diff --git a/source/dnode/vnode/src/tsdb/tsdbRead.c b/source/dnode/vnode/src/tsdb/tsdbRead.c
index 558c3f6e59553829b982ee7d63d0fbdc66f89bdf..56797b61afd7d8165cd6a1afc8e0084c818969b8 100644
--- a/source/dnode/vnode/src/tsdb/tsdbRead.c
+++ b/source/dnode/vnode/src/tsdb/tsdbRead.c
@@ -22,12 +22,6 @@
                     .rows = (_block)->numOfRows,                                          \
                     .uid = (_checkInfo)->tableId})
 
-enum {
-  TSDB_CACHED_TYPE_NONE = 0,
-  TSDB_CACHED_TYPE_LASTROW = 1,
-  TSDB_CACHED_TYPE_LAST = 2,
-};
-
 typedef struct SQueryFilePos {
   int32_t     fid;
   int32_t     slot;
@@ -46,12 +40,6 @@ typedef struct SDataBlockLoadInfo {
   SArray*    pLoadedCols;
 } SDataBlockLoadInfo;
 
-enum {
-  CHECKINFO_CHOSEN_MEM = 0,
-  CHECKINFO_CHOSEN_IMEM = 1,
-  CHECKINFO_CHOSEN_BOTH = 2  // for update=2(merge case)
-};
-
 typedef struct STableBlockScanInfo {
   uint64_t     uid;
   TSKEY        lastKey;
@@ -74,10 +62,10 @@ typedef struct SBlockOrderWrapper {
 } SBlockOrderWrapper;
 
 typedef struct SBlockOrderSupporter {
-  int32_t           numOfTables;
   SBlockOrderWrapper**  pDataBlockInfo;
   int32_t*          indexPerTable;
   int32_t*          numOfBlocksPerTable;
+  int32_t           numOfTables;
 } SBlockOrderSupporter;
 
 typedef struct SIOCostSummary {
@@ -123,11 +111,6 @@ typedef struct SVersionRange {
   uint64_t maxVer;
 } SVersionRange;
 
-typedef struct SComposedDataBlock {
-  bool         composed;
-  int32_t      rows;
-} SComposedDataBlock;
-
 typedef struct SReaderStatus {
   SQueryFilePos      cur;             // current position
   bool               loadFromFile;    // check file stage
@@ -289,13 +272,10 @@ static SHashObj* createDataBlockScanInfo(STsdbReader* pTsdbReader, const STableK
 //   return pNew;
 // }
 
-static bool isEmptyQueryTimeWindow(STsdbReader* pTsdbReader) {
-   ASSERT(pTsdbReader != NULL);
-
-   STimeWindow* w = &pTsdbReader->window;
-   bool         asc = ASCENDING_TRAVERSE(pTsdbReader->order);
-
-   return ((asc && w->skey > w->ekey) || (!asc && w->ekey > w->skey));
+static bool isEmptyQueryTimeWindow(STimeWindow* pWindow, int32_t order) {
+   ASSERT(pWindow != NULL);
+   bool asc = ASCENDING_TRAVERSE(order);
+   return ((asc && pWindow->skey > pWindow->ekey) || (!asc && pWindow->ekey > pWindow->skey));
  }
 
 // // Update the query time window according to the data time to live(TTL) information, in order to avoid to return
@@ -334,34 +314,29 @@ static void setQueryTimewindow(STsdbReader* pReader, SQueryTableDataCond* pCond,
   // }
 }
 
-static void checkResultSize(const SQueryTableDataCond* pCond, STsdbReader* pReader) {
+static void limitOutputBufferSize(const SQueryTableDataCond* pCond, int32_t* capacity) {
   int32_t rowLen = 0;
   for (int32_t i = 0; i < pCond->numOfCols; ++i) {
     rowLen += pCond->colList[i].bytes;
   }
 
   // make sure the output SSDataBlock size be less than 2MB.
-  int32_t TWOMB = 2 * 1024 * 1024;
-  if (pReader->capacity * rowLen > TWOMB) {
-    pReader->capacity = TWOMB / rowLen;
+  const int32_t TWOMB = 2 * 1024 * 1024;
+  if ((*capacity) * rowLen > TWOMB) {
+    (*capacity) = TWOMB / rowLen;
   }
 }
 
