diff --git a/kernel/sql/queue.go b/kernel/sql/queue.go
index e3e361f10..e1f613eb3 100644
--- a/kernel/sql/queue.go
+++ b/kernel/sql/queue.go
@@ -17,6 +17,9 @@
 package sql
 
 import (
+	"database/sql"
+	"errors"
+	"fmt"
 	"path"
 	"sync"
 	"time"
@@ -103,57 +106,31 @@ func FlushQueue() {
 		return
 	}
 
+	var execOps int
 	context := map[string]interface{}{eventbus.CtxPushMsg: eventbus.CtxPushMsgToStatusBar}
-	execOps := 0
 	for i, op := range ops {
 		if util.IsExiting {
-			break
-		}
-
-		switch op.action {
-		case "index":
-			err = indexTree(tx, op.box, op.indexPath, context)
-		case "upsert":
-			err = upsertTree(tx, op.upsertTree, context)
-		case "delete":
-			err = batchDeleteByPathPrefix(tx, op.removeTreeBox, op.removeTreePath)
-		case "delete_id":
-			err = deleteByRootID(tx, op.removeTreeID)
-		case "rename":
-			err = batchUpdateHPath(tx, op.renameTree.Box, op.renameTree.ID, op.renameTreeOldHPath, op.renameTree.HPath)
-			if nil != err {
-				break
-			}
-			err = updateRootContent(tx, path.Base(op.renameTree.HPath), op.renameTree.Root.IALAttr("updated"), op.renameTree.ID)
-		case "delete_box":
-			err = deleteByBoxTx(tx, op.box)
-		case "delete_box_refs":
-			err = deleteRefsByBoxTx(tx, op.box)
-		case "insert_refs":
-			err = insertRefs(tx, op.upsertTree)
-		case "update_refs":
-			err = upsertRefs(tx, op.upsertTree)
-		default:
-			logging.LogErrorf("unknown operation [%s]", op.action)
-			break
+			return
 		}
 
+		err = execOp(op, tx, context)
 		execOps++
+
 		if nil != err {
 			logging.LogErrorf("queue operation failed: %s", err)
-			break
+			return
 		}
 
-		if 0 < i && 0 == i%64 {
+		if 0 < i && 0 == execOps%64 {
 			if err = commitTx(tx); nil != err {
 				logging.LogErrorf("commit tx failed: %s", err)
-				break
+				return
 			}
 
 			execOps = 0
 			tx, err = beginTx()
 			if nil != err {
-				break
+				return
 			}
 		}
 	}
@@ -169,6 +146,38 @@ func FlushQueue() {
 	}
 }
 
+func execOp(op *dbQueueOperation, tx *sql.Tx, context map[string]interface{}) (err error) {
+	switch op.action {
+	case "index":
+		err = indexTree(tx, op.box, op.indexPath, context)
+	case "upsert":
+		err = upsertTree(tx, op.upsertTree, context)
+	case "delete":
+		err = batchDeleteByPathPrefix(tx, op.removeTreeBox, op.removeTreePath)
+	case "delete_id":
+		err = deleteByRootID(tx, op.removeTreeID)
+	case "rename":
+		err = batchUpdateHPath(tx, op.renameTree.Box, op.renameTree.ID, op.renameTreeOldHPath, op.renameTree.HPath)
+		if nil != err {
+			break
+		}
+		err = updateRootContent(tx, path.Base(op.renameTree.HPath), op.renameTree.Root.IALAttr("updated"), op.renameTree.ID)
+	case "delete_box":
+		err = deleteByBoxTx(tx, op.box)
+	case "delete_box_refs":
+		err = deleteRefsByBoxTx(tx, op.box)
+	case "insert_refs":
+		err = insertRefs(tx, op.upsertTree)
+	case "update_refs":
+		err = upsertRefs(tx, op.upsertTree)
+	default:
+		msg := fmt.Sprint("unknown operation [%s]", op.action)
+		logging.LogErrorf(msg)
+		err = errors.New(msg)
+	}
+	return
+}
+
 func mergeUpsertTrees() (ops []*dbQueueOperation) {
 	dbQueueLock.Lock()
 	defer dbQueueLock.Unlock()