diff --git a/src/tsdb/inc/tsdbMemTable.h b/src/tsdb/inc/tsdbMemTable.h
index 3b3f1dd1f6a9307bbe3954374b005a23a9f15ab0..bd64ed4a5238b3b8b60716d8732d59d27218c639 100644
--- a/src/tsdb/inc/tsdbMemTable.h
+++ b/src/tsdb/inc/tsdbMemTable.h
@@ -37,6 +37,7 @@ typedef struct {
   TSKEY      keyLast;
   int64_t    numOfRows;
   SSkipList* pData;
+  T_REF_DECLARE()
 } STableData;
 
 typedef struct {
@@ -76,7 +77,7 @@ typedef struct {
 
 int   tsdbRefMemTable(STsdbRepo* pRepo, SMemTable* pMemTable);
 int   tsdbUnRefMemTable(STsdbRepo* pRepo, SMemTable* pMemTable);
-int   tsdbTakeMemSnapshot(STsdbRepo* pRepo, SMemTable** pMem, SMemTable** pIMem);
+int   tsdbTakeMemSnapshot(STsdbRepo* pRepo, SMemTable** pMem, SMemTable** pIMem, SArray* pATable);
 void  tsdbUnTakeMemSnapShot(STsdbRepo* pRepo, SMemTable* pMem, SMemTable* pIMem);
 void* tsdbAllocBytes(STsdbRepo* pRepo, int bytes);
 int   tsdbAsyncCommit(STsdbRepo* pRepo);
diff --git a/src/tsdb/src/tsdbMemTable.c b/src/tsdb/src/tsdbMemTable.c
index 73a127079920bcdf0cdc2d3e244998310c4d8dbc..6818f2ed14c278bd5d203d0570f52772c159dcde 100644
--- a/src/tsdb/src/tsdbMemTable.c
+++ b/src/tsdb/src/tsdbMemTable.c
@@ -124,17 +124,66 @@ int tsdbUnRefMemTable(STsdbRepo *pRepo, SMemTable *pMemTable) {
   return 0;
 }
 
-int tsdbTakeMemSnapshot(STsdbRepo *pRepo, SMemTable **pMem, SMemTable **pIMem) {
+int tsdbTakeMemSnapshot(STsdbRepo *pRepo, SMemTable **pMem, SMemTable **pIMem, SArray *pATable) {
+  SMemTable *tmem;
+
+  // Get snap object
   if (tsdbLockRepo(pRepo) < 0) return -1;
 
-  *pMem = pRepo->mem;
+  tmem = pRepo->mem;
   *pIMem = pRepo->imem;
-  tsdbRefMemTable(pRepo, *pMem);
+  tsdbRefMemTable(pRepo, tmem);
   tsdbRefMemTable(pRepo, *pIMem);
 
   if (tsdbUnlockRepo(pRepo) < 0) return -1;
 
-  if (*pMem != NULL) taosRLockLatch(&((*pMem)->latch));
+  // Copy mem objects and ref needed STableData
+  if (tmem) {
+    taosRLockLatch(&(tmem->latch));
+
+    *pMem = (SMemTable *)calloc(1, sizeof(**pMem));
+    if (*pMem == NULL) {
+      terrno = TSDB_CODE_TDB_OUT_OF_MEMORY;
+      taosRUnLockLatch(&(tmem->latch));
+      tsdbUnRefMemTable(pRepo, tmem);
+      tsdbUnRefMemTable(pRepo, *pIMem);
+      *pMem = NULL;
+      *pIMem = NULL;
+      return -1;
+    }
+
+    (*pMem)->tData = (STableData **)calloc(tmem->maxTables, sizeof(STableData *));
+    if ((*pMem)->tData == NULL) {
+      terrno = TSDB_CODE_TDB_OUT_OF_MEMORY;
+      taosRUnLockLatch(&(tmem->latch));
+      free(*pMem);
+      tsdbUnRefMemTable(pRepo, tmem);
+      tsdbUnRefMemTable(pRepo, *pIMem);
+      *pMem = NULL;
+      *pIMem = NULL;
+      return -1;
+    }
+
+    (*pMem)->keyFirst = tmem->keyFirst;
+    (*pMem)->keyLast = tmem->keyLast;
+    (*pMem)->numOfRows = tmem->numOfRows;
+    (*pMem)->maxTables = tmem->maxTables;
+
+    for (size_t i = 0; i < taosArrayGetSize(pATable); i++) {
+      STable *    pTable = *(STable **)taosArrayGet(pATable, i);
+      int32_t     tid = TABLE_TID(pTable);
+      STableData *pTableData = (tid < tmem->maxTables) ? tmem->tData[tid] : NULL;
+
+      if ((pTableData == NULL) || (TABLE_UID(pTable) != pTableData->uid)) continue;
+
+      (*pMem)->tData[tid] = tmem->tData[tid];
+      T_REF_INC(tmem->tData[tid]);
+    }
+
+    taosRUnLockLatch(&(tmem->latch));
+  }
+
+  tsdbUnRefMemTable(pRepo, tmem);
 