 // init file iterator
-static int32_t initFileIterator(SFileSetIter* pIter, const STsdbFSState* pFState) {
+static int32_t initFileIterator(SFileSetIter* pIter, const STsdbFSState* pFState, const char* idstr) {
   pIter->index = -1;
   pIter->numOfFiles = taosArrayGetSize(pFState->aDFileSet);
   pIter->pFileList = taosArrayDup(pFState->aDFileSet);
 
+  tsdbDebug("init fileset iterator, total files:%d %s", pIter->numOfFiles, idstr);
   return TSDB_CODE_SUCCESS;
 }
 
-static void resetDataBlockIterator(SDataBlockIter* pIter) {
-  pIter->numOfBlocks = -1;
-  pIter->index = -1;
-  pIter->blockList = taosArrayInit(4, sizeof(SFileDataBlockInfo));
-}
-
 static bool filesetIteratorNext(SFileSetIter* pIter, int32_t order, STsdbReader* pReader) {
   pIter->index += 1;
   if (pIter->index >= pIter->numOfFiles) {
@@ -394,6 +369,12 @@ static bool filesetIteratorNext(SFileSetIter* pIter, int32_t order, STsdbReader*
   return false;
 }
 
+static void resetDataBlockIterator(SDataBlockIter* pIter) {
+  pIter->index = -1;
+  pIter->numOfBlocks = -1;
+  pIter->blockList = taosArrayInit(4, sizeof(SFileDataBlockInfo));
+}
+
 static void initReaderStatus(SReaderStatus* pStatus) {
   pStatus->cur.fid        = INT32_MIN;
   pStatus->cur.win        = TSWINDOW_INITIALIZER;
@@ -427,7 +408,7 @@ static int32_t tsdbReaderCreate(SVnode* pVnode, SQueryTableDataCond* pCond, STsd
   setQueryTimewindow(pReader, pCond, 0);
 
   if (pCond->numOfCols > 0) {
-    checkResultSize(pCond, pReader);
+    limitOutputBufferSize(pCond, &pReader->capacity);
 
     // allocate buffer in order to load data blocks from file
     pReader->suppInfo.pstatis = taosMemoryCalloc(pCond->numOfCols, sizeof(SColumnDataAgg));
@@ -450,7 +431,7 @@ static int32_t tsdbReaderCreate(SVnode* pVnode, SQueryTableDataCond* pCond, STsd
   }
 
   STsdbFSState* pFState = pReader->pTsdb->fs->cState;
-  initFileIterator(&pReader->status.fileIter, pFState);
+  initFileIterator(&pReader->status.fileIter, pFState, pReader->idStr);
   resetDataBlockIterator(&pReader->status.blockIter);
 
   // no data in files, let's try buffer in memory
@@ -520,93 +501,6 @@ _end:
 //   return res;
 // }
 
