Fix migration bug on v96.go (#10572) (#10574)

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

models/migrations/v96.go

@@ -26,23 +26,38 @@ func deleteOrphanedAttachments(x *xorm.Engine) error {
 	sess := x.NewSession()
 	defer sess.Close()
 
-	err := sess.BufferSize(setting.Database.IterateBufferSize).
-		Where("`issue_id` = 0 and (`release_id` = 0 or `release_id` not in (select `id` from `release`))").Cols("uuid").
-		Iterate(new(Attachment),
-			func(idx int, bean interface{}) error {
-				attachment := bean.(*Attachment)
-
-				if err := os.RemoveAll(models.AttachmentLocalPath(attachment.UUID)); err != nil {
-					return err
-				}
+	var limit = setting.Database.IterateBufferSize
+	if limit <= 0 {
+		limit = 50
+	}
 
-				_, err := sess.ID(attachment.ID).NoAutoCondition().Delete(attachment)
+	for {
+		attachements := make([]Attachment, 0, limit)
+		if err := sess.Where("`issue_id` = 0 and (`release_id` = 0 or `release_id` not in (select `id` from `release`))").
+			Cols("id, uuid").Limit(limit).
+			Asc("id").
+			Find(&attachements); err != nil {
+			return err
+		}
+		if len(attachements) == 0 {
+			return nil
+		}
+
+		var ids = make([]int64, 0, limit)
+		for _, attachment := range attachements {
+			ids = append(ids, attachment.ID)
+		}
+		if _, err := sess.In("id", ids).Delete(new(Attachment)); err != nil {
+			return err
+		}
+
+		for _, attachment := range attachements {
+			if err := os.RemoveAll(models.AttachmentLocalPath(attachment.UUID)); err != nil {
 				return err
-			})
-
-	if err != nil {
-		return err
+			}
+		}
+		if len(attachements) < limit {
+			return nil
+		}
 	}
-
-	return sess.Commit()
 }