diff --git a/source/dnode/vnode/src/tsdb/tsdbMemTable.c b/source/dnode/vnode/src/tsdb/tsdbMemTable.c
index 26fb39f523c4c9ef2fd868ebb523419cb12c9ff8..8d756618573e50b8161230d69e4b1d271f84ea82 100644
--- a/source/dnode/vnode/src/tsdb/tsdbMemTable.c
+++ b/source/dnode/vnode/src/tsdb/tsdbMemTable.c
@@ -750,7 +750,7 @@ int32_t tsdbRefMemTable(SMemTable *pMemTable, void *pQHandle, _tsdb_reseek_func_
 
   int32_t nRef = atomic_fetch_add_32(&pMemTable->nRef, 1);
   ASSERT(nRef > 0);
-
+  /*
   // register handle (todo: take concurrency in consideration)
   *ppNode = taosMemoryMalloc(sizeof(SQueryNode));
   if (*ppNode == NULL) {
@@ -763,21 +763,21 @@ int32_t tsdbRefMemTable(SMemTable *pMemTable, void *pQHandle, _tsdb_reseek_func_
   (*ppNode)->ppNext = &pMemTable->qList.pNext;
   pMemTable->qList.pNext->ppNext = &(*ppNode)->pNext;
   pMemTable->qList.pNext = *ppNode;
-
+  */
 _exit:
   return code;
 }
 
 int32_t tsdbUnrefMemTable(SMemTable *pMemTable, SQueryNode *pNode) {
   int32_t code = 0;
-
+  /*
   // unregister handle (todo: take concurrency in consideration)
   if (pNode) {
     pNode->pNext->ppNext = pNode->ppNext;
     *pNode->ppNext = pNode->pNext;
     taosMemoryFree(pNode);
   }
-
+  */
   int32_t nRef = atomic_sub_fetch_32(&pMemTable->nRef, 1);
   if (nRef == 0) {
     tsdbMemTableDestroy(pMemTable);
diff --git a/source/dnode/vnode/src/tsdb/tsdbRead.c b/source/dnode/vnode/src/tsdb/tsdbRead.c
index 841396c515ebd4e33386f27c7bd53204ebeab2d8..d8ecaf98323633cba0fe503bf7936294dc178f51 100644
--- a/source/dnode/vnode/src/tsdb/tsdbRead.c
+++ b/source/dnode/vnode/src/tsdb/tsdbRead.c
@@ -3927,6 +3927,7 @@ void tsdbReaderClose(STsdbReader* pReader) {
     pReader->pDelIdx = NULL;
   }
 
+  qTrace("tsdb/reader: %p, untake snapshot", pReader);
   tsdbUntakeReadSnap(pReader, pReader->pReadSnap);
 
   taosThreadMutexDestroy(&pReader->readerMutex);
@@ -4065,6 +4066,7 @@ int32_t tsdbReaderResume(STsdbReader* pReader) {
   //  task snapshot
   int32_t numOfTables = taosHashGetSize(pReader->status.pTableMap);
   if (numOfTables > 0) {
+    qTrace("tsdb/reader: %p, take snapshot", pReader);
     code = tsdbTakeReadSnap(pReader, tsdbSetQueryReseek, &pReader->pReadSnap);
     if (code != TSDB_CODE_SUCCESS) {
       goto _err;
@@ -4392,6 +4394,7 @@ SSDataBlock* tsdbRetrieveDataBlock(STsdbReader* pReader, SArray* pIdList) {
 
   SSDataBlock* ret = doRetrieveDataBlock(pTReader);
 
+  qTrace("tsdb/read-retrieve: %p, unlock read mutex", pReader);
   taosThreadMutexUnlock(&pReader->readerMutex);
 
   return ret;
diff --git a/source/libs/executor/src/scanoperator.c b/source/libs/executor/src/scanoperator.c
index 923b535e63aef06b38364848ba627456b9519292..6dd5341b2e109d0f3fffcfb6233edf6bfe8968ae 100644
--- a/source/libs/executor/src/scanoperator.c
+++ b/source/libs/executor/src/scanoperator.c
@@ -2554,6 +2554,7 @@ static SSDataBlock* getTableDataBlockImpl(void* param) {
   }
 
   STsdbReader* reader = pInfo->base.dataReader;
+  qTrace("tsdb/read-table-data: %p, enter next reader", reader);
   while (tsdbNextDataBlock(reader)) {
     if (isTaskKilled(pTaskInfo)) {
       T_LONG_JMP(pTaskInfo->env, pTaskInfo->code);
@@ -2588,6 +2589,7 @@ static SSDataBlock* getTableDataBlockImpl(void* param) {
     pOperator->resultInfo.totalRows += pBlock->info.rows;
     pInfo->base.readRecorder.elapsedTime += (taosGetTimestampUs() - st) / 1000.0;
 
+    qTrace("tsdb/read-table-data: %p, close reader", reader);
     tsdbReaderClose(pInfo->base.dataReader);
     pInfo->base.dataReader = NULL;
     return pBlock;