-// static bool initTableMemIterator(STsdbReader* pHandle, STableBlockScanInfo* pCheckInfo) {
-//   if (pCheckInfo->initBuf) {
-//     return true;
-//   }
-
-//   pCheckInfo->initBuf = true;
-//   int32_t order = pHandle->order;
-
-//   STbData* pMem = NULL;
-//   STbData* pIMem = NULL;
-//   int8_t   backward = (pHandle->order == TSDB_ORDER_DESC) ? 1 : 0;
-
-//   TSKEY tLastKey = keyToTkey(pCheckInfo->lastKey);
-//   if (pHandle->pTsdb->mem != NULL) {
-//     tsdbGetTbDataFromMemTable(pHandle->pTsdb->mem, pCheckInfo->suid, pCheckInfo->tableId, &pMem);
-//     if (pMem != NULL) {
-//       tsdbTbDataIterCreate(pMem, &(TSDBKEY){.version = 0, .ts = tLastKey}, backward, &pCheckInfo->iter);
-//     }
-//   }
-
-//   if (pHandle->pTsdb->imem != NULL) {
-//     tsdbGetTbDataFromMemTable(pHandle->pTsdb->mem, pCheckInfo->suid, pCheckInfo->tableId, &pIMem);
-//     if (pIMem != NULL) {
-//       tsdbTbDataIterCreate(pIMem, &(TSDBKEY){.version = 0, .ts = tLastKey}, backward, &pCheckInfo->iiter);
-//     }
-//   }
-
-//   // both iterators are NULL, no data in buffer right now
-//   if (pCheckInfo->iter == NULL && pCheckInfo->iiter == NULL) {
-//     return false;
-//   }
-
-//   bool memEmpty =
-//       (pCheckInfo->iter == NULL) || (pCheckInfo->iter != NULL && !tsdbTbDataIterGet(pCheckInfo->iter, NULL));
-//   bool imemEmpty =
-//       (pCheckInfo->iiter == NULL) || (pCheckInfo->iiter != NULL && !tsdbTbDataIterGet(pCheckInfo->iiter, NULL));
-//   if (memEmpty && imemEmpty) {  // buffer is empty
-//     return false;
-//   }
-
-//   if (!memEmpty) {
-//     TSDBROW row;
-
-//     tsdbTbDataIterGet(pCheckInfo->iter, &row);
-//     TSKEY key = row.pTSRow->ts;  // first timestamp in buffer
-//     tsdbDebug("%p uid:%" PRId64 ", check data in mem from skey:%" PRId64 ", order:%d, ts range in buf:%" PRId64
-//               "-%" PRId64 ", lastKey:%" PRId64 ", numOfRows:%" PRId64 ", %s",
-//               pHandle, pCheckInfo->tableId, key, order, pMem->minKey.ts, pMem->maxKey.ts, pCheckInfo->lastKey,
-//               pMem->sl.size, pHandle->idStr);
-
-//     if (ASCENDING_TRAVERSE(order)) {
-//       assert(pCheckInfo->lastKey <= key);
-//     } else {
-//       assert(pCheckInfo->lastKey >= key);
-//     }
-
-//   } else {
-//     tsdbDebug("%p uid:%" PRId64 ", no data in mem, %s", pHandle, pCheckInfo->tableId, pHandle->idStr);
-//   }
-
-//   if (!imemEmpty) {
-//     TSDBROW row;
-
-//     tsdbTbDataIterGet(pCheckInfo->iter, &row);
-//     TSKEY key = row.pTSRow->ts;  // first timestamp in buffer
-//     tsdbDebug("%p uid:%" PRId64 ", check data in imem from skey:%" PRId64 ", order:%d, ts range in buf:%" PRId64
-//               "-%" PRId64 ", lastKey:%" PRId64 ", numOfRows:%" PRId64 ", %s",
-//               pHandle, pCheckInfo->tableId, key, order, pIMem->minKey.ts, pIMem->maxKey.ts, pCheckInfo->lastKey,
-//               pIMem->sl.size, pHandle->idStr);
-
-//     if (ASCENDING_TRAVERSE(order)) {
-//       assert(pCheckInfo->lastKey <= key);
-//     } else {
-//       assert(pCheckInfo->lastKey >= key);
-//     }
-//   } else {
-//     tsdbDebug("%p uid:%" PRId64 ", no data in imem, %s", pHandle, pCheckInfo->tableId, pHandle->idStr);
-//   }
-
-//   return true;
-// }
-
-// static void destroyTableMemIterator(STableBlockScanInfo* pCheckInfo) {
-//   tsdbTbDataIterDestroy(pCheckInfo->iter);
-//   tsdbTbDataIterDestroy(pCheckInfo->iiter);
-// }
-
 // static TSKEY extractFirstTraverseKey(STableBlockScanInfo* pCheckInfo, int32_t order, int32_t update, TDRowVerT maxVer) {
 //   TSDBROW row = {0};
 //   STSRow *rmem = NULL, *rimem = NULL;
@@ -958,77 +852,79 @@ static int32_t doLoadFileBlock(STsdbReader* pReader, SArray* pIndexList, uint32_
   return TSDB_CODE_SUCCESS;
 }
 
