diff --git a/src/tsdb/src/tsdbRead.c b/src/tsdb/src/tsdbRead.c
index cc2b6757fc5b148f3634b338bb15132dd0b1a3a8..056c71e8b8b7c55f37f66c1f01a7a4b58a1ffde6 100644
--- a/src/tsdb/src/tsdbRead.c
+++ b/src/tsdb/src/tsdbRead.c
@@ -1515,7 +1515,8 @@ bool tsdbNextDataBlock(TsdbQueryHandleT* pHandle) {
       pSecQueryHandle->outputCapacity = ((STsdbRepo*)pSecQueryHandle->pTsdb)->config.maxRowsPerFileBlock;
   
       tsdbInitReadHelper(&pSecQueryHandle->rhelper, (STsdbRepo*) pSecQueryHandle->pTsdb);
-  
+      tsdbTakeMemSnapshot(pSecQueryHandle->pTsdb, &pSecQueryHandle->mem, &pSecQueryHandle->imem);
+
       // allocate buffer in order to load data blocks from file
       int32_t numOfCols = QH_GET_NUM_OF_COLS(pQueryHandle);