Add support "SELECT FOR UPDATE" to orm. Resolve issue #2157

orm/db.go

@@ -310,7 +310,7 @@ func (d *dbBase) InsertStmt(stmt stmtQuerier, mi *modelInfo, ind reflect.Value,
 }
 
 // query sql ,read records and persist in dbBaser.
-func (d *dbBase) Read(q dbQuerier, mi *modelInfo, ind reflect.Value, tz *time.Location, cols []string) error {
+func (d *dbBase) Read(q dbQuerier, mi *modelInfo, ind reflect.Value, tz *time.Location, cols []string, isForUpdate bool) error {
 	var whereCols []string
 	var args []interface{}
 
@@ -341,7 +341,12 @@ func (d *dbBase) Read(q dbQuerier, mi *modelInfo, ind reflect.Value, tz *time.Lo
 	sep = fmt.Sprintf("%s = ? AND %s", Q, Q)
 	wheres := strings.Join(whereCols, sep)
 
-	query := fmt.Sprintf("SELECT %s%s%s FROM %s%s%s WHERE %s%s%s = ?", Q, sels, Q, Q, mi.table, Q, Q, wheres, Q)
+	forUpdate := ""
+	if isForUpdate {
+		forUpdate = "FOR UPDATE"
+	}
+
+	query := fmt.Sprintf("SELECT %s%s%s FROM %s%s%s WHERE %s%s%s = ? %s", Q, sels, Q, Q, mi.table, Q, Q, wheres, Q, forUpdate)
 
 	refs := make([]interface{}, colsNum)
 	for i := range refs {

orm/orm.go

@@ -122,7 +122,17 @@ func (o *orm) getFieldInfo(mi *modelInfo, name string) *fieldInfo {
 // read data to model
 func (o *orm) Read(md interface{}, cols ...string) error {
 	mi, ind := o.getMiInd(md, true)
-	err := o.alias.DbBaser.Read(o.db, mi, ind, o.alias.TZ, cols)
+	err := o.alias.DbBaser.Read(o.db, mi, ind, o.alias.TZ, cols, false)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// read data to model, like Read(), but use "SELECT FOR UPDATE" form
+func (o *orm) ReadForUpdate(md interface{}, cols ...string) error {
+	mi, ind := o.getMiInd(md, true)
+	err := o.alias.DbBaser.Read(o.db, mi, ind, o.alias.TZ, cols, true)
 	if err != nil {
 		return err
 	}
@@ -133,7 +143,7 @@ func (o *orm) Read(md interface{}, cols ...string) error {
 func (o *orm) ReadOrCreate(md interface{}, col1 string, cols ...string) (bool, int64, error) {
 	cols = append([]string{col1}, cols...)
 	mi, ind := o.getMiInd(md, true)
-	err := o.alias.DbBaser.Read(o.db, mi, ind, o.alias.TZ, cols)
+	err := o.alias.DbBaser.Read(o.db, mi, ind, o.alias.TZ, cols, false)
 	if err == ErrNoRows {
 		// Create
 		id, err := o.Insert(md)

orm/qb.go

@@ -19,6 +19,7 @@ import "errors"
 // QueryBuilder is the Query builder interface
 type QueryBuilder interface {
 	Select(fields ...string) QueryBuilder
+	ForUpdate() QueryBuilder
 	From(tables ...string) QueryBuilder
 	InnerJoin(table string) QueryBuilder
 	LeftJoin(table string) QueryBuilder

orm/qb_mysql.go

@@ -34,6 +34,12 @@ func (qb *MySQLQueryBuilder) Select(fields ...string) QueryBuilder {
 	return qb
 }
 
+// ForUpdate add the FOR UPDATE clause
+func (qb *MySQLQueryBuilder) ForUpdate() QueryBuilder {
+	qb.Tokens = append(qb.Tokens, "FOR UPDATE")
+	return qb
+}
+
 // From join the tables
 func (qb *MySQLQueryBuilder) From(tables ...string) QueryBuilder {
 	qb.Tokens = append(qb.Tokens, "FROM", strings.Join(tables, CommaSpace))

orm/qb_tidb.go

@@ -31,6 +31,12 @@ func (qb *TiDBQueryBuilder) Select(fields ...string) QueryBuilder {
 	return qb
 }
 
+// ForUpdate add the FOR UPDATE clause
+func (qb *TiDBQueryBuilder) ForUpdate() QueryBuilder {
+	qb.Tokens = append(qb.Tokens, "FOR UPDATE")
+	return qb
+}
+
 // From join the tables
 func (qb *TiDBQueryBuilder) From(tables ...string) QueryBuilder {
 	qb.Tokens = append(qb.Tokens, "FROM", strings.Join(tables, CommaSpace))

orm/types.go

@@ -45,6 +45,9 @@ type Ormer interface {
 	// 	u = &User{UserName: "astaxie", Password: "pass"}
 	//	err = Ormer.Read(u, "UserName")
 	Read(md interface{}, cols ...string) error
+	// Like Read(), but with "FOR UPDATE" clause, useful in transaction.
+	// Some databases are not support this feature.
+	ReadForUpdate(md interface{}, cols ...string) error
 	// Try to read a row from the database, or insert one if it doesn't exist
 	ReadOrCreate(md interface{}, col1 string, cols ...string) (bool, int64, error)
 	// insert model data to database
@@ -394,7 +397,7 @@ type txEnder interface {
 
 // base database struct
 type dbBaser interface {
-	Read(dbQuerier, *modelInfo, reflect.Value, *time.Location, []string) error
+	Read(dbQuerier, *modelInfo, reflect.Value, *time.Location, []string, bool) error
 	Insert(dbQuerier, *modelInfo, reflect.Value, *time.Location) (int64, error)
 	InsertOrUpdate(dbQuerier, *modelInfo, reflect.Value, *alias, ...string) (int64, error)
 	InsertMulti(dbQuerier, *modelInfo, reflect.Value, int, *time.Location) (int64, error)