-static void setBlockDumpCompleted(SFileBlockDumpInfo* pDumpInfo, SBlockData* pBlockData) {
-  pDumpInfo->rowIndex  = pBlockData->nRow;
-  pDumpInfo->totalRows = pBlockData->nRow;
-  pDumpInfo->lastKey   = pBlockData->aTSKEY[pBlockData->nRow - 1] + 1; // todo step value
+static void setBlockDumpCompleted(SFileBlockDumpInfo* pDumpInfo, SBlock* pBlock, int32_t order) {
+  int32_t step = ASCENDING_TRAVERSE(order)? 1:-1;
+
+  pDumpInfo->rowIndex  = pBlock->nRow;
+  pDumpInfo->totalRows = pBlock->nRow;
+  pDumpInfo->lastKey   = pBlock->maxKey.ts + step;
+}
+
+static void doCopyColVal(SColumnInfoData* pColInfoData, int32_t rowIndex, int32_t colIndex, SColVal* pColVal, SBlockLoadSuppInfo* pSup) {
+  if (IS_VAR_DATA_TYPE(pColVal->type)) {
+    if (pColVal->isNull) {
+      colDataAppendNULL(pColInfoData, rowIndex);
+    } else {
+      varDataSetLen(pSup->buildBuf[colIndex], pColVal->value.nData);
+      memcpy(varDataVal(pSup->buildBuf[colIndex]), pColVal->value.pData, pColVal->value.nData);
+      colDataAppend(pColInfoData, rowIndex, pSup->buildBuf[colIndex], false);
+    }
+  } else {
+    colDataAppend(pColInfoData, rowIndex, (const char*)&pColVal->value, pColVal->isNull);
+  }
 }
 
 static int32_t doLoadFileBlockData(STsdbReader* pReader, SDataBlockIter* pBlockIter, STableBlockScanInfo* pBlockScanInfo, SBlockData* pBlockData) {
- int64_t st = taosGetTimestampUs();
+  int64_t st = taosGetTimestampUs();
 
   SFileDataBlockInfo* pFBlock = getCurrentBlockInfo(pBlockIter);
-  SBlock* pBlock = taosArrayGet(pBlockScanInfo->pBlockList, pFBlock->tbBlockIdx);
-
- uint8_t *pb = NULL, *pb1 = NULL;
- int32_t code = tsdbReadBlockData(pReader->pFileReader, &pBlockScanInfo->blockIdx, pBlock, pBlockData, &pb, &pb1);
- if (code != TSDB_CODE_SUCCESS) {
-   goto _error;
- }
-
- for(int32_t i = 0; i < taosArrayGetSize(pReader->pResBlock->pDataBlock); ++i) {
-   SColumnInfoData* pColData = taosArrayGet(pReader->pResBlock->pDataBlock, i);
-   if (pColData->info.colId == PRIMARYKEY_TIMESTAMP_COL_ID) {
-     for (int32_t j = 0; j < pBlockData->nRow; ++j) {
-       colDataAppend(pColData, j, (const char*)&pBlockData->aTSKEY[j], false);
-     }
-   } else {
-     SColVal cv = {0};
-     SColData* pData = (SColData*)taosArrayGetP(pBlockData->aColDataP, pReader->suppInfo.slotIds[i] - 1);
-     for (int32_t j = 0; j < pBlockData->nRow; ++j) {
-       tColDataGetValue(pData, j, &cv);
-       colDataAppend(pColData, j, (const char*)&cv.value, cv.isNull);
-     }
-   }
- }
+  SBlock*             pBlock = taosArrayGet(pBlockScanInfo->pBlockList, pFBlock->tbBlockIdx);
+  SSDataBlock*        pResBlock = pReader->pResBlock;
 
- pReader->pResBlock->info.rows = pBlockData->nRow;
- setBlockDumpCompleted(&pReader->status.fBlockDumpInfo, pBlockData);
-
-/*
- int32_t ret = tsdbLoadBlockDataCols(&(pReader->rhelper), pBlock, pCheckInfo->pCompInfo, colIds,
-                                     (int)(QH_GET_NUM_OF_COLS(pReader)), true);
- if (ret != TSDB_CODE_SUCCESS) {
-   int32_t c = terrno;
-   assert(c != TSDB_CODE_SUCCESS);
-   goto _error;
- }
+  SBlockLoadSuppInfo* pSupInfo = &pReader->suppInfo;
 
