diff --git a/source/dnode/vnode/src/tsdb/tsdbMergeTree.c b/source/dnode/vnode/src/tsdb/tsdbMergeTree.c
index 8e018300e7..4d54fbbd79 100644
--- a/source/dnode/vnode/src/tsdb/tsdbMergeTree.c
+++ b/source/dnode/vnode/src/tsdb/tsdbMergeTree.c
@@ -101,12 +101,22 @@ void *destroyLastBlockLoadInfo(SSttBlockLoadInfo *pLoadInfo) {
 static SBlockData *loadLastBlock(SLDataIter *pIter, const char *idStr) {
   int32_t code = 0;
 
-  SSttBlockLoadInfo *pInfo = pIter->pBlockLoadInfo;
-  if (pInfo->blockIndex[0] == pIter->iSttBlk) {
+  SSttBlockLoadInfo* pInfo = pIter->pBlockLoadInfo;
+  if (pInfo->blockIndex[0]  == pIter->iSttBlk) {
+    if (pInfo->currentLoadBlockIndex != 0) {
+      tsdbDebug("current load index is set to 0, block index:%d, file index:%d, due to uid:%" PRIu64 ", load data, %s",
+                pIter->iSttBlk, pIter->iStt, pIter->uid, idStr);
+      pInfo->currentLoadBlockIndex = 0;
+    }
     return &pInfo->blockData[0];
   }
 
   if (pInfo->blockIndex[1] == pIter->iSttBlk) {
+    if (pInfo->currentLoadBlockIndex != 1) {
+      tsdbDebug("current load index is set to 1, block index:%d, file index:%d, due to uid:%"PRIu64", load data, %s",
+                pIter->iSttBlk, pIter->iStt, pIter->uid, idStr);
+      pInfo->currentLoadBlockIndex = 1;
+    }
     return &pInfo->blockData[1];
   }
 
@@ -130,13 +140,15 @@ static SBlockData *loadLastBlock(SLDataIter *pIter, const char *idStr) {
     pInfo->elapsedTime += el;
     pInfo->loadBlocks += 1;
 
-    tsdbDebug("read last block, index:%d, last file index:%d, elapsed time:%.2f ms, %s", pIter->iSttBlk, pIter->iStt,
-              el, idStr);
+    tsdbDebug("read last block, total load:%d, trigger by uid:%"PRIu64", last file index:%d, last block index:%d, entry:%d, %p, elapsed time:%.2f ms, %s",
+              pInfo->loadBlocks, pIter->uid, pIter->iStt, pIter->iSttBlk, pInfo->currentLoadBlockIndex, pBlock, el, idStr);
     if (code != TSDB_CODE_SUCCESS) {
       goto _exit;
     }
 
     pInfo->blockIndex[pInfo->currentLoadBlockIndex] = pIter->iSttBlk;
+    tsdbDebug("last block index list:%d, %d, %s", pInfo->blockIndex[0], pInfo->blockIndex[1], idStr);
+
     pIter->iRow = (pIter->backward) ? pInfo->blockData[pInfo->currentLoadBlockIndex].nRow : -1;
   }
 
@@ -324,8 +336,10 @@ _exit:
 
 void tLDataIterClose(SLDataIter *pIter) { taosMemoryFree(pIter); }
 
-void tLDataIterNextBlock(SLDataIter *pIter) {
+void tLDataIterNextBlock(SLDataIter *pIter, const char* idStr) {
   int32_t step = pIter->backward ? -1 : 1;
+  int32_t oldIndex = pIter->iSttBlk;
+
   pIter->iSttBlk += step;
 
   int32_t index = -1;
@@ -372,6 +386,10 @@ void tLDataIterNextBlock(SLDataIter *pIter) {
   if (index != -1) {
     pIter->iSttBlk = index;
     pIter->pSttBlk = (SSttBlk *)taosArrayGet(pIter->pBlockLoadInfo->aSttBlk, pIter->iSttBlk);
+    tsdbDebug("try next last file block:%d from %d, trigger by uid:%"PRIu64", file index:%d, %s", pIter->iSttBlk, oldIndex, pIter->uid, pIter->iStt,
+        idStr);
+  } else {
+    tsdbDebug("no more last block qualified, uid:%"PRIu64", file index::%d, %s", pIter->uid, oldIndex, idStr);
   }
 }
 
@@ -396,16 +414,10 @@ static void findNextValidRow(SLDataIter *pIter, const char *idStr) {
   for (; i < pBlockData->nRow && i >= 0; i += step) {
     if (pBlockData->aUid != NULL) {
       if (!pIter->backward) {
-        /*if (pBlockData->aUid[i] < pIter->uid) {
-          continue;
-        } else */
         if (pBlockData->aUid[i] > pIter->uid) {
           break;
         }
       } else {
-        /*if (pBlockData->aUid[i] > pIter->uid) {
-          continue;
-        } else */
         if (pBlockData->aUid[i] < pIter->uid) {
           break;
         }
@@ -461,7 +473,7 @@ bool tLDataIterNextRow(SLDataIter *pIter, const char *idStr) {
     findNextValidRow(pIter, idStr);
 
     if (pIter->iRow >= pBlockData->nRow || pIter->iRow < 0) {
-      tLDataIterNextBlock(pIter);
+      tLDataIterNextBlock(pIter, idStr);
       if (pIter->pSttBlk == NULL) {  // no more data
         goto _exit;
       }
diff --git a/source/dnode/vnode/src/tsdb/tsdbRead.c b/source/dnode/vnode/src/tsdb/tsdbRead.c
index 1ed050f64f..4bb1f2d2fe 100644
--- a/source/dnode/vnode/src/tsdb/tsdbRead.c
+++ b/source/dnode/vnode/src/tsdb/tsdbRead.c
@@ -1645,6 +1645,7 @@ static int32_t doMergeFileBlockAndLastBlock(SLastBlockReader* pLastBlockReader,
   STSRow*    pTSRow = NULL;
   SRowMerger merge = {0};
   TSDBROW    fRow = tMergeTreeGetRow(&pLastBlockReader->mergeTree);
+  tsdbTrace("fRow ptr:%p, %d, uid:%"PRIu64", %s", fRow.pBlockData, fRow.iRow, pLastBlockReader->uid, pReader->idStr);
 
   // only last block exists
   if ((!mergeBlockData) || (tsLastBlock != pBlockData->aTSKEY[pDumpInfo->rowIndex])) {