other: add files.

source/dnode/vnode/inc/vnode.h

@@ -161,6 +161,27 @@ uint64_t     tsdbGetReaderMaxVersion(STsdbReader *pReader);
 void         tsdbReaderSetCloseFlag(STsdbReader *pReader);
 int64_t      tsdbGetLastTimestamp(SVnode *pVnode, void *pTableList, int32_t numOfTables, const char *pIdStr);
 
+//======================================================================================================================
+int32_t      tsdbReaderOpen2(void *pVnode, SQueryTableDataCond *pCond, void *pTableList, int32_t numOfTables,
+                            SSDataBlock *pResBlock, void **ppReader, const char *idstr, bool countOnly,
+                            SHashObj **pIgnoreTables);
+int32_t      tsdbSetTableList2(STsdbReader *pReader, const void *pTableList, int32_t num);
+void         tsdbReaderSetId2(STsdbReader *pReader, const char *idstr);
+void         tsdbReaderClose2(STsdbReader *pReader);
+int32_t      tsdbNextDataBlock2(STsdbReader *pReader, bool *hasNext);
+int32_t      tsdbRetrieveDatablockSMA2(STsdbReader *pReader, SSDataBlock *pDataBlock, bool *allHave, bool *hasNullSMA);
+void         tsdbReleaseDataBlock2(STsdbReader *pReader);
+SSDataBlock *tsdbRetrieveDataBlock2(STsdbReader *pTsdbReadHandle, SArray *pColumnIdList);
+int32_t      tsdbReaderReset2(STsdbReader *pReader, SQueryTableDataCond *pCond);
+int32_t      tsdbGetFileBlocksDistInfo2(STsdbReader *pReader, STableBlockDistInfo *pTableBlockInfo);
+int64_t      tsdbGetNumOfRowsInMemTable2(STsdbReader *pHandle);
+void        *tsdbGetIdx2(SMeta *pMeta);
+void        *tsdbGetIvtIdx2(SMeta *pMeta);
+uint64_t     tsdbGetReaderMaxVersion2(STsdbReader *pReader);
+void         tsdbReaderSetCloseFlag2(STsdbReader *pReader);
+int64_t      tsdbGetLastTimestamp2(SVnode *pVnode, void *pTableList, int32_t numOfTables, const char *pIdStr);
+//======================================================================================================================
+
 int32_t tsdbReuseCacherowsReader(void *pReader, void *pTableIdList, int32_t numOfTables);
 int32_t tsdbCacherowsReaderOpen(void *pVnode, int32_t type, void *pTableIdList, int32_t numOfTables, int32_t numOfCols,
                                 SArray *pCidList, int32_t *pSlotIds, uint64_t suid, void **pReader, const char *idstr);

source/dnode/vnode/src/tsdb/tsdbRead2.c

+/*
+ * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
+ *
+ * This program is free software: you can use, redistribute, and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3
+ * or later ("AGPL"), as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "osDef.h"
+#include "tsdb.h"
+#include "tsimplehash.h"
+
+#define ASCENDING_TRAVERSE(o) (o == TSDB_ORDER_ASC)
+#define getCurrentKeyInLastBlock(_r) ((_r)->currentKey)
+
+typedef enum {
+  READER_STATUS_SUSPEND = 0x1,
+  READER_STATUS_NORMAL = 0x2,
+} EReaderStatus;
+
+typedef enum {
+  EXTERNAL_ROWS_PREV = 0x1,
+  EXTERNAL_ROWS_MAIN = 0x2,
+  EXTERNAL_ROWS_NEXT = 0x3,
+} EContentData;
+
+typedef enum {
+  READ_MODE_COUNT_ONLY = 0x1,
+  READ_MODE_ALL,
+} EReadMode;
+
+typedef struct {
+  STbDataIter* iter;
+  int32_t      index;
+  bool         hasVal;
+} SIterInfo;
+
+typedef struct {
+  int32_t numOfBlocks;
+  int32_t numOfLastFiles;
+} SBlockNumber;
+
+typedef struct SBlockIndex {
+  int32_t     ordinalIndex;
+  int64_t     inFileOffset;
+  STimeWindow window;  // todo replace it with overlap flag.
+} SBlockIndex;
+
+typedef struct STableBlockScanInfo {
+  uint64_t  uid;
+  TSKEY     lastKey;
+  TSKEY     lastKeyInStt;       // last accessed key in stt
+  SMapData  mapData;            // block info (compressed)
+  SArray*   pBlockList;         // block data index list, SArray<SBlockIndex>
+  SIterInfo iter;               // mem buffer skip list iterator
+  SIterInfo iiter;              // imem buffer skip list iterator
+  SArray*   delSkyline;         // delete info for this table
+  int32_t   fileDelIndex;       // file block delete index
+  int32_t   lastBlockDelIndex;  // delete index for last block
+  bool      iterInit;           // whether to initialize the in-memory skip list iterator or not
+} STableBlockScanInfo;
+
+typedef struct SBlockOrderWrapper {
+  int64_t uid;
+  int64_t offset;
+} SBlockOrderWrapper;
+
+typedef struct SBlockOrderSupporter {
+  SBlockOrderWrapper** pDataBlockInfo;
+  int32_t*             indexPerTable;
+  int32_t*             numOfBlocksPerTable;
+  int32_t              numOfTables;
+} SBlockOrderSupporter;
+
+typedef struct SIOCostSummary {
+  int64_t numOfBlocks;
+  double  blockLoadTime;
+  double  buildmemBlock;
+  int64_t headFileLoad;
+  double  headFileLoadTime;
+  int64_t smaDataLoad;
+  double  smaLoadTime;
+  int64_t lastBlockLoad;
+  double  lastBlockLoadTime;
+  int64_t composedBlocks;
+  double  buildComposedBlockTime;
+  double  createScanInfoList;
+  //  double  getTbFromMemTime;
+  //  double  getTbFromIMemTime;
+  double initDelSkylineIterTime;
+} SIOCostSummary;
+
+typedef struct SBlockLoadSuppInfo {
+  SArray*        pColAgg;
+  SColumnDataAgg tsColAgg;
+  int16_t*       colId;
+  int16_t*       slotId;
+  int32_t        numOfCols;
+  char**         buildBuf;  // build string tmp buffer, todo remove it later after all string format being updated.
+  bool           smaValid;  // the sma on all queried columns are activated
+} SBlockLoadSuppInfo;
+
+typedef struct SLastBlockReader {
+  STimeWindow        window;
+  SVersionRange      verRange;
+  int32_t            order;
+  uint64_t           uid;
+  SMergeTree         mergeTree;
+  SSttBlockLoadInfo* pInfo;
+  int64_t            currentKey;
+} SLastBlockReader;
+
+typedef struct SFilesetIter {
+  int32_t           numOfFiles;  // number of total files
+  int32_t           index;       // current accessed index in the list
+  SArray*           pFileList;   // data file list
+  int32_t           order;
+  SLastBlockReader* pLastBlockReader;  // last file block reader
+} SFilesetIter;
+
+typedef struct SFileDataBlockInfo {
+  // index position in STableBlockScanInfo in order to check whether neighbor block overlaps with it
+  uint64_t uid;
+  int32_t  tbBlockIdx;
+} SFileDataBlockInfo;
+
+typedef struct SDataBlockIter {
+  int32_t    numOfBlocks;
+  int32_t    index;
+  SArray*    blockList;  // SArray<SFileDataBlockInfo>
+  int32_t    order;
+  SDataBlk   block;  // current SDataBlk data
+  SSHashObj* pTableMap;
+} SDataBlockIter;
+
+typedef struct SFileBlockDumpInfo {
+  int32_t totalRows;
+  int32_t rowIndex;
+  int64_t lastKey;
+  bool    allDumped;
+} SFileBlockDumpInfo;
+
+typedef struct STableUidList {
+  uint64_t* tableUidList;  // access table uid list in uid ascending order list
+  int32_t   currentIndex;  // index in table uid list
+} STableUidList;
+
+typedef struct SReaderStatus {
+  bool                  loadFromFile;       // check file stage
+  bool                  composedDataBlock;  // the returned data block is a composed block or not
+  bool                  mapDataCleaned;     // mapData has been cleaned up alreay or not
+  SSHashObj*            pTableMap;          // SHash<STableBlockScanInfo>
+  STableBlockScanInfo** pTableIter;         // table iterator used in building in-memory buffer data blocks.
+  STableUidList         uidList;            // check tables in uid order, to avoid the repeatly load of blocks in STT.
+  SFileBlockDumpInfo    fBlockDumpInfo;
+  SDFileSet*            pCurrentFileset;  // current opened file set
+  SBlockData            fileBlockData;
+  SFilesetIter          fileIter;
+  SDataBlockIter        blockIter;
+  SLDataIter*           pLDataIter;
+  SRowMerger            merger;
+  SColumnInfoData*      pPrimaryTsCol;      // primary time stamp output col info data
+} SReaderStatus;
+
+typedef struct SBlockInfoBuf {
+  int32_t currentIndex;
+  SArray* pData;
+  int32_t numPerBucket;
+  int32_t numOfTables;
+} SBlockInfoBuf;
+
+typedef struct STsdbReaderAttr {
+  STSchema*     pSchema;
+  EReadMode     readMode;
+  uint64_t      rowsNum;
+  STimeWindow   window;
+  bool          freeBlock;
+  SVersionRange verRange;
+  int16_t       order;
+} STsdbReaderAttr;
+
+typedef struct SResultBlockInfo {
+  SSDataBlock* pResBlock;
+  bool         freeBlock;
+  int64_t      capacity;
+} SResultBlockInfo;
+
+struct STsdbReader {
+  STsdb*             pTsdb;
+  SVersionRange      verRange;
+  TdThreadMutex      readerMutex;
+  EReaderStatus      flag;
+  int32_t            code;
+  uint64_t           suid;
+  int16_t            order;
+  EReadMode          readMode;
+  uint64_t           rowsNum;
+  STimeWindow        window;  // the primary query time window that applies to all queries
+  SResultBlockInfo   resBlockInfo;
+  SReaderStatus      status;
+  char*              idStr;  // query info handle, for debug purpose
+  int32_t            type;   // query type: 1. retrieve all data blocks, 2. retrieve direct prev|next rows
+  SBlockLoadSuppInfo suppInfo;
+  STsdbReadSnap*     pReadSnap;
+  SIOCostSummary     cost;
+  SHashObj**         pIgnoreTables;
+  STSchema*          pSchema;      // the newest version schema
+  SSHashObj*         pSchemaMap;   // keep the retrieved schema info, to avoid the overhead by repeatly load schema
+  SDataFReader*      pFileReader;  // the file reader
+  SDelFReader*       pDelFReader;  // the del file reader
+  SArray*            pDelIdx;      // del file block index;
+  SBlockInfoBuf      blockInfoBuf;
+  EContentData       step;
+  STsdbReader*       innerReader[2];
+};
+
+static SFileDataBlockInfo* getCurrentBlockInfo(SDataBlockIter* pBlockIter);
+static int      buildDataBlockFromBufImpl(STableBlockScanInfo* pBlockScanInfo, int64_t endKey, int32_t capacity,
+                                          STsdbReader* pReader);
+static TSDBROW* getValidMemRow(SIterInfo* pIter, const SArray* pDelList, STsdbReader* pReader);
+static int32_t  doMergeRowsInFileBlocks(SBlockData* pBlockData, STableBlockScanInfo* pScanInfo, STsdbReader* pReader);
+static int32_t  doMergeRowsInLastBlock(SLastBlockReader* pLastBlockReader, STableBlockScanInfo* pScanInfo, int64_t ts,
+                                       SRowMerger* pMerger, SVersionRange* pVerRange, const char* id);
+static int32_t  doMergeRowsInBuf(SIterInfo* pIter, uint64_t uid, int64_t ts, SArray* pDelList, STsdbReader* pReader);
+static int32_t  doAppendRowFromTSRow(SSDataBlock* pBlock, STsdbReader* pReader, SRow* pTSRow,
+                                     STableBlockScanInfo* pScanInfo);
+static int32_t  doAppendRowFromFileBlock(SSDataBlock* pResBlock, STsdbReader* pReader, SBlockData* pBlockData,
+                                         int32_t rowIndex);
+static void     setComposedBlockFlag(STsdbReader* pReader, bool composed);
+static bool     hasBeenDropped(const SArray* pDelList, int32_t* index, int64_t key, int64_t ver, int32_t order,
+                               SVersionRange* pVerRange);
+
+static int32_t doMergeMemTableMultiRows(TSDBROW* pRow, uint64_t uid, SIterInfo* pIter, SArray* pDelList,
