diff --git a/source/dnode/vnode/src/tsdb/tsdbCache.c b/source/dnode/vnode/src/tsdb/tsdbCache.c
index 2ca52ef5b3c2282e3d108611759f7e0ba02e435c..484020e6e16d75b82b82318f09e23337acebfe4e 100644
--- a/source/dnode/vnode/src/tsdb/tsdbCache.c
+++ b/source/dnode/vnode/src/tsdb/tsdbCache.c
@@ -793,6 +793,9 @@ typedef struct {
   TSDBROW         memRow, imemRow, fsRow;
 
   TsdbNextRowState input[3];
+  SMemTable       *pMemTable;
+  SMemTable       *pIMemTable;
+  STsdb           *pTsdb;
 } CacheNextRowIter;
 
 static int32_t nextRowIterOpen(CacheNextRowIter *pIter, tb_uid_t uid, STsdb *pTsdb) {
@@ -800,16 +803,20 @@ static int32_t nextRowIterOpen(CacheNextRowIter *pIter, tb_uid_t uid, STsdb *pTs
 
   tb_uid_t suid = getTableSuidByUid(uid, pTsdb);
 
+  tsdbTakeMemSnapshot(pTsdb, &pIter->pMemTable, &pIter->pIMemTable);
+
   STbData *pMem = NULL;
-  if (pTsdb->mem) {
-    tsdbGetTbDataFromMemTable(pTsdb->mem, suid, uid, &pMem);
+  if (pIter->pMemTable) {
+    tsdbGetTbDataFromMemTable(pIter->pMemTable, suid, uid, &pMem);
   }
 
   STbData *pIMem = NULL;
-  if (pTsdb->imem) {
-    tsdbGetTbDataFromMemTable(pTsdb->imem, suid, uid, &pIMem);
+  if (pIter->pIMemTable) {
+    tsdbGetTbDataFromMemTable(pIter->pIMemTable, suid, uid, &pIMem);
   }
 
+  pIter->pTsdb = pTsdb;
+
   pIter->pSkyline = taosArrayInit(32, sizeof(TSDBKEY));
 
   SDelIdx delIdx;
@@ -878,6 +885,8 @@ static int32_t nextRowIterClose(CacheNextRowIter *pIter) {
     taosArrayDestroy(pIter->pSkyline);
   }
 
+  tsdbUntakeMemSnapshot(pIter->pTsdb, pIter->pMemTable, pIter->pIMemTable);
+
   return code;
 _err:
   return code;
diff --git a/source/dnode/vnode/src/tsdb/tsdbRead.c b/source/dnode/vnode/src/tsdb/tsdbRead.c
index a09bc32c602dd21e4c92ff1206238eb7e56c2605..d605f564a561d3f02a272c1cbcf696d6dca7d348 100644
--- a/source/dnode/vnode/src/tsdb/tsdbRead.c
+++ b/source/dnode/vnode/src/tsdb/tsdbRead.c
@@ -118,6 +118,8 @@ struct STsdbReader {
   char*              idStr;  // query info handle, for debug purpose
   int32_t            type;   // query type: 1. retrieve all data blocks, 2. retrieve direct prev|next rows
   SBlockLoadSuppInfo suppInfo;
+  SMemTable*         pMem;
+  SMemTable*         pIMem;
 
   SIOCostSummary cost;
   STSchema*      pSchema;
@@ -1847,8 +1849,8 @@ static int32_t initMemDataIterator(STableBlockScanInfo* pBlockScanInfo, STsdbRea
   int32_t backward = (!ASCENDING_TRAVERSE(pReader->order));
 
   STbData* d = NULL;
-  if (pReader->pTsdb->mem != NULL) {
-    tsdbGetTbDataFromMemTable(pReader->pTsdb->mem, pReader->suid, pBlockScanInfo->uid, &d);
+  if (pReader->pMem != NULL) {
+    tsdbGetTbDataFromMemTable(pReader->pMem, pReader->suid, pBlockScanInfo->uid, &d);
     if (d != NULL) {
       code = tsdbTbDataIterCreate(d, &startKey, backward, &pBlockScanInfo->iter.iter);
       if (code == TSDB_CODE_SUCCESS) {
@@ -1868,8 +1870,8 @@ static int32_t initMemDataIterator(STableBlockScanInfo* pBlockScanInfo, STsdbRea
   }
 
   STbData* di = NULL;
-  if (pReader->pTsdb->imem != NULL) {
-    tsdbGetTbDataFromMemTable(pReader->pTsdb->imem, pReader->suid, pBlockScanInfo->uid, &di);
+  if (pReader->pIMem != NULL) {
+    tsdbGetTbDataFromMemTable(pReader->pIMem, pReader->suid, pBlockScanInfo->uid, &di);
     if (di != NULL) {
       code = tsdbTbDataIterCreate(di, &startKey, backward, &pBlockScanInfo->iiter.iter);
       if (code == TSDB_CODE_SUCCESS) {
@@ -2809,6 +2811,8 @@ int32_t tsdbReaderOpen(SVnode* pVnode, SQueryTableDataCond* pCond, SArray* pTabl
     }
   }
 
+  tsdbTakeMemSnapshot(pReader->pTsdb, &pReader->pMem, &pReader->pIMem);
+
   tsdbDebug("%p total numOfTable:%d in this query %s", pReader, numOfTables, pReader->idStr);
   return code;
 
@@ -2824,6 +2828,8 @@ void tsdbReaderClose(STsdbReader* pReader) {
 
   SBlockLoadSuppInfo* pSupInfo = &pReader->suppInfo;
 
+  tsdbUntakeMemSnapshot(pReader->pTsdb, pReader->pMem, pReader->pIMem);
+
   taosMemoryFreeClear(pSupInfo->plist);
   taosMemoryFree(pSupInfo->colIds);