   tsdbDebug("vgId:%d take memory snapshot, pMem %p pIMem %p", REPO_ID(pRepo), *pMem, *pIMem);
   return 0;
@@ -144,8 +193,14 @@ void tsdbUnTakeMemSnapShot(STsdbRepo *pRepo, SMemTable *pMem, SMemTable *pIMem)
   tsdbDebug("vgId:%d untake memory snapshot, pMem %p pIMem %p", REPO_ID(pRepo), pMem, pIMem);
 
   if (pMem != NULL) {
-    taosRUnLockLatch(&(pMem->latch));
-    tsdbUnRefMemTable(pRepo, pMem);
+    for (size_t i = 0; i < pMem->maxTables; i++) {
+      STableData *pTableData = pMem->tData[i];
+      if (pTableData) {
+        tsdbFreeTableData(pTableData);
+      }
+    }
+    free(pMem->tData);
+    free(pMem);
   }
 
   if (pIMem != NULL) {
@@ -436,7 +491,7 @@ static STableData *tsdbNewTableData(STsdbCfg *pCfg, STable *pTable) {
   STableData *pTableData = (STableData *)calloc(1, sizeof(*pTableData));
   if (pTableData == NULL) {
     terrno = TSDB_CODE_TDB_OUT_OF_MEMORY;
-    goto _err;
+    return NULL;
   }
 
   pTableData->uid = TABLE_UID(pTable);
@@ -449,20 +504,22 @@ static STableData *tsdbNewTableData(STsdbCfg *pCfg, STable *pTable) {
                       tkeyComparFn, pCfg->update ? SL_UPDATE_DUP_KEY : SL_DISCARD_DUP_KEY, tsdbGetTsTupleKey);
   if (pTableData->pData == NULL) {
     terrno = TSDB_CODE_TDB_OUT_OF_MEMORY;
-    goto _err;
+    free(pTableData);
+    return NULL;
   }
 
-  return pTableData;
+  T_REF_INC(pTableData);
 
-_err:
-  tsdbFreeTableData(pTableData);
-  return NULL;
+  return pTableData;
 }
 
 static void tsdbFreeTableData(STableData *pTableData) {
   if (pTableData) {
-    tSkipListDestroy(pTableData->pData);
-    free(pTableData);
+    int32_t ref = T_REF_DEC(pTableData);
+    if (ref == 0) {
+      tSkipListDestroy(pTableData->pData);
+      free(pTableData);
+    }
   }
 }
 
diff --git a/src/tsdb/src/tsdbRead.c b/src/tsdb/src/tsdbRead.c
index 7162f74d3ec2620449066bc28f9acaee64067622..486ff49f097df971d1a1130181a1c14b79f9fc01 100644
--- a/src/tsdb/src/tsdbRead.c
+++ b/src/tsdb/src/tsdbRead.c
@@ -187,13 +187,15 @@ static SArray* getDefaultLoadColumns(STsdbQueryHandle* pQueryHandle, bool loadTS
   return pLocalIdList;
 }
 
-static void tsdbMayTakeMemSnapshot(STsdbQueryHandle* pQueryHandle) {
+static void tsdbMayTakeMemSnapshot(STsdbQueryHandle* pQueryHandle, SArray* psTable) {
   assert(pQueryHandle != NULL && pQueryHandle->pMemRef != NULL);
 
   SMemRef* pMemRef = pQueryHandle->pMemRef;
   if (pQueryHandle->pMemRef->ref++ == 0) {
-    tsdbTakeMemSnapshot(pQueryHandle->pTsdb, (SMemTable**)&(pMemRef->mem), (SMemTable**)&(pMemRef->imem));
+    tsdbTakeMemSnapshot(pQueryHandle->pTsdb, (SMemTable**)&(pMemRef->mem), (SMemTable**)&(pMemRef->imem), psTable);
   }
+
+  taosArrayDestroy(psTable);
 }
 
 static void tsdbMayUnTakeMemSnapshot(STsdbQueryHandle* pQueryHandle) {
@@ -242,7 +244,7 @@ int64_t tsdbGetNumOfRowsInMemTable(TsdbQueryHandleT* pHandle) {
   return rows;
 }
 
-static SArray* createCheckInfoFromTableGroup(STsdbQueryHandle* pQueryHandle, STableGroupInfo* pGroupList, STsdbMeta* pMeta) {
+static SArray* createCheckInfoFromTableGroup(STsdbQueryHandle* pQueryHandle, STableGroupInfo* pGroupList, STsdbMeta* pMeta, SArray** psTable) {
   size_t sizeOfGroup = taosArrayGetSize(pGroupList->pGroupList);
   assert(sizeOfGroup >= 1 && pMeta != NULL);
 
@@ -252,6 +254,12 @@ static SArray* createCheckInfoFromTableGroup(STsdbQueryHandle* pQueryHandle, STa
     return NULL;
   }
 
