diff --git a/src/tsdb/src/tsdbRead.c b/src/tsdb/src/tsdbRead.c
index e410b4d62534560b4541d5d1e39fc95e85a609a8..111fc2019bbcaabe759887948470e8c04256f8ff 100644
--- a/src/tsdb/src/tsdbRead.c
+++ b/src/tsdb/src/tsdbRead.c
@@ -1641,10 +1641,13 @@ static void doMergeTwoLevelData(STsdbQueryHandle* pQueryHandle, STableCheckInfo*
         break;
       }
 
-      // above condition same with key in file
-      if (((pos > endPos || keyFile[pos] > pQueryHandle->window.ekey) && ASCENDING_TRAVERSE(pQueryHandle->order)) ||
-          ((pos < endPos || keyFile[pos] < pQueryHandle->window.ekey) && !ASCENDING_TRAVERSE(pQueryHandle->order))) {
-        break;
+      // break if pos not in this block endPos range. note old code when pos is -1 can crash.
+      if(ASCENDING_TRAVERSE(pQueryHandle->order)) { //ASC
+        if(pos > endPos || keyFile[pos] > pQueryHandle->window.ekey)
+          break;
+      } else { //DESC
+        if(pos < endPos || keyFile[pos] < pQueryHandle->window.ekey)
+          break;
       }
 
       // put keyMem row