- SDataBlockLoadInfo* pBlockLoadInfo = &pReader->dataBlockLoadInfo;
+  uint8_t *pb = NULL, *pb1 = NULL;
+  int32_t  code = tsdbReadBlockData(pReader->pFileReader, &pBlockScanInfo->blockIdx, pBlock, pBlockData, &pb, &pb1);
+  if (code != TSDB_CODE_SUCCESS) {
+    goto _error;
+  }
 
- pBlockLoadInfo->fileGroup = pReader->pFileGroup;
- pBlockLoadInfo->slot = pReader->cur.slot;
- pBlockLoadInfo->uid = pCheckInfo->tableId;
+  int32_t numOfCols = blockDataGetNumOfCols(pResBlock);
 
- SDataCols* pCols = pReader->rhelper.pDCols[0];
- assert(pCols->numOfRows != 0 && pCols->numOfRows <= pBlock->numOfRows);
+  SColVal cv = {0};
+  for (int32_t i = 0; i < numOfCols; ++i) {
+    SColumnInfoData* pColData = taosArrayGet(pResBlock->pDataBlock, i);
+    if (pColData->info.colId == PRIMARYKEY_TIMESTAMP_COL_ID) {
+      for (int32_t j = 0; j < pBlockData->nRow; ++j) {
+        colDataAppend(pColData, j, (const char*)&pBlockData->aTSKEY[j], false);
+      }
+    } else {
+      SColData* pData = (SColData*)taosArrayGetP(pBlockData->aColDataP, pSupInfo->slotIds[i] - 1);
+      for (int32_t j = 0; j < pBlockData->nRow; ++j) {
+        tColDataGetValue(pData, j, &cv);
+        doCopyColVal(pColData, j, i, &cv, pSupInfo);
+      }
+    }
+  }
 
- pBlock->numOfRows = pCols->numOfRows;
-*/
+  pResBlock->info.rows = pBlockData->nRow;
+  setBlockDumpCompleted(&pReader->status.fBlockDumpInfo, pBlock, pReader->order);
 
- int64_t elapsedTime = (taosGetTimestampUs() - st);
- pReader->cost.blockLoadTime += elapsedTime;
+  int64_t elapsedTime = (taosGetTimestampUs() - st);
+  pReader->cost.blockLoadTime += elapsedTime;
 
- tsdbDebug("%p load file block into buffer, global index:%d, table index:%d, brange:%" PRId64 "-%" PRId64
-           ", rows:%d, minVer:%" PRId64 ", maxVer:%" PRId64 ", elapsed time:%" PRId64 " us, %s",
-           pReader, pBlockIter->index, pFBlock->tbBlockIdx, pBlock->minKey.ts, pBlock->maxKey.ts, pBlockData->nRow,
-           pBlock->minVersion, pBlock->maxVersion, elapsedTime, pReader->idStr);
- return TSDB_CODE_SUCCESS;
+  tsdbDebug("%p load file block into buffer, global index:%d, table index:%d, brange:%" PRId64 "-%" PRId64
+            ", rows:%d, minVer:%" PRId64 ", maxVer:%" PRId64 ", elapsed time:%" PRId64 " us, %s",
+            pReader, pBlockIter->index, pFBlock->tbBlockIdx, pBlock->minKey.ts, pBlock->maxKey.ts, pBlockData->nRow,
+            pBlock->minVersion, pBlock->maxVersion, elapsedTime, pReader->idStr);
+  return TSDB_CODE_SUCCESS;
 
 _error:
- tsdbError("%p error occurs in loading file block, global index:%d, table index:%d, brange:%" PRId64 "-%" PRId64 ", rows:%d, %s",
-           pReader, pBlockIter->index, pFBlock->tbBlockIdx, pBlock->minKey.ts, pBlock->maxKey.ts, pBlock->nRow, pReader->idStr);
- return code;
+  tsdbError("%p error occurs in loading file block, global index:%d, table index:%d, brange:%" PRId64 "-%" PRId64
+            ", rows:%d, %s",
+            pReader, pBlockIter->index, pFBlock->tbBlockIdx, pBlock->minKey.ts, pBlock->maxKey.ts, pBlock->nRow,
+            pReader->idStr);
+  return code;
 }
 