+                                        TSDBROW* pResRow, STsdbReader* pReader, bool* freeTSRow);
+static int32_t doMergeMemIMemRows(TSDBROW* pRow, TSDBROW* piRow, STableBlockScanInfo* pBlockScanInfo,
+                                  STsdbReader* pReader, SRow** pTSRow);
+static int32_t mergeRowsInFileBlocks(SBlockData* pBlockData, STableBlockScanInfo* pBlockScanInfo, int64_t key,
+                                     STsdbReader* pReader);
+
+static int32_t initDelSkylineIterator(STableBlockScanInfo* pBlockScanInfo, STsdbReader* pReader, STbData* pMemTbData,
+                                      STbData* piMemTbData);
+static STsdb*  getTsdbByRetentions(SVnode* pVnode, TSKEY winSKey, SRetention* retentions, const char* idstr,
+                                   int8_t* pLevel);
+static SVersionRange getQueryVerRange(SVnode* pVnode, SQueryTableDataCond* pCond, int8_t level);
+static bool          hasDataInLastBlock(SLastBlockReader* pLastBlockReader);
+static int32_t       doBuildDataBlock(STsdbReader* pReader);
+static TSDBKEY       getCurrentKeyInBuf(STableBlockScanInfo* pScanInfo, STsdbReader* pReader);
+static bool          hasDataInFileBlock(const SBlockData* pBlockData, const SFileBlockDumpInfo* pDumpInfo);
+static void          initBlockDumpInfo(STsdbReader* pReader, SDataBlockIter* pBlockIter);
+static int32_t       getInitialDelIndex(const SArray* pDelSkyline, int32_t order);
+
+static STableBlockScanInfo* getTableBlockScanInfo(SSHashObj* pTableMap, uint64_t uid, const char* id);
+
+static bool outOfTimeWindow(int64_t ts, STimeWindow* pWindow) { return (ts > pWindow->ekey) || (ts < pWindow->skey); }
+
+static int32_t setColumnIdSlotList(SBlockLoadSuppInfo* pSupInfo, SColumnInfo* pCols, const int32_t* pSlotIdList,
+                                   int32_t numOfCols) {
+  pSupInfo->smaValid = true;
+  pSupInfo->numOfCols = numOfCols;
+  pSupInfo->colId = taosMemoryMalloc(numOfCols * (sizeof(int16_t) * 2 + POINTER_BYTES));
+  if (pSupInfo->colId == NULL) {
+    taosMemoryFree(pSupInfo->colId);
+    return TSDB_CODE_OUT_OF_MEMORY;
+  }
+
+  pSupInfo->slotId = (int16_t*)((char*)pSupInfo->colId + (sizeof(int16_t) * numOfCols));
+  pSupInfo->buildBuf = (char**)((char*)pSupInfo->slotId + (sizeof(int16_t) * numOfCols));
+  for (int32_t i = 0; i < numOfCols; ++i) {
+    pSupInfo->colId[i] = pCols[i].colId;
+    pSupInfo->slotId[i] = pSlotIdList[i];
+
+    if (IS_VAR_DATA_TYPE(pCols[i].type)) {
+      pSupInfo->buildBuf[i] = taosMemoryMalloc(pCols[i].bytes);
+    } else {
+      pSupInfo->buildBuf[i] = NULL;
+    }
+  }
+
+  return TSDB_CODE_SUCCESS;
+}
+
+static int32_t updateBlockSMAInfo(STSchema* pSchema, SBlockLoadSuppInfo* pSupInfo) {
+  int32_t i = 0, j = 0;
+
+  while (i < pSchema->numOfCols && j < pSupInfo->numOfCols) {
+    STColumn* pTCol = &pSchema->columns[i];
+    if (pTCol->colId == pSupInfo->colId[j]) {
+      if (!IS_BSMA_ON(pTCol)) {
+        pSupInfo->smaValid = false;
+        return TSDB_CODE_SUCCESS;
+      }
+
+      i += 1;
+      j += 1;
+    } else if (pTCol->colId < pSupInfo->colId[j]) {
+      // do nothing
+      i += 1;
+    } else {
+      return TSDB_CODE_INVALID_PARA;
+    }
+  }
+
+  return TSDB_CODE_SUCCESS;
+}
+
+static int32_t initBlockScanInfoBuf(SBlockInfoBuf* pBuf, int32_t numOfTables) {
+  int32_t num = numOfTables / pBuf->numPerBucket;
+  int32_t remainder = numOfTables % pBuf->numPerBucket;
+  if (pBuf->pData == NULL) {
+    pBuf->pData = taosArrayInit(num + 1, POINTER_BYTES);
+  }
+
+  for (int32_t i = 0; i < num; ++i) {
+    char* p = taosMemoryCalloc(pBuf->numPerBucket, sizeof(STableBlockScanInfo));
+    if (p == NULL) {
+      return TSDB_CODE_OUT_OF_MEMORY;
+    }
+
+    taosArrayPush(pBuf->pData, &p);
+  }
+
+  if (remainder > 0) {
+    char* p = taosMemoryCalloc(remainder, sizeof(STableBlockScanInfo));
+    if (p == NULL) {
+      return TSDB_CODE_OUT_OF_MEMORY;
+    }
+    taosArrayPush(pBuf->pData, &p);
+  }
+
+  pBuf->numOfTables = numOfTables;
+
+  return TSDB_CODE_SUCCESS;
+}
+
+static int32_t ensureBlockScanInfoBuf(SBlockInfoBuf* pBuf, int32_t numOfTables) {
+  if (numOfTables <= pBuf->numOfTables) {
+    return TSDB_CODE_SUCCESS;
+  }
+
+  if (pBuf->numOfTables > 0) {
+    STableBlockScanInfo** p = (STableBlockScanInfo**)taosArrayPop(pBuf->pData);
+    taosMemoryFree(*p);
+    pBuf->numOfTables /= pBuf->numPerBucket;
+  }
+
+  int32_t num = (numOfTables - pBuf->numOfTables) / pBuf->numPerBucket;
+  int32_t remainder = (numOfTables - pBuf->numOfTables) % pBuf->numPerBucket;
+  if (pBuf->pData == NULL) {
+    pBuf->pData = taosArrayInit(num + 1, POINTER_BYTES);
+  }
+
+  for (int32_t i = 0; i < num; ++i) {
+    char* p = taosMemoryCalloc(pBuf->numPerBucket, sizeof(STableBlockScanInfo));
+    if (p == NULL) {
+      return TSDB_CODE_OUT_OF_MEMORY;
+    }
+
+    taosArrayPush(pBuf->pData, &p);
+  }
+
+  if (remainder > 0) {
+    char* p = taosMemoryCalloc(remainder, sizeof(STableBlockScanInfo));
+    if (p == NULL) {
+      return TSDB_CODE_OUT_OF_MEMORY;
+    }
+    taosArrayPush(pBuf->pData, &p);
+  }
+
+  pBuf->numOfTables = numOfTables;
+
+  return TSDB_CODE_SUCCESS;
+}
+
+static void clearBlockScanInfoBuf(SBlockInfoBuf* pBuf) {
+  size_t num = taosArrayGetSize(pBuf->pData);
+  for (int32_t i = 0; i < num; ++i) {
+    char** p = taosArrayGet(pBuf->pData, i);
+    taosMemoryFree(*p);
+  }
+
+  taosArrayDestroy(pBuf->pData);
+}
+
+static void* getPosInBlockInfoBuf(SBlockInfoBuf* pBuf, int32_t index) {
+  int32_t bucketIndex = index / pBuf->numPerBucket;
+  char**  pBucket = taosArrayGet(pBuf->pData, bucketIndex);
+  return (*pBucket) + (index % pBuf->numPerBucket) * sizeof(STableBlockScanInfo);
+}
+
+static int32_t uidComparFunc(const void* p1, const void* p2) {
+  uint64_t pu1 = *(uint64_t*)p1;
+  uint64_t pu2 = *(uint64_t*)p2;
+  if (pu1 == pu2) {
+    return 0;
+  } else {
+    return (pu1 < pu2) ? -1 : 1;
+  }
+}
+
+// NOTE: speedup the whole processing by preparing the buffer for STableBlockScanInfo in batch model
+static SSHashObj* createDataBlockScanInfo(STsdbReader* pTsdbReader, SBlockInfoBuf* pBuf, const STableKeyInfo* idList,
+                                          STableUidList* pUidList, int32_t numOfTables) {
+  // allocate buffer in order to load data blocks from file
+  // todo use simple hash instead, optimize the memory consumption
+  SSHashObj* pTableMap = tSimpleHashInit(numOfTables, taosGetDefaultHashFunction(TSDB_DATA_TYPE_BIGINT));
+  if (pTableMap == NULL) {
+    return NULL;
+  }
+
+  int64_t st = taosGetTimestampUs();
+  initBlockScanInfoBuf(pBuf, numOfTables);
+
+  pUidList->tableUidList = taosMemoryMalloc(numOfTables * sizeof(uint64_t));
+  if (pUidList->tableUidList == NULL) {
+    tSimpleHashCleanup(pTableMap);
+    return NULL;
+  }
+
+  pUidList->currentIndex = 0;
+
+  for (int32_t j = 0; j < numOfTables; ++j) {
+    STableBlockScanInfo* pScanInfo = getPosInBlockInfoBuf(pBuf, j);
+
+    pScanInfo->uid = idList[j].uid;
+    pUidList->tableUidList[j] = idList[j].uid;
+
+    if (ASCENDING_TRAVERSE(pTsdbReader->order)) {
+      int64_t skey = pTsdbReader->window.skey;
+      pScanInfo->lastKey = (skey > INT64_MIN) ? (skey - 1) : skey;
+      pScanInfo->lastKeyInStt = skey;
+    } else {
+      int64_t ekey = pTsdbReader->window.ekey;
+      pScanInfo->lastKey = (ekey < INT64_MAX) ? (ekey + 1) : ekey;
+      pScanInfo->lastKeyInStt = ekey;
+    }
+
+    tSimpleHashPut(pTableMap, &pScanInfo->uid, sizeof(uint64_t), &pScanInfo, POINTER_BYTES);
+    tsdbTrace("%p check table uid:%" PRId64 " from lastKey:%" PRId64 " %s", pTsdbReader, pScanInfo->uid,
+              pScanInfo->lastKey, pTsdbReader->idStr);
+  }
+
+  taosSort(pUidList->tableUidList, numOfTables, sizeof(uint64_t), uidComparFunc);
+
+  pTsdbReader->cost.createScanInfoList = (taosGetTimestampUs() - st) / 1000.0;
+  tsdbDebug("%p create %d tables scan-info, size:%.2f Kb, elapsed time:%.2f ms, %s", pTsdbReader, numOfTables,
+            (sizeof(STableBlockScanInfo) * numOfTables) / 1024.0, pTsdbReader->cost.createScanInfoList,
+            pTsdbReader->idStr);
+
+  return pTableMap;
+}
+
+static void resetAllDataBlockScanInfo(SSHashObj* pTableMap, int64_t ts, int32_t step) {
+  void   *p = NULL;
+  int32_t iter = 0;
+
+  while ((p = tSimpleHashIterate(pTableMap, p, &iter)) != NULL) {
+    STableBlockScanInfo* pInfo = *(STableBlockScanInfo**)p;
+
+    pInfo->iterInit = false;
+    pInfo->iter.hasVal = false;
+    pInfo->iiter.hasVal = false;
+
+    if (pInfo->iter.iter != NULL) {
+      pInfo->iter.iter = tsdbTbDataIterDestroy(pInfo->iter.iter);
+    }
+
+    if (pInfo->iiter.iter != NULL) {
+      pInfo->iiter.iter = tsdbTbDataIterDestroy(pInfo->iiter.iter);
+    }
+
+    pInfo->delSkyline = taosArrayDestroy(pInfo->delSkyline);
+    pInfo->lastKey = ts;
+    pInfo->lastKeyInStt = ts + step;
+  }
+}
+
+static void clearBlockScanInfo(STableBlockScanInfo* p) {
+  p->iterInit = false;
+
+  p->iter.hasVal = false;
+  p->iiter.hasVal = false;
+
+  if (p->iter.iter != NULL) {
+    p->iter.iter = tsdbTbDataIterDestroy(p->iter.iter);
+  }
+
+  if (p->iiter.iter != NULL) {
+    p->iiter.iter = tsdbTbDataIterDestroy(p->iiter.iter);
+  }
+
+  p->delSkyline = taosArrayDestroy(p->delSkyline);
+  p->pBlockList = taosArrayDestroy(p->pBlockList);
+  tMapDataClear(&p->mapData);
+}
+
+static void destroyAllBlockScanInfo(SSHashObj* pTableMap) {
+  void* p = NULL;
+  int32_t iter = 0;
+
+  while ((p = tSimpleHashIterate(pTableMap, p, &iter)) != NULL) {
+    clearBlockScanInfo(*(STableBlockScanInfo**)p);
+  }
+
+  tSimpleHashCleanup(pTableMap);
+}
+
+static bool isEmptyQueryTimeWindow(STimeWindow* pWindow) { return pWindow->skey > pWindow->ekey; }
+
+// Update the query time window according to the data time to live(TTL) information, in order to avoid to return
+// the expired data to client, even it is queried already.
+static STimeWindow updateQueryTimeWindow(STsdb* pTsdb, STimeWindow* pWindow) {
+  STsdbKeepCfg* pCfg = &pTsdb->keepCfg;
+
+  int64_t now = taosGetTimestamp(pCfg->precision);
+  int64_t earilyTs = now - (tsTickPerMin[pCfg->precision] * pCfg->keep2) + 1;  // needs to add one tick
+
+  STimeWindow win = *pWindow;
+  if (win.skey < earilyTs) {
+    win.skey = earilyTs;
+  }
+
+  return win;
+}
+
+// init file iterator
+static int32_t initFilesetIterator(SFilesetIter* pIter, SArray* aDFileSet, STsdbReader* pReader) {
+  size_t numOfFileset = taosArrayGetSize(aDFileSet);
+
+  pIter->index = ASCENDING_TRAVERSE(pReader->order) ? -1 : numOfFileset;
+  pIter->order = pReader->order;
+  pIter->pFileList = aDFileSet;
+  pIter->numOfFiles = numOfFileset;
+
+  if (pIter->pLastBlockReader == NULL) {
+    pIter->pLastBlockReader = taosMemoryCalloc(1, sizeof(struct SLastBlockReader));
+    if (pIter->pLastBlockReader == NULL) {
+      int32_t code = TSDB_CODE_OUT_OF_MEMORY;
+      tsdbError("failed to prepare the last block iterator, since:%s %s", tstrerror(code), pReader->idStr);
+      return code;
+    }
+  }
+
+  SLastBlockReader* pLReader = pIter->pLastBlockReader;
+  pLReader->order = pReader->order;
