diff --git a/source/dnode/vnode/src/tsdb/tsdbRead.c b/source/dnode/vnode/src/tsdb/tsdbRead.c
index baa985fb24..e94cdfde37 100644
--- a/source/dnode/vnode/src/tsdb/tsdbRead.c
+++ b/source/dnode/vnode/src/tsdb/tsdbRead.c
@@ -1362,15 +1362,10 @@ static void getBlockToLoadInfo(SDataBlockToLoadInfo* pInfo, SFileDataBlockInfo*
   pInfo->hasDupTs = (pBlock->nSubBlock == 1) ? pBlock->hasDup : true;
   pInfo->overlapWithDelInfo = overlapWithDelSkyline(pScanInfo, pBlock, pReader->order);
 
-  // todo here we need to each key in the last files to identify if it is really overlapped with last block
-  // todo
-  bool overlapWithlastBlock = false;
-#if 0
-  if (taosArrayGetSize(pLastBlockReader->pSstBlk) > 0 && (pLastBlockReader->currentBlockIndex != -1)) {
-    SSttBlk* pSstBlk = taosArrayGet(pLastBlockReader->pSstBlk, pLastBlockReader->currentBlockIndex);
-    overlapWithlastBlock = !(pBlock->maxKey.ts < pSstBlk->minKey || pBlock->minKey.ts > pSstBlk->maxKey);
+  if (hasDataInLastBlock(pLastBlockReader)) {
+    int64_t tsLast = getCurrentKeyInLastBlock(pLastBlockReader);
+    pInfo->overlapWithLastBlock = !(pBlock->maxKey.ts < tsLast || pBlock->minKey.ts > tsLast);
   }
-#endif
 
   pInfo->moreThanCapcity = pBlock->nRow > pReader->capacity;
   pInfo->partiallyRequired = dataBlockPartiallyRequired(&pReader->window, &pReader->verRange, pBlock);
@@ -1896,151 +1891,6 @@ static int32_t doMergeMultiLevelRows(STsdbReader* pReader, STableBlockScanInfo*
   return code;
 }
 