 // static int32_t handleDataMergeIfNeeded(STsdbReader* pTsdbReadHandle, SBlock* pBlock, STableBlockScanInfo* pCheckInfo) {
@@ -2492,9 +2388,18 @@ static int32_t initMemIterator(STableBlockScanInfo* pBlockScanInfo, STsdbReader*
     if (d != NULL) {
       code = tsdbTbDataIterCreate(d, &startKey, 0, &pBlockScanInfo->iter);
       if (code != TSDB_CODE_SUCCESS) {
+        tsdbError("%p uid:%" PRId64 ", failed to create iterator for imem, code:%s, %s",
+                  pReader, pBlockScanInfo->uid, tstrerror(code), pReader->idStr);
         return code;
+      } else {
+        tsdbDebug("%p uid:%" PRId64 ", check data in mem from skey:%" PRId64 ", order:%d, ts range in buf:%" PRId64
+                  "-%" PRId64 " %s",
+                  pReader, pBlockScanInfo->uid, pReader->window.skey, pReader->order, d->minKey, d->maxKey,
+                  pReader->idStr);
       }
     }
+  } else {
+     tsdbDebug("%p uid:%" PRId64 ", no data in mem, %s", pReader, pBlockScanInfo->uid, pReader->idStr);
   }
 
   STbData* di = NULL;
@@ -2503,9 +2408,18 @@ static int32_t initMemIterator(STableBlockScanInfo* pBlockScanInfo, STsdbReader*
     if (di != NULL) {
       code = tsdbTbDataIterCreate(di, &startKey, 0, &pBlockScanInfo->iiter);
       if (code != TSDB_CODE_SUCCESS) {
+        tsdbError("%p uid:%" PRId64 ", failed to create iterator for mem, code:%s, %s",
+                  pReader, pBlockScanInfo->uid, tstrerror(code), pReader->idStr);
         return code;
+      } else {
+        tsdbDebug("%p uid:%" PRId64 ", check data in imem from skey:%" PRId64 ", order:%d, ts range in buf:%" PRId64
+                      "-%" PRId64 " %s",
+                  pReader, pBlockScanInfo->uid, pReader->window.skey, pReader->order, di->minKey, di->maxKey,
+                  pReader->idStr);
       }
     }
+  } else {
+    tsdbDebug("%p uid:%" PRId64 ", no data in imem, %s", pReader, pBlockScanInfo->uid, pReader->idStr);
   }
 
   pBlockScanInfo->iterInit = true;
@@ -2605,24 +2519,24 @@ static int32_t doBuildDataBlock(STsdbReader* pReader) {
     // 2. current block should not overlap with next neighbor block
     // 3. current timestamp should not be overlap with each other
     SDataBlockInfo* pInfo = &pReader->pResBlock->info;
-    pInfo->rows = pBlock->nRow;
-    pInfo->uid  = pScanInfo->uid;
-    pInfo->window.skey = pBlock->minKey.ts;
-    pInfo->window.ekey = pBlock->maxKey.ts;
+    pInfo->rows   = pBlock->nRow;
+    pInfo->uid    = pScanInfo->uid;
+    pInfo->window = (STimeWindow) {.skey = pBlock->minKey.ts, .ekey = pBlock->maxKey.ts};
     setComposedBlockFlag(pReader, false);
+    setBlockDumpCompleted(&pStatus->fBlockDumpInfo, pBlock, pReader->order);
   }
 
   return code;
 }
 
-static int32_t buildBlockFromBufferSeqentially(STsdbReader* pReader) {
+static int32_t buildBlockFromBufferSequentially(STsdbReader* pReader) {
   SReaderStatus* pStatus = &pReader->status;
 
   while(1) {
     if (pStatus->pTableIter == NULL) {
       pStatus->pTableIter = taosHashIterate(pStatus->pTableMap, NULL);
       if (pStatus->pTableIter == NULL) {
-        return false;
+        return TSDB_CODE_SUCCESS;
       }
     }
 