+  pLReader->window = pReader->window;
+  pLReader->verRange = pReader->verRange;
+
+  pLReader->uid = 0;
+  tMergeTreeClose(&pLReader->mergeTree);
+
+  if (pLReader->pInfo == NULL) {
+    // here we ignore the first column, which is always be the primary timestamp column
+    SBlockLoadSuppInfo* pInfo = &pReader->suppInfo;
+
+    int32_t numOfStt = pReader->pTsdb->pVnode->config.sttTrigger;
+    pLReader->pInfo = tCreateLastBlockLoadInfo(pReader->pSchema, &pInfo->colId[1], pInfo->numOfCols - 1, numOfStt);
+    if (pLReader->pInfo == NULL) {
+      tsdbDebug("init fileset iterator failed, code:%s %s", tstrerror(terrno), pReader->idStr);
+      return terrno;
+    }
+  }
+
+  tsdbDebug("init fileset iterator, total files:%d %s", pIter->numOfFiles, pReader->idStr);
+  return TSDB_CODE_SUCCESS;
+}
+
+static int32_t filesetIteratorNext(SFilesetIter* pIter, STsdbReader* pReader, bool* hasNext) {
+  bool    asc = ASCENDING_TRAVERSE(pIter->order);
+  int32_t step = asc ? 1 : -1;
+  pIter->index += step;
+  int32_t code = 0;
+
+  if ((asc && pIter->index >= pIter->numOfFiles) || ((!asc) && pIter->index < 0)) {
+    *hasNext = false;
+    return TSDB_CODE_SUCCESS;
+  }
+
+  SIOCostSummary* pSum = &pReader->cost;
+  getLastBlockLoadInfo(pIter->pLastBlockReader->pInfo, &pSum->lastBlockLoad, &pReader->cost.lastBlockLoadTime);
+
+  pIter->pLastBlockReader->uid = 0;
+  tMergeTreeClose(&pIter->pLastBlockReader->mergeTree);
+  resetLastBlockLoadInfo(pIter->pLastBlockReader->pInfo);
+
+  // check file the time range of coverage
+  STimeWindow win = {0};
+
+  while (1) {
+    if (pReader->pFileReader != NULL) {
+      tsdbDataFReaderClose(&pReader->pFileReader);
+    }
+
+    pReader->status.pCurrentFileset = (SDFileSet*)taosArrayGet(pIter->pFileList, pIter->index);
+
+    code = tsdbDataFReaderOpen(&pReader->pFileReader, pReader->pTsdb, pReader->status.pCurrentFileset);
+    if (code != TSDB_CODE_SUCCESS) {
+      goto _err;
+    }
+
+    pReader->cost.headFileLoad += 1;
+
+    int32_t fid = pReader->status.pCurrentFileset->fid;
+    tsdbFidKeyRange(fid, pReader->pTsdb->keepCfg.days, pReader->pTsdb->keepCfg.precision, &win.skey, &win.ekey);
+
+    // current file are no longer overlapped with query time window, ignore remain files
+    if ((asc && win.skey > pReader->window.ekey) || (!asc && win.ekey < pReader->window.skey)) {
+      tsdbDebug("%p remain files are not qualified for qrange:%" PRId64 "-%" PRId64 ", ignore, %s", pReader,
+                pReader->window.skey, pReader->window.ekey, pReader->idStr);
+      *hasNext = false;
+      return TSDB_CODE_SUCCESS;
+    }
+
+    if ((asc && (win.ekey < pReader->window.skey)) || ((!asc) && (win.skey > pReader->window.ekey))) {
+      pIter->index += step;
+      if ((asc && pIter->index >= pIter->numOfFiles) || ((!asc) && pIter->index < 0)) {
+        *hasNext = false;
+        return TSDB_CODE_SUCCESS;
+      }
+      continue;
+    }
+
+    tsdbDebug("%p file found fid:%d for qrange:%" PRId64 "-%" PRId64 ", %s", pReader, fid, pReader->window.skey,
+              pReader->window.ekey, pReader->idStr);
+    *hasNext = true;
+    return TSDB_CODE_SUCCESS;
+  }
+
+  _err:
+  *hasNext = false;
+  return code;
+}
+
+static void resetDataBlockIterator(SDataBlockIter* pIter, int32_t order) {
+  pIter->order = order;
+  pIter->index = -1;
+  pIter->numOfBlocks = 0;
+  if (pIter->blockList == NULL) {
+    pIter->blockList = taosArrayInit(4, sizeof(SFileDataBlockInfo));
+  } else {
+    taosArrayClear(pIter->blockList);
+  }
+}
+
+static void cleanupDataBlockIterator(SDataBlockIter* pIter) { taosArrayDestroy(pIter->blockList); }
+
+static void initReaderStatus(SReaderStatus* pStatus) {
+  pStatus->pTableIter = NULL;
+  pStatus->loadFromFile = true;
+}
+
+static SSDataBlock* createResBlock(SQueryTableDataCond* pCond, int32_t capacity) {
+  SSDataBlock* pResBlock = createDataBlock();
+  if (pResBlock == NULL) {
+    terrno = TSDB_CODE_OUT_OF_MEMORY;
+    return NULL;
+  }
+
+  for (int32_t i = 0; i < pCond->numOfCols; ++i) {
+    SColumnInfoData colInfo = {0};
+    colInfo.info = pCond->colList[i];
+    blockDataAppendColInfo(pResBlock, &colInfo);
+  }
+
+  int32_t code = blockDataEnsureCapacity(pResBlock, capacity);
+  if (code != TSDB_CODE_SUCCESS) {
+    terrno = code;
+    taosMemoryFree(pResBlock);
+    return NULL;
+  }
+  return pResBlock;
+}
+
+static int32_t tsdbInitReaderLock(STsdbReader* pReader) {
+  int32_t code = -1;
+  qTrace("tsdb/read: %p, pre-init read mutex: %p, code: %d", pReader, &pReader->readerMutex, code);
+
+  code = taosThreadMutexInit(&pReader->readerMutex, NULL);
+
+  qTrace("tsdb/read: %p, post-init read mutex: %p, code: %d", pReader, &pReader->readerMutex, code);
+
+  return code;
+}
+
+static int32_t tsdbUninitReaderLock(STsdbReader* pReader) {
+  int32_t code = -1;
+  qTrace("tsdb/read: %p, pre-uninit read mutex: %p, code: %d", pReader, &pReader->readerMutex, code);
+
+  code = taosThreadMutexDestroy(&pReader->readerMutex);
+
+  qTrace("tsdb/read: %p, post-uninit read mutex: %p, code: %d", pReader, &pReader->readerMutex, code);
+
+  return code;
+}
+
+static int32_t tsdbAcquireReader(STsdbReader* pReader) {
+  int32_t code = -1;
+  qTrace("tsdb/read: %p, pre-take read mutex: %p, code: %d", pReader, &pReader->readerMutex, code);
+
+  code = taosThreadMutexLock(&pReader->readerMutex);
+
+  qTrace("tsdb/read: %p, post-take read mutex: %p, code: %d", pReader, &pReader->readerMutex, code);
+
+  return code;
+}
+
+static int32_t tsdbTryAcquireReader(STsdbReader* pReader) {
+  int32_t code = -1;
+  qTrace("tsdb/read: %p, pre-trytake read mutex: %p, code: %d", pReader, &pReader->readerMutex, code);
+
+  code = taosThreadMutexTryLock(&pReader->readerMutex);
+
+  qTrace("tsdb/read: %p, post-trytake read mutex: %p, code: %d", pReader, &pReader->readerMutex, code);
+
+  return code;
+}
+
+static int32_t tsdbReleaseReader(STsdbReader* pReader) {
+  int32_t code = -1;
+  qTrace("tsdb/read: %p, pre-untake read mutex: %p, code: %d", pReader, &pReader->readerMutex, code);
+
+  code = taosThreadMutexUnlock(&pReader->readerMutex);
+
+  qTrace("tsdb/read: %p, post-untake read mutex: %p, code: %d", pReader, &pReader->readerMutex, code);
+
+  return code;
+}
+
+void tsdbReleaseDataBlock(STsdbReader* pReader) {
+  SReaderStatus* pStatus = &pReader->status;
+  if (!pStatus->composedDataBlock) {
+    tsdbReleaseReader(pReader);
+  }
+}
+
+static int32_t initResBlockInfo(SResultBlockInfo* pResBlockInfo, int64_t capacity, SSDataBlock* pResBlock, SQueryTableDataCond* pCond) {
+  pResBlockInfo->capacity = capacity;
+  pResBlockInfo->pResBlock = pResBlock;
+  terrno = 0;
+
+  if (pResBlockInfo->pResBlock == NULL) {
+    pResBlockInfo->freeBlock = true;
+    pResBlockInfo->pResBlock = createResBlock(pCond, pResBlockInfo->capacity);
+  } else {
+    pResBlockInfo->freeBlock = false;
+  }
+
+  return terrno;
+}
+
+static int32_t tsdbReaderCreate(SVnode* pVnode, SQueryTableDataCond* pCond, void** ppReader, int32_t capacity,
+                                SSDataBlock* pResBlock, const char* idstr) {
+  int32_t      code = 0;
+  int8_t       level = 0;
+  STsdbReader* pReader = (STsdbReader*)taosMemoryCalloc(1, sizeof(*pReader));
+  if (pReader == NULL) {
+    code = TSDB_CODE_OUT_OF_MEMORY;
+    goto _end;
+  }
+
+  if (VND_IS_TSMA(pVnode)) {
+    tsdbDebug("vgId:%d, tsma is selected to query, %s", TD_VID(pVnode), idstr);
+  }
+
+  initReaderStatus(&pReader->status);
+
+  pReader->pTsdb = getTsdbByRetentions(pVnode, pCond->twindows.skey, pVnode->config.tsdbCfg.retentions, idstr, &level);
+  pReader->suid = pCond->suid;
+  pReader->order = pCond->order;
+
+  pReader->idStr = (idstr != NULL) ? taosStrdup(idstr) : NULL;
+  pReader->verRange = getQueryVerRange(pVnode, pCond, level);
+  pReader->type = pCond->type;
+  pReader->window = updateQueryTimeWindow(pReader->pTsdb, &pCond->twindows);
+  pReader->blockInfoBuf.numPerBucket = 1000;  // 1000 tables per bucket
+
+  code = initResBlockInfo(&pReader->resBlockInfo, capacity, pResBlock, pCond);
+  if (code != TSDB_CODE_SUCCESS) {
+    goto _end;
+  }
+
+  if (pCond->numOfCols <= 0) {
+    tsdbError("vgId:%d, invalid column number %d in query cond, %s", TD_VID(pVnode), pCond->numOfCols, idstr);
+    code = TSDB_CODE_INVALID_PARA;
+    goto _end;
+  }
+
+  // allocate buffer in order to load data blocks from file
+  SBlockLoadSuppInfo* pSup = &pReader->suppInfo;
+  pSup->pColAgg = taosArrayInit(pCond->numOfCols, sizeof(SColumnDataAgg));
+  if (pSup->pColAgg == NULL) {
+    code = TSDB_CODE_OUT_OF_MEMORY;
+    goto _end;
+  }
+
+  pSup->tsColAgg.colId = PRIMARYKEY_TIMESTAMP_COL_ID;
+  setColumnIdSlotList(pSup, pCond->colList, pCond->pSlotList, pCond->numOfCols);
+
+  code = tBlockDataCreate(&pReader->status.fileBlockData);
+  if (code != TSDB_CODE_SUCCESS) {
+    terrno = code;
+    goto _end;
+  }
+
+  if (pReader->suppInfo.colId[0] != PRIMARYKEY_TIMESTAMP_COL_ID) {
+    tsdbError("the first column isn't primary timestamp, %d, %s", pReader->suppInfo.colId[0], pReader->idStr);
+    code = TSDB_CODE_INVALID_PARA;
+    goto _end;
+  }
+
+  pReader->status.pPrimaryTsCol = taosArrayGet(pReader->resBlockInfo.pResBlock->pDataBlock, pSup->slotId[0]);
+  int32_t type = pReader->status.pPrimaryTsCol->info.type;
+  if (type != TSDB_DATA_TYPE_TIMESTAMP) {
+    tsdbError("the first column isn't primary timestamp in result block, actual: %s, %s", tDataTypes[type].name,
+              pReader->idStr);
+    code = TSDB_CODE_INVALID_PARA;
+    goto _end;
+  }
+
+  tsdbInitReaderLock(pReader);
+
+  *ppReader = pReader;
+  return code;
+
+  _end:
+  tsdbReaderClose(pReader);
+  *ppReader = NULL;
+  return code;
+}
+
+static int32_t doLoadBlockIndex(STsdbReader* pReader, SDataFReader* pFileReader, SArray* pIndexList) {
+  int64_t    st = taosGetTimestampUs();
+  LRUHandle* handle = NULL;
+  int32_t    code = tsdbCacheGetBlockIdx(pFileReader->pTsdb->biCache, pFileReader, &handle);
+  if (code != TSDB_CODE_SUCCESS || handle == NULL) {
+    goto _end;
+  }
+
+  int32_t numOfTables = tSimpleHashGetSize(pReader->status.pTableMap);
+
+  SArray* aBlockIdx = (SArray*)taosLRUCacheValue(pFileReader->pTsdb->biCache, handle);
+  size_t  num = taosArrayGetSize(aBlockIdx);
+  if (num == 0) {
+    tsdbBICacheRelease(pFileReader->pTsdb->biCache, handle);
+    return TSDB_CODE_SUCCESS;
+  }
+
+  // todo binary search to the start position
+  int64_t et1 = taosGetTimestampUs();
+
+  SBlockIdx*     pBlockIdx = NULL;
+  STableUidList* pList = &pReader->status.uidList;
+
+  int32_t i = 0, j = 0;
+  while (i < num && j < numOfTables) {
+    pBlockIdx = (SBlockIdx*)taosArrayGet(aBlockIdx, i);
+    if (pBlockIdx->suid != pReader->suid) {
+      i += 1;
+      continue;
+    }
+
+    if (pBlockIdx->uid < pList->tableUidList[j]) {
+      i += 1;
+      continue;
+    }
+
+    if (pBlockIdx->uid > pList->tableUidList[j]) {
+      j += 1;
+      continue;
+    }
+
+    if (pBlockIdx->uid == pList->tableUidList[j]) {
+      // this block belongs to a table that is not queried.
