Use AfterLoad instead of AfterSet on Structs (#2628)

* use AfterLoad instead of AfterSet on Structs

* fix the comments on AfterLoad

* fix the comments on action AfterLoad

vendor/github.com/go-xorm/xorm/session_iterate.go

@@ -23,6 +23,10 @@ func (session *Session) Iterate(bean interface{}, fun IterFunc) error {
 		defer session.Close()
 	}
 
+	if session.statement.bufferSize > 0 {
+		return session.bufferIterate(bean, fun)
+	}
+
 	rows, err := session.Rows(bean)
 	if err != nil {
 		return err
@@ -44,3 +48,49 @@ func (session *Session) Iterate(bean interface{}, fun IterFunc) error {
 	}
 	return err
 }
+
+// BufferSize sets the buffersize for iterate
+func (session *Session) BufferSize(size int) *Session {
+	session.statement.bufferSize = size
+	return session
+}
+
+func (session *Session) bufferIterate(bean interface{}, fun IterFunc) error {
+	if session.isAutoClose {
+		defer session.Close()
+	}
+
+	var bufferSize = session.statement.bufferSize
+	var limit = session.statement.LimitN
+	if limit > 0 && bufferSize > limit {
+		bufferSize = limit
+	}
+	var start = session.statement.Start
+	v := rValue(bean)
+	sliceType := reflect.SliceOf(v.Type())
+	var idx = 0
+	for {
+		slice := reflect.New(sliceType)
+		if err := session.Limit(bufferSize, start).find(slice.Interface(), bean); err != nil {
+			return err
+		}
+
+		for i := 0; i < slice.Elem().Len(); i++ {
+			if err := fun(idx, slice.Elem().Index(i).Addr().Interface()); err != nil {
+				return err
+			}
+			idx++
+		}
+
+		start = start + slice.Elem().Len()
+		if limit > 0 && idx+bufferSize > limit {
+			bufferSize = limit - idx
+		}
+
+		if bufferSize <= 0 || slice.Elem().Len() < bufferSize || idx == limit {
+			break
+		}
+	}
+
+	return nil
+}