@@ -2630,20 +2544,26 @@ static int32_t buildBlockFromBufferSeqentially(STsdbReader* pReader) {
     initMemIterator(pBlockScanInfo, pReader);
 
     TSDBKEY maxKey = {.ts = pReader->window.ekey, .version = pReader->verRange.maxVer};
-    buildInmemDataBlock(pReader, pBlockScanInfo, &maxKey);
+    int32_t code = buildInmemDataBlock(pReader, pBlockScanInfo, &maxKey);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
     if (pReader->pResBlock->info.rows > 0) {
-      return true;
+      return TSDB_CODE_SUCCESS;
     }
 
     // current table is exhausted, let's try the next table
     pStatus->pTableIter = taosHashIterate(pStatus->pTableMap, pStatus->pTableIter);
     if (pStatus->pTableIter == NULL) {
-      return false;
+      return TSDB_CODE_SUCCESS;
     }
   }
 }
 
 static int32_t buildBlockFromFiles(STsdbReader* pReader) {
+  int32_t code = TSDB_CODE_SUCCESS;
+
   SReaderStatus* pStatus = &pReader->status;
   SFileSetIter*  pFIter = &pStatus->fileIter;
 
@@ -2652,7 +2572,7 @@ static int32_t buildBlockFromFiles(STsdbReader* pReader) {
   if (pFIter->index < pFIter->numOfFiles) {
     if (pReader->status.blockIter.index == -1) {
       int32_t numOfBlocks = 0;
-      int32_t code = moveToNextFile(pReader, &numOfBlocks);
+      code = moveToNextFile(pReader, &numOfBlocks);
       if (code != TSDB_CODE_SUCCESS) {
         return code;
       }
@@ -2664,7 +2584,9 @@ static int32_t buildBlockFromFiles(STsdbReader* pReader) {
       }
 
       code = doBuildDataBlock(pReader);
-
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
     } else {
       SFileBlockDumpInfo* pDumpInfo = &pReader->status.fBlockDumpInfo;
       SFileDataBlockInfo* pFBlock = getCurrentBlockInfo(&pReader->status.blockIter);
@@ -2676,7 +2598,7 @@ static int32_t buildBlockFromFiles(STsdbReader* pReader) {
         bool hasNext = blockIteratorNext(&pReader->status.blockIter);
         if (!hasNext) { // current file is exhausted, let's try the next file
           int32_t numOfBlocks = 0;
-          int32_t code = moveToNextFile(pReader, &numOfBlocks);
+          code = moveToNextFile(pReader, &numOfBlocks);
           if (code != TSDB_CODE_SUCCESS) {
             return code;
           }
@@ -2692,15 +2614,21 @@ static int32_t buildBlockFromFiles(STsdbReader* pReader) {
               return code;
             }
 
-            doBuildDataBlock(pReader);
+            code = doBuildDataBlock(pReader);
+            if (code != TSDB_CODE_SUCCESS) {
+              return code;
+            }
           }
         } else { // try next data block in current file
           blockIteratorNext(pBlockIter);
-          doBuildDataBlock(pReader);
+          code = doBuildDataBlock(pReader);
+          if (code != TSDB_CODE_SUCCESS) {
+            return code;
+          }
         }
       } else {
-        buildComposedDataBlock(pReader, pFBlock, pBlock, pScanInfo);
-        return TSDB_CODE_SUCCESS;
+        code = buildComposedDataBlock(pReader, pFBlock, pBlock, pScanInfo);
+        return code;
       }
 
       // repeat the previous procedure.
@@ -2708,7 +2636,7 @@ static int32_t buildBlockFromFiles(STsdbReader* pReader) {
     }
   }
 