+      STableBlockScanInfo* pScanInfo = getTableBlockScanInfo(pReader->status.pTableMap, pBlockIdx->uid, pReader->idStr);
+      if (pScanInfo == NULL) {
+        tsdbBICacheRelease(pFileReader->pTsdb->biCache, handle);
+        return terrno;
+      }
+
+      if (pScanInfo->pBlockList == NULL) {
+        pScanInfo->pBlockList = taosArrayInit(4, sizeof(SBlockIndex));
+      }
+
+      taosArrayPush(pIndexList, pBlockIdx);
+
+      i += 1;
+      j += 1;
+    }
+  }
+
+  int64_t et2 = taosGetTimestampUs();
+  tsdbDebug("load block index for %d/%d tables completed, elapsed time:%.2f ms, set blockIdx:%.2f ms, size:%.2f Kb %s",
+            numOfTables, (int32_t)num, (et1 - st) / 1000.0, (et2 - et1) / 1000.0, num * sizeof(SBlockIdx) / 1024.0,
+            pReader->idStr);
+
+  pReader->cost.headFileLoadTime += (et1 - st) / 1000.0;
+
+  _end:
+  tsdbBICacheRelease(pFileReader->pTsdb->biCache, handle);
+  return code;
+}
+
+static void doCleanupTableScanInfo(STableBlockScanInfo* pScanInfo) {
+  // reset the index in last block when handing a new file
+  tMapDataClear(&pScanInfo->mapData);
+  taosArrayClear(pScanInfo->pBlockList);
+}
+
+static void cleanupTableScanInfo(SReaderStatus* pStatus) {
+  if (pStatus->mapDataCleaned) {
+    return;
+  }
+
+  SSHashObj* pTableMap = pStatus->pTableMap;
+  STableBlockScanInfo** px = NULL;
+  int32_t iter = 0;
+
+  while (1) {
+    px = tSimpleHashIterate(pTableMap, px, &iter);
+    if (px == NULL) {
+      break;
+    }
+
+    doCleanupTableScanInfo(*px);
+  }
+
+  pStatus->mapDataCleaned = true;
+}
+
+static int32_t doLoadFileBlock(STsdbReader* pReader, SArray* pIndexList, SBlockNumber* pBlockNum, SArray* pTableScanInfoList) {
+  size_t  sizeInDisk = 0;
+  size_t  numOfTables = taosArrayGetSize(pIndexList);
+
+  int64_t st = taosGetTimestampUs();
+  cleanupTableScanInfo(&pReader->status);
+
+  // set the flag for the new file
+  pReader->status.mapDataCleaned = false;
+  for (int32_t i = 0; i < numOfTables; ++i) {
+    SBlockIdx*           pBlockIdx = taosArrayGet(pIndexList, i);
+    STableBlockScanInfo* pScanInfo = getTableBlockScanInfo(pReader->status.pTableMap, pBlockIdx->uid, pReader->idStr);
+    if (pScanInfo == NULL) {
+      return terrno;
+    }
+
+    tMapDataReset(&pScanInfo->mapData);
+    tsdbReadDataBlk(pReader->pFileReader, pBlockIdx, &pScanInfo->mapData);
+    taosArrayEnsureCap(pScanInfo->pBlockList, pScanInfo->mapData.nItem);
+
+    sizeInDisk += pScanInfo->mapData.nData;
+
+    int32_t     step = ASCENDING_TRAVERSE(pReader->order) ? 1 : -1;
+    STimeWindow w = pReader->window;
+    if (ASCENDING_TRAVERSE(pReader->order)) {
+      w.skey = pScanInfo->lastKey + step;
+    } else {
+      w.ekey = pScanInfo->lastKey + step;
+    }
+
+    if (isEmptyQueryTimeWindow(&w)) {
+      continue;
+    }
+
+    SDataBlk block = {0};
+    for (int32_t j = 0; j < pScanInfo->mapData.nItem; ++j) {
+      tGetDataBlk(pScanInfo->mapData.pData + pScanInfo->mapData.aOffset[j], &block);
+
+      // 1. time range check
+      // if (block.minKey.ts > pReader->window.ekey || block.maxKey.ts < pReader->window.skey) {
+      if (block.minKey.ts > w.ekey || block.maxKey.ts < w.skey) {
+        continue;
+      }
+
+      // 2. version range check
+      if (block.minVer > pReader->verRange.maxVer || block.maxVer < pReader->verRange.minVer) {
+        continue;
+      }
+
+      SBlockIndex bIndex = {.ordinalIndex = j, .inFileOffset = block.aSubBlock->offset};
+      bIndex.window = (STimeWindow){.skey = block.minKey.ts, .ekey = block.maxKey.ts};
+
+      void* p1 = taosArrayPush(pScanInfo->pBlockList, &bIndex);
+      if (p1 == NULL) {
+        tMapDataClear(&pScanInfo->mapData);
+        return TSDB_CODE_OUT_OF_MEMORY;
+      }
+
+      pBlockNum->numOfBlocks += 1;
+    }
+
+    if (taosArrayGetSize(pScanInfo->pBlockList) > 0) {
+      taosArrayPush(pTableScanInfoList, &pScanInfo);
+    }
+  }
+
+  pBlockNum->numOfLastFiles = pReader->pFileReader->pSet->nSttF;
+  int32_t total = pBlockNum->numOfLastFiles + pBlockNum->numOfBlocks;
+
+  double el = (taosGetTimestampUs() - st) / 1000.0;
+  tsdbDebug(
+      "load block of %ld tables completed, blocks:%d in %d tables, last-files:%d, block-info-size:%.2f Kb, elapsed "
+      "time:%.2f ms %s",
+      numOfTables, pBlockNum->numOfBlocks, (int32_t)taosArrayGetSize(pTableScanInfoList), pBlockNum->numOfLastFiles,
+      sizeInDisk / 1000.0, el, pReader->idStr);
+
+  pReader->cost.numOfBlocks += total;
+  pReader->cost.headFileLoadTime += el;
+
+  return TSDB_CODE_SUCCESS;
+}
+
+static void setBlockAllDumped(SFileBlockDumpInfo* pDumpInfo, int64_t maxKey, int32_t order) {
+  int32_t step = ASCENDING_TRAVERSE(order) ? 1 : -1;
+  pDumpInfo->allDumped = true;
+  pDumpInfo->lastKey = maxKey + step;
+}
+
+static int32_t doCopyColVal(SColumnInfoData* pColInfoData, int32_t rowIndex, int32_t colIndex, SColVal* pColVal,
+                            SBlockLoadSuppInfo* pSup) {
+  if (IS_VAR_DATA_TYPE(pColVal->type)) {
+    if (!COL_VAL_IS_VALUE(pColVal)) {
+      colDataSetNULL(pColInfoData, rowIndex);
+    } else {
+      varDataSetLen(pSup->buildBuf[colIndex], pColVal->value.nData);
+      if (pColVal->value.nData > pColInfoData->info.bytes) {
+        tsdbWarn("column cid:%d actual data len %d is bigger than schema len %d", pColVal->cid, pColVal->value.nData,
+                 pColInfoData->info.bytes);
+        return TSDB_CODE_TDB_INVALID_TABLE_SCHEMA_VER;
+      }
+      if (pColVal->value.nData > 0) {  // pData may be null, if nData is 0
+        memcpy(varDataVal(pSup->buildBuf[colIndex]), pColVal->value.pData, pColVal->value.nData);
+      }
+
+      colDataSetVal(pColInfoData, rowIndex, pSup->buildBuf[colIndex], false);
+    }
+  } else {
+    colDataSetVal(pColInfoData, rowIndex, (const char*)&pColVal->value, !COL_VAL_IS_VALUE(pColVal));
+  }
+
+  return TSDB_CODE_SUCCESS;
+}
+
+static SFileDataBlockInfo* getCurrentBlockInfo(SDataBlockIter* pBlockIter) {
+  size_t num = taosArrayGetSize(pBlockIter->blockList);
+  if (num == 0) {
+    ASSERT(pBlockIter->numOfBlocks == num);
+    return NULL;
+  }
+
+  SFileDataBlockInfo* pBlockInfo = taosArrayGet(pBlockIter->blockList, pBlockIter->index);
+  return pBlockInfo;
+}
+
+static SDataBlk* getCurrentBlock(SDataBlockIter* pBlockIter) { return &pBlockIter->block; }
+
+static int doBinarySearchKey(TSKEY* keyList, int num, int pos, TSKEY key, int order) {
+  // start end position
+  int s, e;
+  s = pos;
+
+  // check
+  ASSERT(pos >= 0 && pos < num && num > 0);
+  if (order == TSDB_ORDER_ASC) {
+    // find the first position which is smaller than the key
+    e = num - 1;
+    if (key < keyList[pos]) return -1;
+    while (1) {
+      // check can return
+      if (key >= keyList[e]) return e;
+      if (key <= keyList[s]) return s;
+      if (e - s <= 1) return s;
+
+      // change start or end position
+      int mid = s + (e - s + 1) / 2;
+      if (keyList[mid] > key)
+        e = mid;
+      else if (keyList[mid] < key)
+        s = mid;
+      else
+        return mid;
+    }
+  } else {  // DESC
+    // find the first position which is bigger than the key
+    e = 0;
+    if (key > keyList[pos]) return -1;
+    while (1) {
+      // check can return
+      if (key <= keyList[e]) return e;
+      if (key >= keyList[s]) return s;
+      if (s - e <= 1) return s;
+
+      // change start or end position
+      int mid = s - (s - e + 1) / 2;
+      if (keyList[mid] < key)
+        e = mid;
+      else if (keyList[mid] > key)
+        s = mid;
+      else
+        return mid;
+    }
+  }
+}
+
+static int32_t getEndPosInDataBlock(STsdbReader* pReader, SBlockData* pBlockData, SDataBlk* pBlock, int32_t pos) {
+  // NOTE: reverse the order to find the end position in data block
+  int32_t endPos = -1;
+  bool    asc = ASCENDING_TRAVERSE(pReader->order);
+
+  if (asc && pReader->window.ekey >= pBlock->maxKey.ts) {
+    endPos = pBlock->nRow - 1;
+  } else if (!asc && pReader->window.skey <= pBlock->minKey.ts) {
+    endPos = 0;
+  } else {
+    int64_t key = asc ? pReader->window.ekey : pReader->window.skey;
+    endPos = doBinarySearchKey(pBlockData->aTSKEY, pBlock->nRow, pos, key, pReader->order);
+  }
+
+  if ((pReader->verRange.maxVer >= pBlock->minVer && pReader->verRange.maxVer < pBlock->maxVer)||
+      (pReader->verRange.minVer <= pBlock->maxVer && pReader->verRange.minVer > pBlock->minVer)) {
+    int32_t i = endPos;
+
+    if (asc) {
+      for(; i >= 0; --i) {
+        if (pBlockData->aVersion[i] <= pReader->verRange.maxVer) {
+          break;
+        }
+      }
+    } else {
+      for(; i < pBlock->nRow; ++i) {
+        if (pBlockData->aVersion[i] >= pReader->verRange.minVer) {
+          break;
+        }
+      }
+    }
+
+    endPos = i;
+  }
+
+  return endPos;
+}
+
+static void copyPrimaryTsCol(const SBlockData* pBlockData, SFileBlockDumpInfo* pDumpInfo, SColumnInfoData* pColData,
+                             int32_t dumpedRows, bool asc) {
+  if (asc) {
+    memcpy(pColData->pData, &pBlockData->aTSKEY[pDumpInfo->rowIndex], dumpedRows * sizeof(int64_t));
+  } else {
+    int32_t startIndex = pDumpInfo->rowIndex - dumpedRows + 1;
+    memcpy(pColData->pData, &pBlockData->aTSKEY[startIndex], dumpedRows * sizeof(int64_t));
+
+    // todo: opt perf by extract the loop
+    // reverse the array list
+    int32_t  mid = dumpedRows >> 1u;
+    int64_t* pts = (int64_t*)pColData->pData;
+    for (int32_t j = 0; j < mid; ++j) {
+      int64_t t = pts[j];
+      pts[j] = pts[dumpedRows - j - 1];
+      pts[dumpedRows - j - 1] = t;
+    }
+  }
+}
+
+// a faster version of copy procedure.
+static void copyNumericCols(const SColData* pData, SFileBlockDumpInfo* pDumpInfo, SColumnInfoData* pColData,
+                            int32_t dumpedRows, bool asc) {
+  uint8_t* p = NULL;
+  if (asc) {
+    p = pData->pData + tDataTypes[pData->type].bytes * pDumpInfo->rowIndex;
+  } else {
+    int32_t startIndex = pDumpInfo->rowIndex - dumpedRows + 1;
+    p = pData->pData + tDataTypes[pData->type].bytes * startIndex;
+  }
+
+  int32_t step = asc ? 1 : -1;
+
+  // make sure it is aligned to 8bit, the allocated memory address is aligned to 256bit
+  //  ASSERT((((uint64_t)pColData->pData) & (0x8 - 1)) == 0);
+
+  // 1. copy data in a batch model
+  memcpy(pColData->pData, p, dumpedRows * tDataTypes[pData->type].bytes);
+
+  // 2. reverse the array list in case of descending order scan data block
+  if (!asc) {
+    switch (pColData->info.type) {
+      case TSDB_DATA_TYPE_TIMESTAMP:
+      case TSDB_DATA_TYPE_DOUBLE:
+      case TSDB_DATA_TYPE_BIGINT:
+      case TSDB_DATA_TYPE_UBIGINT: {
+        int32_t  mid = dumpedRows >> 1u;
+        int64_t* pts = (int64_t*)pColData->pData;
+        for (int32_t j = 0; j < mid; ++j) {
+          int64_t t = pts[j];
+          pts[j] = pts[dumpedRows - j - 1];
+          pts[dumpedRows - j - 1] = t;
+        }
+        break;
+      }
+
+      case TSDB_DATA_TYPE_BOOL:
+      case TSDB_DATA_TYPE_TINYINT:
+      case TSDB_DATA_TYPE_UTINYINT: {
+        int32_t mid = dumpedRows >> 1u;
+        int8_t* pts = (int8_t*)pColData->pData;
+        for (int32_t j = 0; j < mid; ++j) {
+          int8_t t = pts[j];
+          pts[j] = pts[dumpedRows - j - 1];
+          pts[dumpedRows - j - 1] = t;
+        }
+        break;
+      }
+
+      case TSDB_DATA_TYPE_SMALLINT:
+      case TSDB_DATA_TYPE_USMALLINT: {
+        int32_t  mid = dumpedRows >> 1u;
+        int16_t* pts = (int16_t*)pColData->pData;
+        for (int32_t j = 0; j < mid; ++j) {
+          int64_t t = pts[j];
+          pts[j] = pts[dumpedRows - j - 1];
+          pts[dumpedRows - j - 1] = t;
+        }
+        break;
+      }
+
+      case TSDB_DATA_TYPE_FLOAT:
+      case TSDB_DATA_TYPE_INT:
+      case TSDB_DATA_TYPE_UINT: {
+        int32_t  mid = dumpedRows >> 1u;
+        int32_t* pts = (int32_t*)pColData->pData;
+        for (int32_t j = 0; j < mid; ++j) {
+          int32_t t = pts[j];
+          pts[j] = pts[dumpedRows - j - 1];
+          pts[dumpedRows - j - 1] = t;
+        }
+        break;
+      }
+    }
+  }
+
+  // 3. if the  null value exists, check items one-by-one
+  if (pData->flag != HAS_VALUE) {
+    int32_t rowIndex = 0;
+
+    for (int32_t j = pDumpInfo->rowIndex; rowIndex < dumpedRows; j += step, rowIndex++) {
+      uint8_t v = tColDataGetBitValue(pData, j);
+      if (v == 0 || v == 1) {
+        colDataSetNull_f(pColData->nullbitmap, rowIndex);
+        pColData->hasNull = true;
+      }
+    }
+  }
+}
+
+static int32_t copyBlockDataToSDataBlock(STsdbReader* pReader) {
+  SReaderStatus*      pStatus = &pReader->status;
+  SDataBlockIter*     pBlockIter = &pStatus->blockIter;
+  SBlockLoadSuppInfo* pSupInfo = &pReader->suppInfo;
+  SFileBlockDumpInfo* pDumpInfo = &pReader->status.fBlockDumpInfo;
+
+  SBlockData*         pBlockData = &pStatus->fileBlockData;
+  SFileDataBlockInfo* pBlockInfo = getCurrentBlockInfo(pBlockIter);
+  SDataBlk*           pBlock = getCurrentBlock(pBlockIter);
+  SSDataBlock*        pResBlock = pReader->resBlockInfo.pResBlock;
+  int32_t             numOfOutputCols = pSupInfo->numOfCols;
+  int32_t             code = TSDB_CODE_SUCCESS;
+
+  SColVal cv = {0};
+  int64_t st = taosGetTimestampUs();
+  bool    asc = ASCENDING_TRAVERSE(pReader->order);
+  int32_t step = asc ? 1 : -1;
+
+  // no data exists, return directly.
+  if (pBlockData->nRow == 0 || pBlockData->aTSKEY == 0) {
+    tsdbWarn("%p no need to copy since no data in blockData, table uid:%" PRIu64 " has been dropped, %s", pReader,
+             pBlockInfo->uid, pReader->idStr);
+    pResBlock->info.rows = 0;
+    return 0;
+  }
+
+  // row index of dump info remain the initial position, let's find the appropriate start position.
+  if ((pDumpInfo->rowIndex == 0 && asc) || (pDumpInfo->rowIndex == pBlock->nRow - 1 && (!asc))) {
+    if (asc && pReader->window.skey <= pBlock->minKey.ts && pReader->verRange.minVer <= pBlock->minVer) {
+      // pDumpInfo->rowIndex = 0;
+    } else if (!asc && pReader->window.ekey >= pBlock->maxKey.ts && pReader->verRange.maxVer >= pBlock->maxVer) {
+      // pDumpInfo->rowIndex = pBlock->nRow - 1;
+    } else {  // find the appropriate the start position in current block, and set it to be the current rowIndex
+      int32_t pos = asc ? pBlock->nRow - 1 : 0;
+      int32_t order = asc ? TSDB_ORDER_DESC : TSDB_ORDER_ASC;
+      int64_t key = asc ? pReader->window.skey : pReader->window.ekey;
+      pDumpInfo->rowIndex = doBinarySearchKey(pBlockData->aTSKEY, pBlock->nRow, pos, key, order);
+
+      if (pDumpInfo->rowIndex < 0) {
+        tsdbError(
+            "%p failed to locate the start position in current block, global index:%d, table index:%d, brange:%" PRId64
+            "-%" PRId64 ", minVer:%" PRId64 ", maxVer:%" PRId64 " %s",
+            pReader, pBlockIter->index, pBlockInfo->tbBlockIdx, pBlock->minKey.ts, pBlock->maxKey.ts, pBlock->minVer,
+            pBlock->maxVer, pReader->idStr);
+        return TSDB_CODE_INVALID_PARA;
+      }
+
+      ASSERT(pReader->verRange.minVer <= pBlock->maxVer && pReader->verRange.maxVer >= pBlock->minVer);
+
+      // find the appropriate start position that satisfies the version requirement.
