diff --git a/src/tsdb/src/tsdbRead.c b/src/tsdb/src/tsdbRead.c
index 93feff9180..145ee5afa5 100644
--- a/src/tsdb/src/tsdbRead.c
+++ b/src/tsdb/src/tsdbRead.c
@@ -72,9 +72,11 @@ typedef struct STableCheckInfo {
   int32_t       compSize;
   int32_t       numOfBlocks;    // number of qualified data blocks not the original blocks
   SDataCols*    pDataCols;
-
   int32_t       chosen;         // indicate which iterator should move forward
   bool          initBuf;        // whether to initialize the in-memory skip list iterator or not
+  SMemTable*    mem;            // in-mem buffer, hold the ref count
+  SMemTable*    imem;           // imem buffer, hold the ref count to avoid release
+
   SSkipListIterator* iter;      // mem buffer skip list iterator
   SSkipListIterator* iiter;     // imem buffer skip list iterator
 } STableCheckInfo;
@@ -247,22 +249,24 @@ static bool initTableMemIterator(STsdbQueryHandle* pHandle, STableCheckInfo* pCh
   
   pCheckInfo->initBuf = true;
   int32_t order = pHandle->order;
-  
+
+  tsdbTakeMemSnapshot(pHandle->pTsdb, &pCheckInfo->mem, &pCheckInfo->imem);
+
   // no data in buffer, abort
-  if (pTable->mem == NULL && pTable->imem == NULL) {
+  if (pCheckInfo->mem == NULL && pCheckInfo->imem == NULL) {
     return false;
   }
   
   assert(pCheckInfo->iter == NULL && pCheckInfo->iiter == NULL);
   
-  if (pTable->mem) {
-    pCheckInfo->iter = tSkipListCreateIterFromVal(pTable->mem->pData, (const char*) &pCheckInfo->lastKey,
-                                                  TSDB_DATA_TYPE_TIMESTAMP, order);
+  if (pCheckInfo->mem) {
+    pCheckInfo->iter = tSkipListCreateIterFromVal(pCheckInfo->mem->tData[pCheckInfo->tableId.tid]->pData,
+        (const char*) &pCheckInfo->lastKey, TSDB_DATA_TYPE_TIMESTAMP, order);
   }
   
-  if (pTable->imem) {
-    pCheckInfo->iiter = tSkipListCreateIterFromVal(pTable->imem->pData, (const char*) &pCheckInfo->lastKey,
-                                                   TSDB_DATA_TYPE_TIMESTAMP, order);
+  if (pCheckInfo->imem) {
+    pCheckInfo->iiter = tSkipListCreateIterFromVal(pCheckInfo->imem->tData[pCheckInfo->tableId.tid]->pData,
+        (const char*) &pCheckInfo->lastKey, TSDB_DATA_TYPE_TIMESTAMP, order);
   }
   
   // both iterators are NULL, no data in buffer right now
@@ -1822,8 +1826,8 @@ static int32_t getAllTableIdList(STable* pSuperTable, SArray* list) {
   while (tSkipListIterNext(iter)) {
     SSkipListNode* pNode = tSkipListIterGet(iter);
     
-    STableIndexElem* elem = (STableIndexElem*)(SL_GET_NODE_DATA((SSkipListNode*) pNode));
-    taosArrayPush(list, &elem->pTable->tableId);
+    STable** pTable = (STable**) SL_GET_NODE_DATA((SSkipListNode*) pNode);
+    taosArrayPush(list, &(*pTable)->tableId);
   }
   
   tSkipListDestroyIter(iter);
@@ -1842,8 +1846,8 @@ static void convertQueryResult(SArray* pRes, SArray* pTableList) {
 
   size_t size = taosArrayGetSize(pTableList);
   for (int32_t i = 0; i < size; ++i) {  // todo speedup  by using reserve space.
-    STableIndexElem* elem = taosArrayGet(pTableList, i);
-    taosArrayPush(pRes, &elem->pTable->tableId);
+    STable* pTable = taosArrayGetP(pTableList, i);
+    taosArrayPush(pRes, &pTable->tableId);
   }
 }
 
@@ -2027,16 +2031,16 @@ SArray* createTableGroup(SArray* pTableList, STSchema* pTagSchema, SColIndex* pC
 bool indexedNodeFilterFp(const void* pNode, void* param) {
   tQueryInfo* pInfo = (tQueryInfo*) param;
   
-  STableIndexElem* elem = (STableIndexElem*)(SL_GET_NODE_DATA((SSkipListNode*)pNode));
+  STable* pTable = *(STable**)(SL_GET_NODE_DATA((SSkipListNode*)pNode));
 
   char*  val = NULL;
   int8_t type = pInfo->sch.type;
 
   if (pInfo->colIndex == TSDB_TBNAME_COLUMN_INDEX) {
-    val = (char*) elem->pTable->name;
+    val = (char*) pTable->name;
     type = TSDB_DATA_TYPE_BINARY;
   } else {
-    val = tdGetKVRowValOfCol(elem->pTable->tagVal, pInfo->sch.colId);
+    val = tdGetKVRowValOfCol(pTable->tagVal, pInfo->sch.colId);
   }
   
   //todo :the val is possible to be null, so check it out carefully
@@ -2092,7 +2096,7 @@ static int32_t doQueryTableList(STable* pSTable, SArray* pRes, tExprNode* pExpr)
       .pExtInfo = pSTable->tagSchema,
       };
 
-  SArray* pTableList = taosArrayInit(8, sizeof(STableIndexElem));
+  SArray* pTableList = taosArrayInit(8, POINTER_BYTES);
 
   tExprTreeTraverse(pExpr, pSTable->pIndex, pTableList, &supp);
   tExprTreeDestroy(&pExpr, destroyHelper);