diff --git a/src/common/inc/tdataformat.h b/src/common/inc/tdataformat.h
index cb39b990e53fe54ffe20a1136a8a12d2f2d86875..3a84ce8f6f3ad369e9f6972d79d3356451c4ef25 100644
--- a/src/common/inc/tdataformat.h
+++ b/src/common/inc/tdataformat.h
@@ -251,7 +251,7 @@ void       tdFreeDataCols(SDataCols *pCols);
 void       tdAppendDataRowToDataCol(SDataRow row, STSchema *pSchema, SDataCols *pCols);
 void       tdPopDataColsPoints(SDataCols *pCols, int pointsToPop);  //!!!!
 int        tdMergeDataCols(SDataCols *target, SDataCols *src, int rowsToMerge);
-void       tdMergeTwoDataCols(SDataCols *target, SDataCols *src1, int *iter1, SDataCols *src2, int *iter2, int tRows);
+void       tdMergeTwoDataCols(SDataCols *target, SDataCols *src1, int *iter1, int limit1, SDataCols *src2, int *iter2, int limit2, int tRows);
 
 // ----------------- K-V data row structure
 /*
diff --git a/src/common/src/tdataformat.c b/src/common/src/tdataformat.c
index 5cd3b79aa1d1d5b088473cd8cdc3f8a0ec801ec5..7880a4b3021d71872f194f7bd5512d03ee940363 100644
--- a/src/common/src/tdataformat.c
+++ b/src/common/src/tdataformat.c
@@ -450,7 +450,8 @@ int tdMergeDataCols(SDataCols *target, SDataCols *source, int rowsToMerge) {
 
     int iter1 = 0;
     int iter2 = 0;
-    tdMergeTwoDataCols(target, pTarget, &iter1, source, &iter2, pTarget->numOfRows + rowsToMerge);
+    tdMergeTwoDataCols(target, pTarget, &iter1, pTarget->numOfRows, source, &iter2, source->numOfRows,
+                       pTarget->numOfRows + rowsToMerge);
   }
 
   tdFreeDataCols(pTarget);
@@ -461,15 +462,15 @@ _err:
   return -1;
 }
 
-void tdMergeTwoDataCols(SDataCols *target, SDataCols *src1, int *iter1, SDataCols *src2, int *iter2, int tRows) {
-  // TODO: add resolve duplicate key here
+void tdMergeTwoDataCols(SDataCols *target, SDataCols *src1, int *iter1, int limit1, SDataCols *src2, int *iter2, int limit2, int tRows) {
   tdResetDataCols(target);
+  ASSERT(limit1 <= src1->numOfRows && limit2 <= src2->numOfRows);
 
   while (target->numOfRows < tRows) {
-    if (*iter1 >= src1->numOfRows && *iter2 >= src2->numOfRows) break;
+    if (*iter1 >= limit1 && *iter2 >= limit2) break;
 
-    TSKEY key1 = (*iter1 >= src1->numOfRows) ? INT64_MAX : ((TSKEY *)(src1->cols[0].pData))[*iter1];
-    TSKEY key2 = (*iter2 >= src2->numOfRows) ? INT64_MAX : ((TSKEY *)(src2->cols[0].pData))[*iter2];
+    TSKEY key1 = (*iter1 >= limit1) ? INT64_MAX : ((TSKEY *)(src1->cols[0].pData))[*iter1];
+    TSKEY key2 = (*iter2 >= limit2) ? INT64_MAX : ((TSKEY *)(src2->cols[0].pData))[*iter2];
 