+      if ((pReader->verRange.maxVer >= pBlock->minVer && pReader->verRange.maxVer < pBlock->maxVer)||
+          (pReader->verRange.minVer <= pBlock->maxVer && pReader->verRange.minVer > pBlock->minVer)) {
+        int32_t i = pDumpInfo->rowIndex;
+        if (asc) {
+          for(; i < pBlock->nRow; ++i) {
+            if (pBlockData->aVersion[i] >= pReader->verRange.minVer) {
+              break;
+            }
+          }
+        } else {
+          for(; i >= 0; --i) {
+            if (pBlockData->aVersion[i] <= pReader->verRange.maxVer) {
+              break;
+            }
+          }
+        }
+
+        pDumpInfo->rowIndex = i;
+      }
+    }
+  }
+
+  // time window check
+  int32_t endIndex = getEndPosInDataBlock(pReader, pBlockData, pBlock, pDumpInfo->rowIndex);
+  if (endIndex == -1) {
+    setBlockAllDumped(pDumpInfo, pReader->window.ekey, pReader->order);
+    return TSDB_CODE_SUCCESS;
+  }
+
+  endIndex += step;
+  int32_t dumpedRows = asc ? (endIndex - pDumpInfo->rowIndex) : (pDumpInfo->rowIndex - endIndex);
+  if (dumpedRows > pReader->resBlockInfo.capacity) {  // output buffer check
+    dumpedRows = pReader->resBlockInfo.capacity;
+  } else if (dumpedRows <= 0) {  // no qualified rows in current data block, abort directly.
+    setBlockAllDumped(pDumpInfo, pReader->window.ekey, pReader->order);
+    return TSDB_CODE_SUCCESS;
+  }
+
+  int32_t i = 0;
+  int32_t rowIndex = 0;
+
+  SColumnInfoData* pColData = taosArrayGet(pResBlock->pDataBlock, pSupInfo->slotId[i]);
+  if (pSupInfo->colId[i] == PRIMARYKEY_TIMESTAMP_COL_ID) {
+    copyPrimaryTsCol(pBlockData, pDumpInfo, pColData, dumpedRows, asc);
+    i += 1;
+  }
+
+  int32_t colIndex = 0;
+  int32_t num = pBlockData->nColData;
+  while (i < numOfOutputCols && colIndex < num) {
+    rowIndex = 0;
+
+    SColData* pData = tBlockDataGetColDataByIdx(pBlockData, colIndex);
+    if (pData->cid < pSupInfo->colId[i]) {
+      colIndex += 1;
+    } else if (pData->cid == pSupInfo->colId[i]) {
+      pColData = taosArrayGet(pResBlock->pDataBlock, pSupInfo->slotId[i]);
+
+      if (pData->flag == HAS_NONE || pData->flag == HAS_NULL || pData->flag == (HAS_NULL | HAS_NONE)) {
+        colDataSetNNULL(pColData, 0, dumpedRows);
+      } else {
+        if (IS_MATHABLE_TYPE(pColData->info.type)) {
+          copyNumericCols(pData, pDumpInfo, pColData, dumpedRows, asc);
+        } else {  // varchar/nchar type
+          for (int32_t j = pDumpInfo->rowIndex; rowIndex < dumpedRows; j += step) {
+            tColDataGetValue(pData, j, &cv);
+            code = doCopyColVal(pColData, rowIndex++, i, &cv, pSupInfo);
+            if (code) {
+              return code;
+            }
+          }
+        }
+      }
+
+      colIndex += 1;
+      i += 1;
+    } else {  // the specified column does not exist in file block, fill with null data
+      pColData = taosArrayGet(pResBlock->pDataBlock, pSupInfo->slotId[i]);
+      colDataSetNNULL(pColData, 0, dumpedRows);
+      i += 1;
+    }
+  }
+
+  // fill the mis-matched columns with null value
+  while (i < numOfOutputCols) {
+    pColData = taosArrayGet(pResBlock->pDataBlock, pSupInfo->slotId[i]);
+    colDataSetNNULL(pColData, 0, dumpedRows);
+    i += 1;
+  }
+
+  pResBlock->info.dataLoad = 1;
+  pResBlock->info.rows = dumpedRows;
+  pDumpInfo->rowIndex += step * dumpedRows;
+
+  // check if current block are all handled
+  if (pDumpInfo->rowIndex >= 0 && pDumpInfo->rowIndex < pBlock->nRow) {
+    int64_t ts = pBlockData->aTSKEY[pDumpInfo->rowIndex];
+    if (outOfTimeWindow(ts, &pReader->window)) {  // the remain data has out of query time window, ignore current block
+      setBlockAllDumped(pDumpInfo, ts, pReader->order);
+    }
+  } else {
+    int64_t ts = asc ? pBlock->maxKey.ts : pBlock->minKey.ts;
+    setBlockAllDumped(pDumpInfo, ts, pReader->order);
+  }
+
+  double elapsedTime = (taosGetTimestampUs() - st) / 1000.0;
+  pReader->cost.blockLoadTime += elapsedTime;
+
+  int32_t unDumpedRows = asc ? pBlock->nRow - pDumpInfo->rowIndex : pDumpInfo->rowIndex + 1;
+  tsdbDebug("%p copy file block to sdatablock, global index:%d, table index:%d, brange:%" PRId64 "-%" PRId64
+                ", rows:%d, remain:%d, minVer:%" PRId64 ", maxVer:%" PRId64 ", uid:%" PRIu64 " elapsed time:%.2f ms, %s",
+            pReader, pBlockIter->index, pBlockInfo->tbBlockIdx, pBlock->minKey.ts, pBlock->maxKey.ts, dumpedRows,
+            unDumpedRows, pBlock->minVer, pBlock->maxVer, pBlockInfo->uid, elapsedTime, pReader->idStr);
+
+  return TSDB_CODE_SUCCESS;
+}
+
+static FORCE_INLINE STSchema* getTableSchemaImpl(STsdbReader* pReader, uint64_t uid) {
+  ASSERT(pReader->pSchema == NULL);
+
+  int32_t code = metaGetTbTSchemaEx(pReader->pTsdb->pVnode->pMeta, pReader->suid, uid, -1, &pReader->pSchema);
+  if (code != TSDB_CODE_SUCCESS || pReader->pSchema == NULL) {
+    terrno = code;
+    tsdbError("failed to get table schema, uid:%" PRIu64 ", it may have been dropped, ver:-1, %s", uid, pReader->idStr);
+    return NULL;
+  }
+
+  code = tsdbRowMergerInit(&pReader->status.merger, pReader->pSchema);
+  if (code != TSDB_CODE_SUCCESS) {
+    terrno = code;
+    tsdbError("failed to init merger, code:%s, %s", tstrerror(code), pReader->idStr);
+    return NULL;
+  }
+
+  return pReader->pSchema;
+}
+
+static int32_t doLoadFileBlockData(STsdbReader* pReader, SDataBlockIter* pBlockIter, SBlockData* pBlockData,
+                                   uint64_t uid) {
+  int32_t   code = 0;
+  STSchema* pSchema = pReader->pSchema;
+  int64_t   st = taosGetTimestampUs();
+
+  tBlockDataReset(pBlockData);
+
+  if (pReader->pSchema == NULL) {
+    pSchema = getTableSchemaImpl(pReader, uid);
+    if (pSchema == NULL) {
+      tsdbDebug("%p table uid:%" PRIu64 " has been dropped, no data existed, %s", pReader, uid, pReader->idStr);
+      return code;
+    }
+  }
+
+  SBlockLoadSuppInfo* pSup = &pReader->suppInfo;
+  TABLEID             tid = {.suid = pReader->suid, .uid = uid};
+  code = tBlockDataInit(pBlockData, &tid, pSchema, &pSup->colId[1], pSup->numOfCols - 1);
+  if (code != TSDB_CODE_SUCCESS) {
+    return code;
+  }
+
+  SFileDataBlockInfo* pBlockInfo = getCurrentBlockInfo(pBlockIter);
+  SFileBlockDumpInfo* pDumpInfo = &pReader->status.fBlockDumpInfo;
+
+  SDataBlk* pBlock = getCurrentBlock(pBlockIter);
+  code = tsdbReadDataBlock(pReader->pFileReader, pBlock, pBlockData);
+  if (code != TSDB_CODE_SUCCESS) {
+    tsdbError("%p error occurs in loading file block, global index:%d, table index:%d, brange:%" PRId64 "-%" PRId64
+                  ", rows:%d, code:%s %s",
+              pReader, pBlockIter->index, pBlockInfo->tbBlockIdx, pBlock->minKey.ts, pBlock->maxKey.ts, pBlock->nRow,
+              tstrerror(code), pReader->idStr);
+    return code;
+  }
+
+  double elapsedTime = (taosGetTimestampUs() - st) / 1000.0;
+
+  tsdbDebug("%p load file block into buffer, global index:%d, index in table block list:%d, brange:%" PRId64 "-%" PRId64
+                ", rows:%d, minVer:%" PRId64 ", maxVer:%" PRId64 ", elapsed time:%.2f ms, %s",
+            pReader, pBlockIter->index, pBlockInfo->tbBlockIdx, pBlock->minKey.ts, pBlock->maxKey.ts, pBlock->nRow,
+            pBlock->minVer, pBlock->maxVer, elapsedTime, pReader->idStr);
+
+  pReader->cost.blockLoadTime += elapsedTime;
+  pDumpInfo->allDumped = false;
+
+  return TSDB_CODE_SUCCESS;
+}
+
+static void cleanupBlockOrderSupporter(SBlockOrderSupporter* pSup) {
+  taosMemoryFreeClear(pSup->numOfBlocksPerTable);
+  taosMemoryFreeClear(pSup->indexPerTable);
+
+  for (int32_t i = 0; i < pSup->numOfTables; ++i) {
+    SBlockOrderWrapper* pBlockInfo = pSup->pDataBlockInfo[i];
+    taosMemoryFreeClear(pBlockInfo);
+  }
+
+  taosMemoryFreeClear(pSup->pDataBlockInfo);
+}
+
+static int32_t initBlockOrderSupporter(SBlockOrderSupporter* pSup, int32_t numOfTables) {
+  pSup->numOfBlocksPerTable = taosMemoryCalloc(1, sizeof(int32_t) * numOfTables);
+  pSup->indexPerTable = taosMemoryCalloc(1, sizeof(int32_t) * numOfTables);
+  pSup->pDataBlockInfo = taosMemoryCalloc(1, POINTER_BYTES * numOfTables);
+
+  if (pSup->numOfBlocksPerTable == NULL || pSup->indexPerTable == NULL || pSup->pDataBlockInfo == NULL) {
+    cleanupBlockOrderSupporter(pSup);
+    return TSDB_CODE_OUT_OF_MEMORY;
+  }
+
+  return TSDB_CODE_SUCCESS;
+}
+
+static int32_t fileDataBlockOrderCompar(const void* pLeft, const void* pRight, void* param) {
+  int32_t leftIndex = *(int32_t*)pLeft;
+  int32_t rightIndex = *(int32_t*)pRight;
+
+  SBlockOrderSupporter* pSupporter = (SBlockOrderSupporter*)param;
+
+  int32_t leftTableBlockIndex = pSupporter->indexPerTable[leftIndex];
+  int32_t rightTableBlockIndex = pSupporter->indexPerTable[rightIndex];
+
+  if (leftTableBlockIndex > pSupporter->numOfBlocksPerTable[leftIndex]) {
+    /* left block is empty */
+    return 1;
+  } else if (rightTableBlockIndex > pSupporter->numOfBlocksPerTable[rightIndex]) {
+    /* right block is empty */
+    return -1;
+  }
+
+  SBlockOrderWrapper* pLeftBlock = &pSupporter->pDataBlockInfo[leftIndex][leftTableBlockIndex];
+  SBlockOrderWrapper* pRightBlock = &pSupporter->pDataBlockInfo[rightIndex][rightTableBlockIndex];
+
+  return pLeftBlock->offset > pRightBlock->offset ? 1 : -1;
+}
+
+static int32_t doSetCurrentBlock(SDataBlockIter* pBlockIter, const char* idStr) {
+  SFileDataBlockInfo* pBlockInfo = getCurrentBlockInfo(pBlockIter);
+  if (pBlockInfo != NULL) {
+    STableBlockScanInfo* pScanInfo = getTableBlockScanInfo(pBlockIter->pTableMap, pBlockInfo->uid, idStr);
+    if (pScanInfo == NULL) {
+      return terrno;
+    }
+
+    SBlockIndex* pIndex = taosArrayGet(pScanInfo->pBlockList, pBlockInfo->tbBlockIdx);
+    tMapDataGetItemByIdx(&pScanInfo->mapData, pIndex->ordinalIndex, &pBlockIter->block, tGetDataBlk);
+  }
+
+#if 0
+  qDebug("check file block, table uid:%"PRIu64" index:%d offset:%"PRId64", ", pScanInfo->uid, *mapDataIndex, pBlockIter->block.aSubBlock[0].offset);
+#endif
+
+  return TSDB_CODE_SUCCESS;
+}
+
+static int32_t initBlockIterator(STsdbReader* pReader, SDataBlockIter* pBlockIter, int32_t numOfBlocks, SArray* pTableList) {
+  bool asc = ASCENDING_TRAVERSE(pReader->order);
+
+  SBlockOrderSupporter sup = {0};
+  pBlockIter->numOfBlocks = numOfBlocks;
+  taosArrayClear(pBlockIter->blockList);
+  pBlockIter->pTableMap = pReader->status.pTableMap;
+
+  // access data blocks according to the offset of each block in asc/desc order.
