,9 @@ func (s *Do) exec(sql ...string) {
 
 	var err error
 	if len(sql) == 0 {
-		s.sqlResult, err = s.db.Exec(s.sql, s.sqlVars...)
+		if len(s.sql) > 0 {
+			s.sqlResult, err = s.db.Exec(s.sql, s.sqlVars...)
+		}
 	} else {
 		s.sqlResult, err = s.db.Exec(sql[0])
 	}
@@ -108,7 +110,6 @@ func (s *Do) prepareCreateSql() {
 		strings.Join(sqls, ","),
 		s.model.returningStr(),
 	)
-	debug(s.sql)
 	return
 }
 
@@ -145,13 +146,20 @@ func (s *Do) create() {
 	return
 }
 
-func (s *Do) prepareUpdateSql() {
-	update_attrs := s.updateAttrs
-	if len(update_attrs) == 0 {
-		update_attrs = s.model.columnsAndValues("update")
+func (s *Do) prepareUpdateAttrs() (results map[string]interface{}, update bool) {
+	if len(s.updateAttrs) > 0 {
+		results, update = s.model.updatedColumnsAndValues(s.updateAttrs)
+	}
+	return
+}
+
+func (s *Do) prepareUpdateSql(results map[string]interface{}) {
+	var sqls []string
+	for key, value := range results {
+		sqls = append(sqls, fmt.Sprintf("%v = %v", key, s.addToVars(value)))
 	}
 
-	var sqls []string
+	update_attrs := s.model.columnsAndValues("update")
 	for key, value := range update_attrs {
 		sqls = append(sqls, fmt.Sprintf("%v = %v", key, s.addToVars(value)))
 	}
@@ -166,10 +174,20 @@ func (s *Do) prepareUpdateSql() {
 }
 
 func (s *Do) update() {
+	update_attrs := s.updateAttrs
+	if len(update_attrs) > 0 {
+		var need_update bool
+		update_attrs, need_update = s.prepareUpdateAttrs()
+		if !need_update {
+			return
+		}
+	}
+
 	s.err(s.model.callMethod("BeforeUpdate"))
 	s.err(s.model.callMethod("BeforeSave"))
 
-	s.prepareUpdateSql()
+	s.prepareUpdateSql(update_attrs)
+
 	if !s.hasError() {
 		s.exec()
 

gorm_test.go

@@ -717,6 +717,20 @@ func TestUpdate(t *testing.T) {
 	product1 := Product{Code: "123"}
 	product2 := Product{Code: "234"}
 	db.Save(&product1).Save(&product2).Update("code", "456")
+	if product2.Code != "456" {
+		t.Errorf("Object should be updated also with update attributes")
+	}
+
+	db.First(&product1, product1.Id)
+	db.First(&product2, product2.Id)
+	updated_at1 := product1.UpdatedAt
+	updated_at2 := product2.UpdatedAt
+
+	var product3 Product
+	db.First(&product3, product2.Id).Update("code", "456")
+	if updated_at2.Format(time.RFC3339Nano) != product3.UpdatedAt.Format(time.RFC3339Nano) {
+		t.Errorf("updated_at should not be updated if nothing really new")
+	}
 
 	if db.First(&Product{}, "code = '123'").Error != nil {
 		t.Errorf("Product 123's code should not be changed!")
@@ -731,6 +745,13 @@ func TestUpdate(t *testing.T) {
 	}
 
 	db.Table("products").Where("code in (?)", []string{"123"}).Update("code", "789")
+
+	var product4 Product
+	db.First(&product4, product1.Id)
+	if updated_at1.Format(time.RFC3339Nano) != product4.UpdatedAt.Format(time.RFC3339Nano) {
+		t.Errorf("updated_at should be updated if something updated")
+	}
+
 	if db.First(&Product{}, "code = '123'").Error == nil {
 		t.Errorf("Product 123's code should be changed to 789")
 	}
@@ -748,6 +769,20 @@ func TestUpdates(t *testing.T) {
 	product1 := Product{Code: "abc", Price: 10}
 	product2 := Product{Code: "cde", Price: 20}
 	db.Save(&product1).Save(&product2).Updates(map[string]interface{}{"code": "edf", "price": 100})
+	if product2.Code != "edf" || product2.Price != 100 {
+		t.Errorf("Object should be updated also with update attributes")
+	}
+	db.First(&product1, product1.Id)
+	db.First(&product2, product2.Id)
+	updated_at1 := product1.UpdatedAt
+	updated_at2 := product2.UpdatedAt
+
+	var product3 Product
+	db.First(&product3, product2.Id).Updates(map[string]interface{}{"code": "edf", "price": 100})
+
+	if updated_at2.Format(time.RFC3339Nano) != product3.UpdatedAt.Format(time.RFC3339Nano) {
+		t.Errorf("updated_at should not be updated if nothing really new")
+	}
 
 	if db.First(&Product{}, "code = 'abc' and price = 10").Error != nil {
 		t.Errorf("Product abc should not be updated!")
@@ -765,6 +800,11 @@ func TestUpdates(t *testing.T) {
 	if db.First(&Product{}, "code = 'abc'").Error == nil {
 		t.Errorf("Product abc's code should be changed to fgh")
 	}
+	var product4 Product
+	db.First(&product4, product1.Id)
+	if updated_at1.Format(time.RFC3339Nano) != product4.UpdatedAt.Format(time.RFC3339Nano) {
+		t.Errorf("updated_at should be updated if something updated")
+	}
 
 	if db.First(&Product{}, "code = 'edf' and price = ?", 100).Error != nil {
 		t.Errorf("Product cde's code should not be changed to fgh")

model.go

@@ -125,7 +125,45 @@ func (m *Model) columnsHasValue(operation string) (fields []Field) {
 	return
 }
 
+func (m *Model) updatedColumnsAndValues(values map[string]interface{}) (map[string]interface{}, bool) {
+	if m.data == nil {
+		return values, true
+	}
+
+	data := reflect.Indirect(reflect.ValueOf(m.data))
+	results := map[string]interface{}{}
+
+	for key, value := range values {
+		field := data.FieldByName(snakeToUpperCamel(key))
+		if field.IsValid() {
+			if field.Interface() != value {
+				switch field.Kind() {
+				case reflect.Int, reflect.Int32, reflect.Int64:
+					field.SetInt(reflect.ValueOf(value).Int())
+					if field.Int() != reflect.ValueOf(value).Int() {
+						results[key] = value
+					}
+				default:
+					results[key] = value
+					field.Set(reflect.ValueOf(value))
+				}
+			}
+		}
+	}
+
+	field := data.FieldByName("UpdatedAt")
+	if field.IsValid() && values["updated_at"] != nil && len(results) > 0 {
+		data.FieldByName("UpdatedAt").Set(reflect.ValueOf(time.Now()))
+	}
+	result := len(results) > 0
+	return map[string]interface{}{}, result
+}
+
 func (m *Model) columnsAndValues(operation string) map[string]interface{} {
+	if m.data == nil {
+		return map[string]interface{}{}
+	}
+
 	results := map[string]interface{}{}
 	for _, field := range m.fields(operation) {
 		if !field.IsPrimaryKey {