-  return TSDB_CODE_SUCCESS;
+  return code;
 }
 
 // // todo not unref yet, since it is not support multi-group interpolation query
@@ -2901,18 +2829,7 @@ int32_t doAppendOneRow(SSDataBlock* pBlock, STsdbReader* pReader, STSRow* pTSRow
       colDataAppend(pColInfoData, numOfRows, (const char*) &pTSRow->ts, false);
     } else {
       tTSRowGetVal(pTSRow, pReader->pSchema, slotId, &colVal);
-
-      if (IS_VAR_DATA_TYPE(colVal.type)) {
-        if (colVal.isNull) {
-          colDataAppendNULL(pColInfoData, numOfRows);
-        } else {
-          varDataSetLen(pSupInfo->buildBuf[i], colVal.value.nData);
-          memcpy(varDataVal(pSupInfo->buildBuf[i]), colVal.value.pData, colVal.value.nData);
-          colDataAppend(pColInfoData, numOfRows, pSupInfo->buildBuf[i], false);
-        }
-      } else {
-        colDataAppend(pColInfoData, numOfRows, (const char*)&colVal.value, colVal.isNull);
-      }
+      doCopyColVal(pColInfoData, i, numOfRows, &colVal, pSupInfo);
     }
   }
 
@@ -3198,7 +3115,7 @@ int32_t tsdbReaderOpen(SVnode* pVnode, SQueryTableDataCond* pCond, SArray* pTabl
   }
 
   STsdbReader* pReader = *ppReader;
-  if (isEmptyQueryTimeWindow(pReader)) {
+  if (isEmptyQueryTimeWindow(&pReader->window, pReader->order)) {
     tsdbDebug("%p query window not overlaps with the data set, no result returned, %s", pReader, pReader->idStr);
     return TSDB_CODE_SUCCESS;
   }
@@ -3259,7 +3176,7 @@ void tsdbReaderClose(STsdbReader* pReader) {
    taosMemoryFreeClear(pReader->suppInfo.plist);
    taosMemoryFree(pReader->suppInfo.slotIds);
 
-   if (!isEmptyQueryTimeWindow(pReader)) {
+   if (!isEmptyQueryTimeWindow(&pReader->window, pReader->order)) {
      //    tsdbMayUnTakeMemSnapshot(pTsdbReadHandle);
    } else {
      ASSERT(pReader->status.pTableMap == NULL);
@@ -3291,7 +3208,7 @@ void tsdbReaderClose(STsdbReader* pReader) {
 }
 
 bool tsdbNextDataBlock(STsdbReader* pReader) {
-  if (isEmptyQueryTimeWindow(pReader)) {
+  if (isEmptyQueryTimeWindow(&pReader->window, pReader->order)) {
     return false;
   }
 
@@ -3313,11 +3230,11 @@ bool tsdbNextDataBlock(STsdbReader* pReader) {
       if (pBlock->info.rows > 0) {
         return true;
       } else {
-        buildBlockFromBufferSeqentially(pReader);
+        buildBlockFromBufferSequentially(pReader);
         return pBlock->info.rows > 0;
       }
     } else { // no data in files, let's try the buffer
-      buildBlockFromBufferSeqentially(pReader);
+      buildBlockFromBufferSequentially(pReader);
       return pBlock->info.rows > 0;
     }
   } else if (pReader->type == BLOCK_LOAD_TABLESEQ_ORDER) {
@@ -3370,13 +3287,12 @@ void tsdbRetrieveDataBlockInfo(STsdbReader* pReader, SDataBlockInfo* pDataBlockI
 
 int32_t tsdbRetrieveDataBlockStatisInfo(STsdbReader* pReader, SColumnDataAgg*** pBlockStatis, bool* allHave) {
   int32_t code = 0;
-  // *allHave = false;
+   *allHave = false;
 
-  // SQueryFilePos* c = &pReader->cur;
-  // if (c->mixBlock) {
-  //   *pBlockStatis = NULL;
-  //   return TSDB_CODE_SUCCESS;
-  // }
+   if (pReader->status.composedDataBlock) {
+     *pBlockStatis = NULL;
+     return TSDB_CODE_SUCCESS;
+   }
 
   // SFileBlockInfo* pBlockInfo = &pReader->pDataBlockInfo[c->slot];
   // assert((c->slot >= 0 && c->slot < pReader->numOfBlocks) || ((c->slot == pReader->numOfBlocks) && (c->slot == 0)));