+  int32_t numOfTables = taosArrayGetSize(pTableList);
+
+  int64_t st = taosGetTimestampUs();
+  int32_t code = initBlockOrderSupporter(&sup, numOfTables);
+  if (code != TSDB_CODE_SUCCESS) {
+    return code;
+  }
+
+  int32_t cnt = 0;
+
+  for (int32_t i = 0; i < numOfTables; ++i) {
+    STableBlockScanInfo* pTableScanInfo = taosArrayGetP(pTableList, i);
+    ASSERT(pTableScanInfo->pBlockList != NULL && taosArrayGetSize(pTableScanInfo->pBlockList) > 0);
+
+    size_t num = taosArrayGetSize(pTableScanInfo->pBlockList);
+    sup.numOfBlocksPerTable[sup.numOfTables] = num;
+
+    char* buf = taosMemoryMalloc(sizeof(SBlockOrderWrapper) * num);
+    if (buf == NULL) {
+      cleanupBlockOrderSupporter(&sup);
+      return TSDB_CODE_OUT_OF_MEMORY;
+    }
+
+    sup.pDataBlockInfo[sup.numOfTables] = (SBlockOrderWrapper*)buf;
+
+    for (int32_t k = 0; k < num; ++k) {
+      SBlockIndex* pIndex = taosArrayGet(pTableScanInfo->pBlockList, k);
+      sup.pDataBlockInfo[sup.numOfTables][k] =
+          (SBlockOrderWrapper){.uid = pTableScanInfo->uid, .offset = pIndex->inFileOffset};
+      cnt++;
+    }
+
+    sup.numOfTables += 1;
+  }
+
+  if (numOfBlocks != cnt && sup.numOfTables != numOfTables) {
+    cleanupBlockOrderSupporter(&sup);
+    return TSDB_CODE_INVALID_PARA;
+  }
+
+  // since there is only one table qualified, blocks are not sorted
+  if (sup.numOfTables == 1) {
+    for (int32_t i = 0; i < numOfBlocks; ++i) {
+      SFileDataBlockInfo blockInfo = {.uid = sup.pDataBlockInfo[0][i].uid, .tbBlockIdx = i};
+      taosArrayPush(pBlockIter->blockList, &blockInfo);
+    }
+
+    int64_t et = taosGetTimestampUs();
+    tsdbDebug("%p create blocks info struct completed for one table, %d blocks not sorted, elapsed time:%.2f ms %s",
+              pReader, numOfBlocks, (et - st) / 1000.0, pReader->idStr);
+
+    pBlockIter->index = asc ? 0 : (numOfBlocks - 1);
+    cleanupBlockOrderSupporter(&sup);
+    doSetCurrentBlock(pBlockIter, pReader->idStr);
+    return TSDB_CODE_SUCCESS;
+  }
+
+  tsdbDebug("%p create data blocks info struct completed, %d blocks in %d tables %s", pReader, cnt, sup.numOfTables,
+            pReader->idStr);
+
+  SMultiwayMergeTreeInfo* pTree = NULL;
+
+  uint8_t ret = tMergeTreeCreate(&pTree, sup.numOfTables, &sup, fileDataBlockOrderCompar);
+  if (ret != TSDB_CODE_SUCCESS) {
+    cleanupBlockOrderSupporter(&sup);
+    return TSDB_CODE_OUT_OF_MEMORY;
+  }
+
+  int32_t numOfTotal = 0;
+  while (numOfTotal < cnt) {
+    int32_t pos = tMergeTreeGetChosenIndex(pTree);
+    int32_t index = sup.indexPerTable[pos]++;
+
+    SFileDataBlockInfo blockInfo = {.uid = sup.pDataBlockInfo[pos][index].uid, .tbBlockIdx = index};
+    taosArrayPush(pBlockIter->blockList, &blockInfo);
+
+    // set data block index overflow, in order to disable the offset comparator
+    if (sup.indexPerTable[pos] >= sup.numOfBlocksPerTable[pos]) {
+      sup.indexPerTable[pos] = sup.numOfBlocksPerTable[pos] + 1;
+    }
+
+    numOfTotal += 1;
+    tMergeTreeAdjust(pTree, tMergeTreeGetAdjustIndex(pTree));
+  }
+
+  int64_t et = taosGetTimestampUs();
+  tsdbDebug("%p %d data blocks access order completed, elapsed time:%.2f ms %s", pReader, numOfBlocks,
+            (et - st) / 1000.0, pReader->idStr);
+  cleanupBlockOrderSupporter(&sup);
+  taosMemoryFree(pTree);
+
+  pBlockIter->index = asc ? 0 : (numOfBlocks - 1);
+  doSetCurrentBlock(pBlockIter, pReader->idStr);
+
+  return TSDB_CODE_SUCCESS;
+}
+
+static bool blockIteratorNext(SDataBlockIter* pBlockIter, const char* idStr) {
+  bool asc = ASCENDING_TRAVERSE(pBlockIter->order);
+
+  int32_t step = asc ? 1 : -1;
+  if ((pBlockIter->index >= pBlockIter->numOfBlocks - 1 && asc) || (pBlockIter->index <= 0 && (!asc))) {
+    return false;
+  }
+
+  pBlockIter->index += step;
+  doSetCurrentBlock(pBlockIter, idStr);
+
+  return true;
+}
+
+/**
+ * This is an two rectangles overlap cases.
+ */
+static int32_t dataBlockPartiallyRequired(STimeWindow* pWindow, SVersionRange* pVerRange, SDataBlk* pBlock) {
+  return (pWindow->ekey < pBlock->maxKey.ts && pWindow->ekey >= pBlock->minKey.ts) ||
+         (pWindow->skey > pBlock->minKey.ts && pWindow->skey <= pBlock->maxKey.ts) ||
+         (pVerRange->minVer > pBlock->minVer && pVerRange->minVer <= pBlock->maxVer) ||
+         (pVerRange->maxVer < pBlock->maxVer && pVerRange->maxVer >= pBlock->minVer);
+}
+
+static bool getNeighborBlockOfSameTable(SFileDataBlockInfo* pBlockInfo, STableBlockScanInfo* pTableBlockScanInfo,
+                                        int32_t* nextIndex, int32_t order, SBlockIndex* pBlockIndex) {
+  bool asc = ASCENDING_TRAVERSE(order);
+  if (asc && pBlockInfo->tbBlockIdx >= taosArrayGetSize(pTableBlockScanInfo->pBlockList) - 1) {
+    return false;
+  }
+
+  if (!asc && pBlockInfo->tbBlockIdx == 0) {
+    return false;
+  }
+
+  int32_t step = asc ? 1 : -1;
+  *nextIndex = pBlockInfo->tbBlockIdx + step;
+  *pBlockIndex = *(SBlockIndex*)taosArrayGet(pTableBlockScanInfo->pBlockList, *nextIndex);
+  //  tMapDataGetItemByIdx(&pTableBlockScanInfo->mapData, pIndex->ordinalIndex, pBlock, tGetDataBlk);
+  return true;
+}
+
+static int32_t findFileBlockInfoIndex(SDataBlockIter* pBlockIter, SFileDataBlockInfo* pFBlockInfo) {
+  int32_t step = ASCENDING_TRAVERSE(pBlockIter->order) ? 1 : -1;
+  int32_t index = pBlockIter->index;
+
+  while (index < pBlockIter->numOfBlocks && index >= 0) {
+    SFileDataBlockInfo* pFBlock = taosArrayGet(pBlockIter->blockList, index);
+    if (pFBlock->uid == pFBlockInfo->uid && pFBlock->tbBlockIdx == pFBlockInfo->tbBlockIdx) {
+      return index;
+    }
+
+    index += step;
+  }
+
+  return -1;
+}
+
+static int32_t setFileBlockActiveInBlockIter(SDataBlockIter* pBlockIter, int32_t index, int32_t step) {
+  if (index < 0 || index >= pBlockIter->numOfBlocks) {
+    return -1;
+  }
+
+  SFileDataBlockInfo fblock = *(SFileDataBlockInfo*)taosArrayGet(pBlockIter->blockList, index);
+  pBlockIter->index += step;
+
+  if (index != pBlockIter->index) {
+    taosArrayRemove(pBlockIter->blockList, index);
+    taosArrayInsert(pBlockIter->blockList, pBlockIter->index, &fblock);
+
+    SFileDataBlockInfo* pBlockInfo = taosArrayGet(pBlockIter->blockList, pBlockIter->index);
+    ASSERT(pBlockInfo->uid == fblock.uid && pBlockInfo->tbBlockIdx == fblock.tbBlockIdx);
+  }
+
+  doSetCurrentBlock(pBlockIter, "");
+  return TSDB_CODE_SUCCESS;
+}
+
+// todo: this attribute could be acquired during extractin the global ordered block list.
+static bool overlapWithNeighborBlock(SDataBlk* pBlock, SBlockIndex* pNeighborBlockIndex, int32_t order) {
+  // it is the last block in current file, no chance to overlap with neighbor blocks.
+  if (ASCENDING_TRAVERSE(order)) {
+    return pBlock->maxKey.ts == pNeighborBlockIndex->window.skey;
+  } else {
+    return pBlock->minKey.ts == pNeighborBlockIndex->window.ekey;
+  }
+}
+
+static bool bufferDataInFileBlockGap(int32_t order, TSDBKEY key, SDataBlk* pBlock) {
+  bool ascScan = ASCENDING_TRAVERSE(order);
+
+  return (ascScan && (key.ts != TSKEY_INITIAL_VAL && key.ts <= pBlock->minKey.ts)) ||
+         (!ascScan && (key.ts != TSKEY_INITIAL_VAL && key.ts >= pBlock->maxKey.ts));
+}
+
+static bool keyOverlapFileBlock(TSDBKEY key, SDataBlk* pBlock, SVersionRange* pVerRange) {
+  return (key.ts >= pBlock->minKey.ts && key.ts <= pBlock->maxKey.ts) && (pBlock->maxVer >= pVerRange->minVer) &&
+         (pBlock->minVer <= pVerRange->maxVer);
+}
+
+static bool doCheckforDatablockOverlap(STableBlockScanInfo* pBlockScanInfo, const SDataBlk* pBlock,
+                                       int32_t startIndex) {
+  size_t num = taosArrayGetSize(pBlockScanInfo->delSkyline);
+
+  for (int32_t i = startIndex; i < num; i += 1) {
+    TSDBKEY* p = taosArrayGet(pBlockScanInfo->delSkyline, i);
+    if (p->ts >= pBlock->minKey.ts && p->ts <= pBlock->maxKey.ts) {
+      if (p->version >= pBlock->minVer) {
+        return true;
+      }
+    } else if (p->ts < pBlock->minKey.ts) {  // p->ts < pBlock->minKey.ts
+      if (p->version >= pBlock->minVer) {
+        if (i < num - 1) {
+          TSDBKEY* pnext = taosArrayGet(pBlockScanInfo->delSkyline, i + 1);
+          if (pnext->ts >= pBlock->minKey.ts) {
+            return true;
+          }
+        } else {  // it must be the last point
+          ASSERT(p->version == 0);
+        }
+      }
+    } else {  // (p->ts > pBlock->maxKey.ts) {
+      return false;
+    }
+  }
+
+  return false;
+}
+
+static bool overlapWithDelSkyline(STableBlockScanInfo* pBlockScanInfo, const SDataBlk* pBlock, int32_t order) {
+  if (pBlockScanInfo->delSkyline == NULL) {
+    return false;
+  }
+
+  // ts is not overlap
+  TSDBKEY* pFirst = taosArrayGet(pBlockScanInfo->delSkyline, 0);
+  TSDBKEY* pLast = taosArrayGetLast(pBlockScanInfo->delSkyline);
+  if (pBlock->minKey.ts > pLast->ts || pBlock->maxKey.ts < pFirst->ts) {
+    return false;
+  }
+
+  // version is not overlap
+  if (ASCENDING_TRAVERSE(order)) {
+    return doCheckforDatablockOverlap(pBlockScanInfo, pBlock, pBlockScanInfo->fileDelIndex);
+  } else {
+    int32_t index = pBlockScanInfo->fileDelIndex;
+    while (1) {
+      TSDBKEY* p = taosArrayGet(pBlockScanInfo->delSkyline, index);
+      if (p->ts > pBlock->minKey.ts && index > 0) {
+        index -= 1;
+      } else {  // find the first point that is smaller than the minKey.ts of dataBlock.
+        if (p->ts == pBlock->minKey.ts && p->version < pBlock->maxVer && index > 0) {
+          index -= 1;
+        }
+        break;
+      }
+    }
+
+    return doCheckforDatablockOverlap(pBlockScanInfo, pBlock, index);
+  }
+}
+
+typedef struct {
+  bool overlapWithNeighborBlock;
+  bool hasDupTs;
+  bool overlapWithDelInfo;
+  bool overlapWithLastBlock;
+  bool overlapWithKeyInBuf;
+  bool partiallyRequired;
+  bool moreThanCapcity;
+} SDataBlockToLoadInfo;
+
+static void getBlockToLoadInfo(SDataBlockToLoadInfo* pInfo, SFileDataBlockInfo* pBlockInfo, SDataBlk* pBlock,
+                               STableBlockScanInfo* pScanInfo, TSDBKEY keyInBuf, SLastBlockReader* pLastBlockReader,
+                               STsdbReader* pReader) {
+  int32_t     neighborIndex = 0;
+  SBlockIndex bIndex = {0};
+
+  bool hasNeighbor = getNeighborBlockOfSameTable(pBlockInfo, pScanInfo, &neighborIndex, pReader->order, &bIndex);
+
+  // overlap with neighbor
+  if (hasNeighbor) {
+    pInfo->overlapWithNeighborBlock = overlapWithNeighborBlock(pBlock, &bIndex, pReader->order);
+  }
+
+  // has duplicated ts of different version in this block
+  pInfo->hasDupTs = (pBlock->nSubBlock == 1) ? pBlock->hasDup : true;
+  pInfo->overlapWithDelInfo = overlapWithDelSkyline(pScanInfo, pBlock, pReader->order);
+
+  if (hasDataInLastBlock(pLastBlockReader)) {
+    int64_t tsLast = getCurrentKeyInLastBlock(pLastBlockReader);
+    pInfo->overlapWithLastBlock = !(pBlock->maxKey.ts < tsLast || pBlock->minKey.ts > tsLast);
+  }
+
+  pInfo->moreThanCapcity = pBlock->nRow > pReader->resBlockInfo.capacity;
+  pInfo->partiallyRequired = dataBlockPartiallyRequired(&pReader->window, &pReader->verRange, pBlock);
+  pInfo->overlapWithKeyInBuf = keyOverlapFileBlock(keyInBuf, pBlock, &pReader->verRange);
+}
+
+// 1. the version of all rows should be less than the endVersion
+// 2. current block should not overlap with next neighbor block
+// 3. current timestamp should not be overlap with each other
+// 4. output buffer should be large enough to hold all rows in current block
+// 5. delete info should not overlap with current block data
+// 6. current block should not contain the duplicated ts
+static bool fileBlockShouldLoad(STsdbReader* pReader, SFileDataBlockInfo* pBlockInfo, SDataBlk* pBlock,
+                                STableBlockScanInfo* pScanInfo, TSDBKEY keyInBuf, SLastBlockReader* pLastBlockReader) {
+  SDataBlockToLoadInfo info = {0};
+  getBlockToLoadInfo(&info, pBlockInfo, pBlock, pScanInfo, keyInBuf, pLastBlockReader, pReader);
+
+  bool loadDataBlock =
+      (info.overlapWithNeighborBlock || info.hasDupTs || info.partiallyRequired || info.overlapWithKeyInBuf ||
+       info.moreThanCapcity || info.overlapWithDelInfo || info.overlapWithLastBlock);
+
+  // log the reason why load the datablock for profile
+  if (loadDataBlock) {
+    tsdbDebug("%p uid:%" PRIu64
+                  " need to load the datablock, overlapneighbor:%d, hasDup:%d, partiallyRequired:%d, "
+                  "overlapWithKey:%d, greaterThanBuf:%d, overlapWithDel:%d, overlapWithlastBlock:%d, %s",
+              pReader, pBlockInfo->uid, info.overlapWithNeighborBlock, info.hasDupTs, info.partiallyRequired,
+              info.overlapWithKeyInBuf, info.moreThanCapcity, info.overlapWithDelInfo, info.overlapWithLastBlock,