-#if 0
-static int32_t doMergeThreeLevelRows(STsdbReader* pReader, STableBlockScanInfo* pBlockScanInfo, SBlockData* pBlockData) {
-  SRowMerger merge = {0};
-  STSRow*    pTSRow = NULL;
-
-  SFileBlockDumpInfo* pDumpInfo = &pReader->status.fBlockDumpInfo;
-  SArray*             pDelList = pBlockScanInfo->delSkyline;
-
-  TSDBROW* pRow = getValidMemRow(&pBlockScanInfo->iter, pDelList, pReader);
-  TSDBROW* piRow = getValidMemRow(&pBlockScanInfo->iiter, pDelList, pReader);
-  ASSERT(pRow != NULL && piRow != NULL);
-
-  int64_t key = pBlockData->aTSKEY[pDumpInfo->rowIndex];
-  bool    freeTSRow = false;
-
-  uint64_t uid = pBlockScanInfo->uid;
-
-  TSDBKEY k = TSDBROW_KEY(pRow);
-  TSDBKEY ik = TSDBROW_KEY(piRow);
-  if (ASCENDING_TRAVERSE(pReader->order)) {
-    // [1&2] key <= [k.ts && ik.ts]
-    if (key <= k.ts && key <= ik.ts) {
-      TSDBROW fRow = tsdbRowFromBlockData(pBlockData, pDumpInfo->rowIndex);
-      tRowMergerInit(&merge, &fRow, pReader->pSchema);
-
-      doMergeRowsInFileBlocks(pBlockData, pBlockScanInfo, pReader, &merge);
-
-      if (ik.ts == key) {
-        tRowMerge(&merge, piRow);
-        doMergeRowsInBuf(&pBlockScanInfo->iiter, uid, key, pBlockScanInfo->delSkyline, &merge, pReader);
-      }
-
-      if (k.ts == key) {
-        tRowMerge(&merge, pRow);
-        doMergeRowsInBuf(&pBlockScanInfo->iter, uid, key, pBlockScanInfo->delSkyline, &merge, pReader);
-      }
-
-      tRowMergerGetRow(&merge, &pTSRow);
-      doAppendRowFromTSRow(pReader->pResBlock, pReader, pTSRow, uid);
-      return TSDB_CODE_SUCCESS;
-    } else {  // key > ik.ts || key > k.ts
-      ASSERT(key != ik.ts);
-
-      // [3] ik.ts < key <= k.ts
-      // [4] ik.ts < k.ts <= key
-      if (ik.ts < k.ts) {
-        doMergeMemTableMultiRows(piRow, uid, &pBlockScanInfo->iiter, pDelList, &pTSRow, pReader, &freeTSRow);
-        doAppendRowFromTSRow(pReader->pResBlock, pReader, pTSRow, uid);
-        if (freeTSRow) {
-          taosMemoryFree(pTSRow);
-        }
-        return TSDB_CODE_SUCCESS;
-      }
-
-      // [5] k.ts < key   <= ik.ts
-      // [6] k.ts < ik.ts <= key
-      if (k.ts < ik.ts) {
-        doMergeMemTableMultiRows(pRow, uid, &pBlockScanInfo->iter, pDelList, &pTSRow, pReader, &freeTSRow);
-        doAppendRowFromTSRow(pReader->pResBlock, pReader, pTSRow, uid);
-        if (freeTSRow) {
-          taosMemoryFree(pTSRow);
-        }
-        return TSDB_CODE_SUCCESS;
-      }
-
-      // [7] k.ts == ik.ts < key
-      if (k.ts == ik.ts) {
-        ASSERT(key > ik.ts && key > k.ts);
-
-        doMergeMemIMemRows(pRow, piRow, pBlockScanInfo, pReader, &pTSRow);
-        doAppendRowFromTSRow(pReader->pResBlock, pReader, pTSRow, uid);
-        taosMemoryFree(pTSRow);
-        return TSDB_CODE_SUCCESS;
-      }
-    }
-  } else {  // descending order scan
-    // [1/2] k.ts >= ik.ts && k.ts >= key
-    if (k.ts >= ik.ts && k.ts >= key) {
-      STSchema* pSchema = doGetSchemaForTSRow(TSDBROW_SVERSION(pRow), pReader, pBlockScanInfo->uid);
-
-      tRowMergerInit(&merge, pRow, pSchema);
-      doMergeRowsInBuf(&pBlockScanInfo->iter, uid, key, pBlockScanInfo->delSkyline, &merge, pReader);
-
-      if (ik.ts == k.ts) {
-        tRowMerge(&merge, piRow);
-        doMergeRowsInBuf(&pBlockScanInfo->iiter, uid, key, pBlockScanInfo->delSkyline, &merge, pReader);
-      }
-
-      if (k.ts == key) {
-        TSDBROW fRow = tsdbRowFromBlockData(pBlockData, pDumpInfo->rowIndex);
-        tRowMerge(&merge, &fRow);
-        doMergeRowsInFileBlocks(pBlockData, pBlockScanInfo, pReader, &merge);
-      }
-
-      tRowMergerGetRow(&merge, &pTSRow);
-      doAppendRowFromTSRow(pReader->pResBlock, pReader, pTSRow, uid);
-      return TSDB_CODE_SUCCESS;
-    } else {
-      ASSERT(ik.ts != k.ts);  // this case has been included in the previous if branch
-
-      // [3] ik.ts > k.ts >= Key
-      // [4] ik.ts > key >= k.ts
-      if (ik.ts > key) {
-        doMergeMemTableMultiRows(piRow, uid, &pBlockScanInfo->iiter, pDelList, &pTSRow, pReader, &freeTSRow);
-        doAppendRowFromTSRow(pReader->pResBlock, pReader, pTSRow, uid);
-        if (freeTSRow) {
-          taosMemoryFree(pTSRow);
-        }
-        return TSDB_CODE_SUCCESS;
-      }
-
-      // [5] key > ik.ts > k.ts
-      // [6] key > k.ts > ik.ts
-      if (key > ik.ts) {
-        TSDBROW fRow = tsdbRowFromBlockData(pBlockData, pDumpInfo->rowIndex);
-        tRowMergerInit(&merge, &fRow, pReader->pSchema);
-
-        doMergeRowsInFileBlocks(pBlockData, pBlockScanInfo, pReader, &merge);
-        tRowMergerGetRow(&merge, &pTSRow);
-        doAppendRowFromTSRow(pReader->pResBlock, pReader, pTSRow, uid);
-        taosMemoryFree(pTSRow);
-        return TSDB_CODE_SUCCESS;
-      }
-
-      //[7] key = ik.ts > k.ts
-      if (key == ik.ts) {
-        doMergeMemTableMultiRows(piRow, uid, &pBlockScanInfo->iiter, pDelList, &pTSRow, pReader, &freeTSRow);
-
-        TSDBROW fRow = tsdbRowFromBlockData(pBlockData, pDumpInfo->rowIndex);
-        tRowMerge(&merge, &fRow);
-        doMergeRowsInFileBlocks(pBlockData, pBlockScanInfo, pReader, &merge);
-        tRowMergerGetRow(&merge, &pTSRow);
-        doAppendRowFromTSRow(pReader->pResBlock, pReader, pTSRow, uid);
-
-        taosMemoryFree(pTSRow);
-        return TSDB_CODE_SUCCESS;
-      }
-    }
-  }
-
-  ASSERT(0);
-  return -1;
-}
-#endif
-
 static int32_t initMemDataIterator(STableBlockScanInfo* pBlockScanInfo, STsdbReader* pReader) {
   if (pBlockScanInfo->iterInit) {
     return TSDB_CODE_SUCCESS;
@@ -2257,9 +2107,7 @@ static int32_t buildComposedDataBlock(STsdbReader* pReader) {
   SBlockData*         pBlockData = &pReader->status.fileBlockData;
   int32_t             step = ASCENDING_TRAVERSE(pReader->order) ? 1 : -1;
 
-
   while (1) {
-    // todo check the validate of row in file block
     bool hasBlockData = false;
     {
       while (pBlockData->nRow > 0) {  // find the first qualified row in data block
@@ -2620,7 +2468,7 @@ static int32_t doBuildDataBlock(STsdbReader* pReader) {
     code = buildComposedDataBlock(pReader);
   } else if (bufferDataInFileBlockGap(pReader->order, keyInBuf, pBlock)) {
     // data in memory that are earlier than current file block
-    // todo rows in buffer should be less than the file block in asc, greater than file block in desc
+    // rows in buffer should be less than the file block in asc, greater than file block in desc
     int64_t endKey = (ASCENDING_TRAVERSE(pReader->order)) ? pBlock->minKey.ts : pBlock->maxKey.ts;
     code = buildDataBlockFromBuf(pReader, pScanInfo, endKey);
   } else {