+  SArray* pTable = taosArrayInit(4, sizeof(STable*));
+  if (pTable == NULL) {
+    taosArrayDestroy(pTableCheckInfo);
+    return NULL;
+  }
+
   // todo apply the lastkey of table check to avoid to load header file
   for (int32_t i = 0; i < sizeOfGroup; ++i) {
     SArray* group = *(SArray**) taosArrayGet(pGroupList->pGroupList, i);
@@ -277,31 +285,40 @@ static SArray* createCheckInfoFromTableGroup(STsdbQueryHandle* pQueryHandle, STa
         assert(info.lastKey <= pQueryHandle->window.skey);
       }
 
+      taosArrayPush(pTable, &pKeyInfo->pTable);
+
       taosArrayPush(pTableCheckInfo, &info);
       tsdbDebug("%p check table uid:%"PRId64", tid:%d from lastKey:%"PRId64" %p", pQueryHandle, info.tableId.uid,
                 info.tableId.tid, info.lastKey, pQueryHandle->qinfo);
     }
   }
 
+  *psTable = pTable;
+
   taosArraySort(pTableCheckInfo, tsdbCheckInfoCompar);
   return pTableCheckInfo;
 }
 
-static SArray* createCheckInfoFromCheckInfo(SArray* pTableCheckInfo, TSKEY skey) {
+static SArray* createCheckInfoFromCheckInfo(SArray* pTableCheckInfo, TSKEY skey, SArray** psTable) {
   size_t si = taosArrayGetSize(pTableCheckInfo);
   SArray* pNew = taosArrayInit(si, sizeof(STableCheckInfo));
   if (pNew == NULL) {
     return NULL;
   }
 
+  SArray* pTable = taosArrayInit(si, sizeof(STable*));
+
   for (int32_t j = 0; j < si; ++j) {
     STableCheckInfo* pCheckInfo = (STableCheckInfo*) taosArrayGet(pTableCheckInfo, j);
     STableCheckInfo info = { .lastKey = skey, .pTableObj = pCheckInfo->pTableObj};
 
     info.tableId = pCheckInfo->tableId;
     taosArrayPush(pNew, &info);
+    taosArrayPush(pTable, &pCheckInfo->pTableObj);
   }
 
+  *psTable = pTable;
+
   // it is ordered already, no need to sort again.
   taosArraySort(pNew, tsdbCheckInfoCompar);
   return pNew;
@@ -332,7 +349,7 @@ static STsdbQueryHandle* tsdbQueryTablesImpl(STsdbRepo* tsdb, STsdbQueryCond* pC
     goto out_of_memory;
   }
 
-  tsdbMayTakeMemSnapshot(pQueryHandle);
+  //tsdbMayTakeMemSnapshot(pQueryHandle);
   assert(pCond != NULL && pCond->numOfCols > 0 && pMemRef != NULL);
 
   if (ASCENDING_TRAVERSE(pCond->order)) {
@@ -393,14 +410,18 @@ TsdbQueryHandleT* tsdbQueryTables(STsdbRepo* tsdb, STsdbQueryCond* pCond, STable
   STsdbMeta* pMeta = tsdbGetMeta(tsdb);
   assert(pMeta != NULL);
 
+  SArray* psTable = NULL;
+
   // todo apply the lastkey of table check to avoid to load header file
-  pQueryHandle->pTableCheckInfo = createCheckInfoFromTableGroup(pQueryHandle, groupList, pMeta);
+  pQueryHandle->pTableCheckInfo = createCheckInfoFromTableGroup(pQueryHandle, groupList, pMeta, &psTable);
   if (pQueryHandle->pTableCheckInfo == NULL) {
     tsdbCleanupQueryHandle(pQueryHandle);
     terrno = TSDB_CODE_TDB_OUT_OF_MEMORY;
     return NULL;
   }
 
+  tsdbMayTakeMemSnapshot(pQueryHandle, psTable);
+
   tsdbDebug("%p total numOfTable:%" PRIzu " in query, %p", pQueryHandle, taosArrayGetSize(pQueryHandle->pTableCheckInfo), pQueryHandle->qinfo);
   return (TsdbQueryHandleT) pQueryHandle;
 }
@@ -2337,12 +2358,18 @@ static int32_t doGetExternalRow(STsdbQueryHandle* pQueryHandle, int16_t type, SM
   pSecQueryHandle = tsdbQueryTablesImpl(pQueryHandle->pTsdb, &cond, pQueryHandle->qinfo, pMemRef);
 
   tfree(cond.colList);
-  pSecQueryHandle->pTableCheckInfo = createCheckInfoFromCheckInfo(pQueryHandle->pTableCheckInfo, pSecQueryHandle->window.skey);
+
+  SArray* psTable = NULL;
+  
+  pSecQueryHandle->pTableCheckInfo = createCheckInfoFromCheckInfo(pQueryHandle->pTableCheckInfo, pSecQueryHandle->window.skey, &psTable);
   if (pSecQueryHandle->pTableCheckInfo == NULL) {
     terrno = TSDB_CODE_QRY_OUT_OF_MEMORY;
     goto out_of_memory;
   }
 
+  
+  tsdbMayTakeMemSnapshot(pSecQueryHandle, psTable);
+
   if (!tsdbNextDataBlock((void*)pSecQueryHandle)) {
     // no result in current query, free the corresponding result rows structure
     if (type == TSDB_PREV_ROW) {