+              pReader->idStr);
+  }
+
+  return loadDataBlock;
+}
+
+static bool isCleanFileDataBlock(STsdbReader* pReader, SFileDataBlockInfo* pBlockInfo, SDataBlk* pBlock,
+                                 STableBlockScanInfo* pScanInfo, TSDBKEY keyInBuf, SLastBlockReader* pLastBlockReader) {
+  SDataBlockToLoadInfo info = {0};
+  getBlockToLoadInfo(&info, pBlockInfo, pBlock, pScanInfo, keyInBuf, pLastBlockReader, pReader);
+  bool isCleanFileBlock = !(info.overlapWithNeighborBlock || info.hasDupTs || info.overlapWithKeyInBuf ||
+                            info.overlapWithDelInfo || info.overlapWithLastBlock);
+  return isCleanFileBlock;
+}
+
+static int32_t buildDataBlockFromBuf(STsdbReader* pReader, STableBlockScanInfo* pBlockScanInfo, int64_t endKey) {
+  if (!(pBlockScanInfo->iiter.hasVal || pBlockScanInfo->iter.hasVal)) {
+    return TSDB_CODE_SUCCESS;
+  }
+
+  SSDataBlock* pBlock = pReader->resBlockInfo.pResBlock;
+
+  int64_t st = taosGetTimestampUs();
+  int32_t code = buildDataBlockFromBufImpl(pBlockScanInfo, endKey, pReader->resBlockInfo.capacity, pReader);
+
+  blockDataUpdateTsWindow(pBlock, pReader->suppInfo.slotId[0]);
+  pBlock->info.id.uid = pBlockScanInfo->uid;
+
+  setComposedBlockFlag(pReader, true);
+
+  double elapsedTime = (taosGetTimestampUs() - st) / 1000.0;
+  tsdbDebug("%p build data block from cache completed, elapsed time:%.2f ms, numOfRows:%" PRId64 ", brange:%" PRId64
+                " - %" PRId64 ", uid:%" PRIu64 ",  %s",
+            pReader, elapsedTime, pBlock->info.rows, pBlock->info.window.skey, pBlock->info.window.ekey,
+            pBlockScanInfo->uid, pReader->idStr);
+
+  pReader->cost.buildmemBlock += elapsedTime;
+  return code;
+}
+
+static bool tryCopyDistinctRowFromFileBlock(STsdbReader* pReader, SBlockData* pBlockData, int64_t key,
+                                            SFileBlockDumpInfo* pDumpInfo, bool* copied) {
+  // opt version
+  // 1. it is not a border point
+  // 2. the direct next point is not an duplicated timestamp
+  int32_t code = TSDB_CODE_SUCCESS;
+
+  *copied = false;
+  bool asc = (pReader->order == TSDB_ORDER_ASC);
+  if ((pDumpInfo->rowIndex < pDumpInfo->totalRows - 1 && asc) || (pDumpInfo->rowIndex > 0 && (!asc))) {
+    int32_t step = pReader->order == TSDB_ORDER_ASC ? 1 : -1;
+
+    int64_t nextKey = pBlockData->aTSKEY[pDumpInfo->rowIndex + step];
+    if (nextKey != key) {  // merge is not needed
+      code = doAppendRowFromFileBlock(pReader->resBlockInfo.pResBlock, pReader, pBlockData, pDumpInfo->rowIndex);
+      if (code) {
+        return code;
+      }
+      pDumpInfo->rowIndex += step;
+      *copied = true;
+    }
+  }
+
+  return code;
+}
+
+static bool nextRowFromLastBlocks(SLastBlockReader* pLastBlockReader, STableBlockScanInfo* pScanInfo,
+                                  SVersionRange* pVerRange) {
+  int32_t step = ASCENDING_TRAVERSE(pLastBlockReader->order) ? 1 : -1;
+
+  while (1) {
+    bool hasVal = tMergeTreeNext(&pLastBlockReader->mergeTree);
+    if (!hasVal) {  // the next value will be the accessed key in stt
+      pScanInfo->lastKeyInStt += step;
+      return false;
+    }
+
+    TSDBROW* pRow = tMergeTreeGetRow(&pLastBlockReader->mergeTree);
+    int64_t key = pRow->pBlockData->aTSKEY[pRow->iRow];
+    int64_t ver = pRow->pBlockData->aVersion[pRow->iRow];
+
+    pLastBlockReader->currentKey = key;
+    pScanInfo->lastKeyInStt = key;
+
+    if (!hasBeenDropped(pScanInfo->delSkyline, &pScanInfo->lastBlockDelIndex, key, ver, pLastBlockReader->order, pVerRange)) {
+      return true;
+    }
+  }
+}
+
+static bool tryCopyDistinctRowFromSttBlock(TSDBROW* fRow, SLastBlockReader* pLastBlockReader,
+                                           STableBlockScanInfo* pScanInfo, int64_t ts, STsdbReader* pReader,
+                                           bool* copied) {
+  int32_t code = TSDB_CODE_SUCCESS;
+
+  *copied = false;
+
+  bool hasVal = nextRowFromLastBlocks(pLastBlockReader, pScanInfo, &pReader->verRange);
+  if (hasVal) {
+    int64_t next1 = getCurrentKeyInLastBlock(pLastBlockReader);
+    if (next1 != ts) {
+      code = doAppendRowFromFileBlock(pReader->resBlockInfo.pResBlock, pReader, fRow->pBlockData, fRow->iRow);
+      if (code) {
+        return code;
+      }
+
+      *copied = true;
+      return code;
+    }
+  } else {
+    code = doAppendRowFromFileBlock(pReader->resBlockInfo.pResBlock, pReader, fRow->pBlockData, fRow->iRow);
+    if (code) {
+      return code;
+    }
+
+    *copied = true;
+    return code;
+  }
+
+  return code;
+}
+
+static FORCE_INLINE STSchema* doGetSchemaForTSRow(int32_t sversion, STsdbReader* pReader, uint64_t uid) {
+  // always set the newest schema version in pReader->pSchema
+  if (pReader->pSchema == NULL) {
+    STSchema* ps = getTableSchemaImpl(pReader, uid);
+    if (ps == NULL) {
+      return NULL;
+    }
+  }
+
+  if (pReader->pSchema && sversion == pReader->pSchema->version) {
+    return pReader->pSchema;
+  }
+
+  void** p = tSimpleHashGet(pReader->pSchemaMap, &sversion, sizeof(sversion));
+  if (p != NULL) {
+    return *(STSchema**)p;
+  }
+
+  STSchema* ptr = NULL;
+  int32_t code = metaGetTbTSchemaEx(pReader->pTsdb->pVnode->pMeta, pReader->suid, uid, sversion, &ptr);
+  if (code != TSDB_CODE_SUCCESS) {
+    terrno = code;
+    return NULL;
+  } else {
+    code = tSimpleHashPut(pReader->pSchemaMap, &sversion, sizeof(sversion), &ptr, POINTER_BYTES);
+    if (code != TSDB_CODE_SUCCESS) {
+      terrno = code;
+      return NULL;
+    }
+    return ptr;
+  }
+}
+
+static int32_t doMergeBufAndFileRows(STsdbReader* pReader, STableBlockScanInfo* pBlockScanInfo, TSDBROW* pRow,
+                                     SIterInfo* pIter, int64_t key, SLastBlockReader* pLastBlockReader) {
+  SRowMerger*         pMerger = &pReader->status.merger;
+  SRow*               pTSRow = NULL;
+  SBlockData*         pBlockData = &pReader->status.fileBlockData;
+  SFileBlockDumpInfo* pDumpInfo = &pReader->status.fBlockDumpInfo;
+
+  int64_t tsLast = INT64_MIN;
+  if (hasDataInLastBlock(pLastBlockReader)) {
+    tsLast = getCurrentKeyInLastBlock(pLastBlockReader);
+  }
+
+  TSDBKEY k = TSDBROW_KEY(pRow);
+  TSDBROW fRow = tsdbRowFromBlockData(pBlockData, pDumpInfo->rowIndex);
+
+  // merge is not initialized yet, due to the fact that the pReader->pSchema is not initialized
+  if (pMerger->pArray == NULL) {
+    ASSERT(pReader->pSchema == NULL);
+    STSchema* ps = getTableSchemaImpl(pReader, pBlockScanInfo->uid);
+    if (ps == NULL) {
+      return terrno;
+    }
+  }
+
+  int64_t minKey = 0;
+  if (pReader->order == TSDB_ORDER_ASC) {
+    minKey = INT64_MAX;  // chosen the minimum value
+    if (minKey > tsLast && hasDataInLastBlock(pLastBlockReader)) {
+      minKey = tsLast;
+    }
+
+    if (minKey > k.ts) {
+      minKey = k.ts;
+    }
+
+    if (minKey > key && hasDataInFileBlock(pBlockData, pDumpInfo)) {
+      minKey = key;
+    }
+  } else {
+    minKey = INT64_MIN;
+    if (minKey < tsLast && hasDataInLastBlock(pLastBlockReader)) {
+      minKey = tsLast;
+    }
+
+    if (minKey < k.ts) {
+      minKey = k.ts;
+    }
+
+    if (minKey < key && hasDataInFileBlock(pBlockData, pDumpInfo)) {
+      minKey = key;
+    }
+  }
+
+  // todo remove init
+  bool init = false;
+
+  // ASC: file block ---> last block -----> imem -----> mem
+  // DESC: mem -----> imem -----> last block -----> file block
+  if (pReader->order == TSDB_ORDER_ASC) {
+    if (minKey == key) {
+      init = true;
+      int32_t code = tsdbRowMergerAdd(pMerger, &fRow, pReader->pSchema);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+      doMergeRowsInFileBlocks(pBlockData, pBlockScanInfo, pReader);
+    }
+
+    if (minKey == tsLast) {
+      TSDBROW* fRow1 = tMergeTreeGetRow(&pLastBlockReader->mergeTree);
+      if (init) {
+        tsdbRowMergerAdd(pMerger, fRow1, NULL);
+      } else {
+        init = true;
+        int32_t code = tsdbRowMergerAdd(pMerger, fRow1, pReader->pSchema);
+        if (code != TSDB_CODE_SUCCESS) {
+          return code;
+        }
+      }
+      doMergeRowsInLastBlock(pLastBlockReader, pBlockScanInfo, tsLast, pMerger, &pReader->verRange, pReader->idStr);
+    }
+
+    if (minKey == k.ts) {
+      STSchema* pSchema = doGetSchemaForTSRow(TSDBROW_SVERSION(pRow), pReader, pBlockScanInfo->uid);
+      if (pSchema == NULL) {
+        return terrno;
+      }
+      if (init) {
+        tsdbRowMergerAdd(pMerger, pRow, pSchema);
+      } else {
+        init = true;
+        int32_t code = tsdbRowMergerAdd(pMerger, pRow, pSchema);
+        if (code != TSDB_CODE_SUCCESS) {
+          return code;
+        }
+      }
+      int32_t code = doMergeRowsInBuf(pIter, pBlockScanInfo->uid, k.ts, pBlockScanInfo->delSkyline, pReader);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+    }
+  } else {
+    if (minKey == k.ts) {
+      init = true;
+      STSchema* pSchema = doGetSchemaForTSRow(TSDBROW_SVERSION(pRow), pReader, pBlockScanInfo->uid);
+      if (pSchema == NULL) {
+        return terrno;
+      }
+
+      int32_t   code = tsdbRowMergerAdd(pMerger, pRow, pSchema);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+
+      code = doMergeRowsInBuf(pIter, pBlockScanInfo->uid, k.ts, pBlockScanInfo->delSkyline, pReader);
+      if (code != TSDB_CODE_SUCCESS || pMerger->pTSchema == NULL) {
+        return code;
+      }
+    }
+
+    if (minKey == tsLast) {
+      TSDBROW* fRow1 = tMergeTreeGetRow(&pLastBlockReader->mergeTree);
+      if (init) {
+        tsdbRowMergerAdd(pMerger, fRow1, NULL);
+      } else {
+        init = true;
+        int32_t code = tsdbRowMergerAdd(pMerger, fRow1, pReader->pSchema);
+        if (code != TSDB_CODE_SUCCESS) {
+          return code;
+        }
+      }
+      doMergeRowsInLastBlock(pLastBlockReader, pBlockScanInfo, tsLast, pMerger, &pReader->verRange, pReader->idStr);
+    }
+
+    if (minKey == key) {
+      if (init) {
+        tsdbRowMergerAdd(pMerger, &fRow, NULL);
+      } else {
+        init = true;
+        int32_t code = tsdbRowMergerAdd(pMerger, &fRow, pReader->pSchema);
+        if (code != TSDB_CODE_SUCCESS) {
+          return code;
+        }
+      }
+      doMergeRowsInFileBlocks(pBlockData, pBlockScanInfo, pReader);
+    }
+  }
+
+  int32_t code = tsdbRowMergerGetRow(pMerger, &pTSRow);
+  if (code != TSDB_CODE_SUCCESS) {
+    return code;
+  }
+
+  code = doAppendRowFromTSRow(pReader->resBlockInfo.pResBlock, pReader, pTSRow, pBlockScanInfo);
+
+  taosMemoryFree(pTSRow);
+  tsdbRowMergerClear(pMerger);
+
+  return code;
+}
+
+static int32_t doMergeFileBlockAndLastBlock(SLastBlockReader* pLastBlockReader, STsdbReader* pReader,
+                                            STableBlockScanInfo* pBlockScanInfo, SBlockData* pBlockData,
+                                            bool mergeBlockData) {
+  SRowMerger* pMerger = &pReader->status.merger;
+  SFileBlockDumpInfo* pDumpInfo = &pReader->status.fBlockDumpInfo;
+
+  int64_t  tsLastBlock = getCurrentKeyInLastBlock(pLastBlockReader);
+  bool     copied = false;
+  int32_t  code = TSDB_CODE_SUCCESS;
+  SRow*    pTSRow = NULL;
+  TSDBROW* pRow = tMergeTreeGetRow(&pLastBlockReader->mergeTree);
+
+  // create local variable to hold the row value
+  TSDBROW  fRow = {.iRow = pRow->iRow, .type = TSDBROW_COL_FMT, .pBlockData = pRow->pBlockData};
+
+  tsdbTrace("fRow ptr:%p, %d, uid:%" PRIu64 ", %s", pRow->pBlockData, pRow->iRow, pLastBlockReader->uid, pReader->idStr);
+
+  // only last block exists
+  if ((!mergeBlockData) || (tsLastBlock != pBlockData->aTSKEY[pDumpInfo->rowIndex])) {
+    code = tryCopyDistinctRowFromSttBlock(&fRow, pLastBlockReader, pBlockScanInfo, tsLastBlock, pReader, &copied);
+    if (code) {
+      return code;
+    }
+
+    if (copied) {
+      pBlockScanInfo->lastKey = tsLastBlock;
+      return TSDB_CODE_SUCCESS;
+    } else {
+      code = tsdbRowMergerAdd(pMerger, &fRow, pReader->pSchema);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+
+      TSDBROW* pRow1 = tMergeTreeGetRow(&pLastBlockReader->mergeTree);
+      tsdbRowMergerAdd(pMerger, pRow1, NULL);
+      doMergeRowsInLastBlock(pLastBlockReader, pBlockScanInfo, tsLastBlock, pMerger, &pReader->verRange, pReader->idStr);
+
+      code = tsdbRowMergerGetRow(pMerger, &pTSRow);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+
+      code = doAppendRowFromTSRow(pReader->resBlockInfo.pResBlock, pReader, pTSRow, pBlockScanInfo);
+
+      taosMemoryFree(pTSRow);
+      tsdbRowMergerClear(pMerger);
+
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+    }
+  } else {  // not merge block data
+    code = tsdbRowMergerAdd(pMerger, &fRow, pReader->pSchema);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    doMergeRowsInLastBlock(pLastBlockReader, pBlockScanInfo, tsLastBlock, pMerger, &pReader->verRange, pReader->idStr);