     if (key1 <= key2) {
       for (int i = 0; i < src1->numOfCols; i++) {
diff --git a/src/tsdb/src/tsdbRWHelper.c b/src/tsdb/src/tsdbRWHelper.c
index fd317e9d0cebf016652952d9eb370d5fbad95143..eab70b591349cacfc382c206e393a4846283a559 100644
--- a/src/tsdb/src/tsdbRWHelper.c
+++ b/src/tsdb/src/tsdbRWHelper.c
@@ -977,7 +977,8 @@ static int tsdbMergeDataWithBlock(SRWHelper *pHelper, int blkIdx, SDataCols *pDa
       // tdResetDataCols(pHelper->pDataCols[1]);
       while (true) {
         if (iter1 >= pHelper->pDataCols[0]->numOfRows && iter2 >= rows3) break;
-        tdMergeTwoDataCols(pHelper->pDataCols[1], pHelper->pDataCols[0], &iter1, pDataCols, &iter2, pHelper->config.maxRowsPerFileBlock * 4 / 5);
+        tdMergeTwoDataCols(pHelper->pDataCols[1], pHelper->pDataCols[0], &iter1, pHelper->pDataCols[0]->numOfRows,
+                           pDataCols, &iter2, rowsWritten, pHelper->config.maxRowsPerFileBlock * 4 / 5);
         ASSERT(pHelper->pDataCols[1]->numOfRows > 0);
         if (tsdbWriteBlockToFile(pHelper, &(pHelper->files.dataF), pHelper->pDataCols[1],
                                  pHelper->pDataCols[1]->numOfRows, &compBlock, false, true) < 0)
@@ -989,54 +990,6 @@ static int tsdbMergeDataWithBlock(SRWHelper *pHelper, int blkIdx, SDataCols *pDa
         }
         round++;
         blkIdx++;
-        // TODO: the blkIdx here is not correct
-
-        // if (iter1 >= pHelper->pDataCols[0]->numOfRows && iter2 >= rows3) {
-        //   if (pHelper->pDataCols[1]->numOfRows > 0) {
-        //     if (tsdbWriteBlockToFile(pHelper, &pHelper->files.dataF, pHelper->pDataCols[1],
-        //                              pHelper->pDataCols[1]->numOfRows, &compBlock, false, true) < 0)
-        //       goto _err;
-        //     // TODO: the blkIdx here is not correct
-        //     tsdbAddSubBlock(pHelper, &compBlock, blkIdx, pHelper->pDataCols[1]->numOfRows);
-        //   }
-        // }
-
-        // TSKEY key1 = iter1 >= pHelper->pDataCols[0]->numOfRows
-        //                  ? INT64_MAX
-        //                  : ((int64_t *)(pHelper->pDataCols[0]->cols[0].pData))[iter1];
-        // TSKEY key2 = iter2 >= rowsWritten ? INT64_MAX : ((int64_t *)(pDataCols->cols[0].pData))[iter2];
-
-        // if (key1 < key2) {
-        //   for (int i = 0; i < pDataCols->numOfCols; i++) {
-        //     SDataCol *pDataCol = pHelper->pDataCols[1]->cols + i;
-        //     memcpy(((char *)pDataCol->pData + TYPE_BYTES[pDataCol->type] * pHelper->pDataCols[1]->numOfRows),
-        //            ((char *)pHelper->pDataCols[0]->cols[i].pData + TYPE_BYTES[pDataCol->type] * iter1),
-        //            TYPE_BYTES[pDataCol->type]);
-        //   }
-        //   pHelper->pDataCols[1]->numOfRows++;
-        //   iter1++;
-        // } else if (key1 == key2) {
-        //   // TODO: think about duplicate key cases
-        //   ASSERT(false);
-        // } else {
-        //   for (int i = 0; i < pDataCols->numOfCols; i++) {
-        //     SDataCol *pDataCol = pHelper->pDataCols[1]->cols + i;
-        //     memcpy(((char *)pDataCol->pData + TYPE_BYTES[pDataCol->type] * pHelper->pDataCols[1]->numOfRows),
-        //            ((char *)pDataCols->cols[i].pData +
-        //             TYPE_BYTES[pDataCol->type] * iter2),
-        //            TYPE_BYTES[pDataCol->type]);
-        //   }
-        //   pHelper->pDataCols[1]->numOfRows++;
-        //   iter2++;
-        // }
-
-        // if (pHelper->pDataCols[0]->numOfRows >= pHelper->config.maxRowsPerFileBlock * 4 / 5) {
-        //   if (tsdbWriteBlockToFile(pHelper, &pHelper->files.dataF, pHelper->pDataCols[1], pHelper->pDataCols[1]->numOfRows, &compBlock, false, true) < 0) goto _err;
-        //   // TODO: blkIdx here is not correct, fix it
-        //   tsdbInsertSuperBlock(pHelper, &compBlock, blkIdx);
-
-        //   tdResetDataCols(pHelper->pDataCols[1]);
-        // }
       }
     }
   }