+
+    // merge with block data if ts == key
+    if (tsLastBlock == pBlockData->aTSKEY[pDumpInfo->rowIndex]) {
+      doMergeRowsInFileBlocks(pBlockData, pBlockScanInfo, pReader);
+    }
+
+    code = tsdbRowMergerGetRow(pMerger, &pTSRow);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    code = doAppendRowFromTSRow(pReader->resBlockInfo.pResBlock, pReader, pTSRow, pBlockScanInfo);
+
+    taosMemoryFree(pTSRow);
+    tsdbRowMergerClear(pMerger);
+
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+  }
+
+  return TSDB_CODE_SUCCESS;
+}
+
+static int32_t mergeFileBlockAndLastBlock(STsdbReader* pReader, SLastBlockReader* pLastBlockReader, int64_t key,
+                                          STableBlockScanInfo* pBlockScanInfo, SBlockData* pBlockData) {
+  SFileBlockDumpInfo* pDumpInfo = &pReader->status.fBlockDumpInfo;
+  SRowMerger* pMerger = &pReader->status.merger;
+
+  // merge is not initialized yet, due to the fact that the pReader->pSchema is not initialized
+  if (pMerger->pArray == NULL) {
+    ASSERT(pReader->pSchema == NULL);
+    STSchema* ps = getTableSchemaImpl(pReader, pBlockScanInfo->uid);
+    if (ps == NULL) {
+      return terrno;
+    }
+  }
+
+  if (hasDataInFileBlock(pBlockData, pDumpInfo)) {
+    // no last block available, only data block exists
+    if (!hasDataInLastBlock(pLastBlockReader)) {
+      return mergeRowsInFileBlocks(pBlockData, pBlockScanInfo, key, pReader);
+    }
+
+    // row in last file block
+    TSDBROW fRow = tsdbRowFromBlockData(pBlockData, pDumpInfo->rowIndex);
+    int64_t ts = getCurrentKeyInLastBlock(pLastBlockReader);
+    ASSERT(ts >= key);
+
+    if (ASCENDING_TRAVERSE(pReader->order)) {
+      if (key < ts) {  // imem, mem are all empty, file blocks (data blocks and last block) exist
+        return mergeRowsInFileBlocks(pBlockData, pBlockScanInfo, key, pReader);
+      } else if (key == ts) {
+        SRow*       pTSRow = NULL;
+        int32_t code = tsdbRowMergerAdd(pMerger, &fRow, pReader->pSchema);
+        if (code != TSDB_CODE_SUCCESS) {
+          return code;
+        }
+
+        doMergeRowsInFileBlocks(pBlockData, pBlockScanInfo, pReader);
+
+        TSDBROW* pRow1 = tMergeTreeGetRow(&pLastBlockReader->mergeTree);
+        tsdbRowMergerAdd(pMerger, pRow1, NULL);
+
+        doMergeRowsInLastBlock(pLastBlockReader, pBlockScanInfo, ts, pMerger, &pReader->verRange, pReader->idStr);
+
+        code = tsdbRowMergerGetRow(pMerger, &pTSRow);
+        if (code != TSDB_CODE_SUCCESS) {
+          return code;
+        }
+
+        code = doAppendRowFromTSRow(pReader->resBlockInfo.pResBlock, pReader, pTSRow, pBlockScanInfo);
+
+        taosMemoryFree(pTSRow);
+        tsdbRowMergerClear(pMerger);
+        return code;
+      } else {
+        return TSDB_CODE_SUCCESS;
+      }
+    } else {  // desc order
+      return doMergeFileBlockAndLastBlock(pLastBlockReader, pReader, pBlockScanInfo, pBlockData, true);
+    }
+  } else {  // only last block exists
+    return doMergeFileBlockAndLastBlock(pLastBlockReader, pReader, pBlockScanInfo, NULL, false);
+  }
+}
+
+static int32_t doMergeMultiLevelRows(STsdbReader* pReader, STableBlockScanInfo* pBlockScanInfo, SBlockData* pBlockData,
+                                     SLastBlockReader* pLastBlockReader) {
+  SRowMerger*         pMerger = &pReader->status.merger;
+  SRow*               pTSRow = NULL;
+  int32_t             code = TSDB_CODE_SUCCESS;
+  SFileBlockDumpInfo* pDumpInfo = &pReader->status.fBlockDumpInfo;
+  SArray*             pDelList = pBlockScanInfo->delSkyline;
+
+  TSDBROW* pRow = getValidMemRow(&pBlockScanInfo->iter, pDelList, pReader);
+  TSDBROW* piRow = getValidMemRow(&pBlockScanInfo->iiter, pDelList, pReader);
+
+  int64_t tsLast = INT64_MIN;
+  if (hasDataInLastBlock(pLastBlockReader)) {
+    tsLast = getCurrentKeyInLastBlock(pLastBlockReader);
+  }
+
+  int64_t key = hasDataInFileBlock(pBlockData, pDumpInfo) ? pBlockData->aTSKEY[pDumpInfo->rowIndex] : INT64_MIN;
+
+  TSDBKEY   k = TSDBROW_KEY(pRow);
+  TSDBKEY   ik = TSDBROW_KEY(piRow);
+  STSchema* pSchema = doGetSchemaForTSRow(TSDBROW_SVERSION(pRow), pReader, pBlockScanInfo->uid);
+  if (pSchema == NULL) {
+    return code;
+  }
+
+  STSchema* piSchema = doGetSchemaForTSRow(TSDBROW_SVERSION(piRow), pReader, pBlockScanInfo->uid);
+  if (piSchema == NULL) {
+    return code;
+  }
+
+  // merge is not initialized yet, due to the fact that the pReader->pSchema is not initialized
+  if (pMerger->pArray == NULL) {
+    ASSERT(pReader->pSchema == NULL);
+    STSchema* ps = getTableSchemaImpl(pReader, pBlockScanInfo->uid);
+    if (ps == NULL) {
+      return terrno;
+    }
+  }
+
+  int64_t minKey = 0;
+  if (ASCENDING_TRAVERSE(pReader->order)) {
+    minKey = INT64_MAX;  // let's find the minimum
+    if (minKey > k.ts) {
+      minKey = k.ts;
+    }
+
+    if (minKey > ik.ts) {
+      minKey = ik.ts;
+    }
+
+    if (minKey > key && hasDataInFileBlock(pBlockData, pDumpInfo)) {
+      minKey = key;
+    }
+
+    if (minKey > tsLast && hasDataInLastBlock(pLastBlockReader)) {
+      minKey = tsLast;
+    }
+  } else {
+    minKey = INT64_MIN;  // let find the maximum ts value
+    if (minKey < k.ts) {
+      minKey = k.ts;
+    }
+
+    if (minKey < ik.ts) {
+      minKey = ik.ts;
+    }
+
+    if (minKey < key && hasDataInFileBlock(pBlockData, pDumpInfo)) {
+      minKey = key;
+    }
+
+    if (minKey < tsLast && hasDataInLastBlock(pLastBlockReader)) {
+      minKey = tsLast;
+    }
+  }
+
+  bool init = false;
+
+  // ASC: file block -----> last block -----> imem -----> mem
+  // DESC: mem -----> imem -----> last block -----> file block
+  if (ASCENDING_TRAVERSE(pReader->order)) {
+    if (minKey == key) {
+      init = true;
+      TSDBROW fRow = tsdbRowFromBlockData(pBlockData, pDumpInfo->rowIndex);
+      code = tsdbRowMergerAdd(pMerger, &fRow, pReader->pSchema);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+
+      doMergeRowsInFileBlocks(pBlockData, pBlockScanInfo, pReader);
+    }
+
+    if (minKey == tsLast) {
+      TSDBROW* pRow1 = tMergeTreeGetRow(&pLastBlockReader->mergeTree);
+      if (init) {
+        tsdbRowMergerAdd(pMerger, pRow1, NULL);
+      } else {
+        init = true;
+        code = tsdbRowMergerAdd(pMerger, pRow1, pReader->pSchema);
+        if (code != TSDB_CODE_SUCCESS) {
+          return code;
+        }
+      }
+
+      doMergeRowsInLastBlock(pLastBlockReader, pBlockScanInfo, tsLast, pMerger, &pReader->verRange, pReader->idStr);
+    }
+
+    if (minKey == ik.ts) {
+      if (init) {
+        tsdbRowMergerAdd(pMerger, piRow, piSchema);
+      } else {
+        init = true;
+        code = tsdbRowMergerAdd(pMerger, piRow, piSchema);
+        if (code != TSDB_CODE_SUCCESS) {
+          return code;
+        }
+      }
+
+      code = doMergeRowsInBuf(&pBlockScanInfo->iiter, pBlockScanInfo->uid, ik.ts, pBlockScanInfo->delSkyline, pReader);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+    }
+
+    if (minKey == k.ts) {
+      if (init) {
+        tsdbRowMergerAdd(pMerger, pRow, pSchema);
+      } else {
+        // STSchema* pSchema = doGetSchemaForTSRow(TSDBROW_SVERSION(pRow), pReader, pBlockScanInfo->uid);
+        code = tsdbRowMergerAdd(pMerger, pRow, pSchema);
+        if (code != TSDB_CODE_SUCCESS) {
+          return code;
+        }
+      }
+      code = doMergeRowsInBuf(&pBlockScanInfo->iter, pBlockScanInfo->uid, k.ts, pBlockScanInfo->delSkyline, pReader);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+    }
+  } else {
+    if (minKey == k.ts) {
+      init = true;
+      code = tsdbRowMergerAdd(pMerger, pRow, pSchema);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+
+      code = doMergeRowsInBuf(&pBlockScanInfo->iter, pBlockScanInfo->uid, k.ts, pBlockScanInfo->delSkyline, pReader);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+    }
+
+    if (minKey == ik.ts) {
+      if (init) {
+        tsdbRowMergerAdd(pMerger, piRow, piSchema);
+      } else {
+        init = true;
+        code = tsdbRowMergerAdd(pMerger, piRow, piSchema);
+        if (code != TSDB_CODE_SUCCESS) {
+          return code;
+        }
+      }
+      code = doMergeRowsInBuf(&pBlockScanInfo->iiter, pBlockScanInfo->uid, ik.ts, pBlockScanInfo->delSkyline, pReader);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+    }
+
+    if (minKey == tsLast) {
+      TSDBROW* pRow1 = tMergeTreeGetRow(&pLastBlockReader->mergeTree);
+      if (init) {
+        tsdbRowMergerAdd(pMerger, pRow1, NULL);
+      } else {
+        init = true;
+        code = tsdbRowMergerAdd(pMerger, pRow1, pReader->pSchema);
+        if (code != TSDB_CODE_SUCCESS) {
+          return code;
+        }
+      }
+      doMergeRowsInLastBlock(pLastBlockReader, pBlockScanInfo, tsLast, pMerger, &pReader->verRange, pReader->idStr);
+    }
+
+    if (minKey == key) {
+      TSDBROW fRow = tsdbRowFromBlockData(pBlockData, pDumpInfo->rowIndex);
+      if (!init) {
+        code = tsdbRowMergerAdd(pMerger, &fRow, pReader->pSchema);
+        if (code != TSDB_CODE_SUCCESS) {
+          return code;
+        }
+      } else {
+        tsdbRowMergerAdd(pMerger, &fRow, NULL);
+      }
+      doMergeRowsInFileBlocks(pBlockData, pBlockScanInfo, pReader);
+    }
+  }
+
+  code = tsdbRowMergerGetRow(pMerger, &pTSRow);
+  if (code != TSDB_CODE_SUCCESS) {
+    return code;
+  }
+
+  code = doAppendRowFromTSRow(pReader->resBlockInfo.pResBlock, pReader, pTSRow, pBlockScanInfo);
+
+  taosMemoryFree(pTSRow);
+  tsdbRowMergerClear(pMerger);
+  return code;
+}
+
+static int32_t initMemDataIterator(STableBlockScanInfo* pBlockScanInfo, STsdbReader* pReader) {
+  if (pBlockScanInfo->iterInit) {
+    return TSDB_CODE_SUCCESS;
+  }
+
+  int32_t code = TSDB_CODE_SUCCESS;
+
+  TSDBKEY startKey = {0};
+  if (ASCENDING_TRAVERSE(pReader->order)) {
+    // startKey = (TSDBKEY){.ts = pReader->window.skey, .version = pReader->verRange.minVer};
+    startKey = (TSDBKEY){.ts = pBlockScanInfo->lastKey + 1, .version = pReader->verRange.minVer};
+  } else {
+    // startKey = (TSDBKEY){.ts = pReader->window.ekey, .version = pReader->verRange.maxVer};
+    startKey = (TSDBKEY){.ts = pBlockScanInfo->lastKey - 1, .version = pReader->verRange.maxVer};
+  }
+
+  int32_t backward = (!ASCENDING_TRAVERSE(pReader->order));
+  int64_t st = 0;
+
+  STbData* d = NULL;
+  if (pReader->pReadSnap->pMem != NULL) {
+    d = tsdbGetTbDataFromMemTable(pReader->pReadSnap->pMem, pReader->suid, pBlockScanInfo->uid);
+    if (d != NULL) {
+      code = tsdbTbDataIterCreate(d, &startKey, backward, &pBlockScanInfo->iter.iter);
+      if (code == TSDB_CODE_SUCCESS) {
+        pBlockScanInfo->iter.hasVal = (tsdbTbDataIterGet(pBlockScanInfo->iter.iter) != NULL);
+
+        tsdbDebug("%p uid:%" PRIu64 ", check data in mem from skey:%" PRId64 ", order:%d, ts range in buf:%" PRId64
+                      "-%" PRId64 " %s",
+                  pReader, pBlockScanInfo->uid, startKey.ts, pReader->order, d->minKey, d->maxKey, pReader->idStr);
+      } else {
+        tsdbError("%p uid:%" PRIu64 ", failed to create iterator for imem, code:%s, %s", pReader, pBlockScanInfo->uid,
+                  tstrerror(code), pReader->idStr);
+        return code;
+      }
+    }
+  } else {
+    tsdbDebug("%p uid:%" PRIu64 ", no data in mem, %s", pReader, pBlockScanInfo->uid, pReader->idStr);
+  }
+
+  STbData* di = NULL;
+  if (pReader->pReadSnap->pIMem != NULL) {
+    di = tsdbGetTbDataFromMemTable(pReader->pReadSnap->pIMem, pReader->suid, pBlockScanInfo->uid);
+    if (di != NULL) {
+      code = tsdbTbDataIterCreate(di, &startKey, backward, &pBlockScanInfo->iiter.iter);
+      if (code == TSDB_CODE_SUCCESS) {
+        pBlockScanInfo->iiter.hasVal = (tsdbTbDataIterGet(pBlockScanInfo->iiter.iter) != NULL);
+
+        tsdbDebug("%p uid:%" PRIu64 ", check data in imem from skey:%" PRId64 ", order:%d, ts range in buf:%" PRId64
+                      "-%" PRId64 " %s",
+                  pReader, pBlockScanInfo->uid, startKey.ts, pReader->order, di->minKey, di->maxKey, pReader->idStr);
+      } else {
+        tsdbError("%p uid:%" PRIu64 ", failed to create iterator for mem, code:%s, %s", pReader, pBlockScanInfo->uid,
+                  tstrerror(code), pReader->idStr);
+        return code;
+      }
+    }
+  } else {
+    tsdbDebug("%p uid:%" PRIu64 ", no data in imem, %s", pReader, pBlockScanInfo->uid, pReader->idStr);
+  }
+
+  st = taosGetTimestampUs();
+  initDelSkylineIterator(pBlockScanInfo, pReader, d, di);
+  pReader->cost.initDelSkylineIterTime += (taosGetTimestampUs() - st) / 1000.0;
+
+  pBlockScanInfo->iterInit = true;
+  return TSDB_CODE_SUCCESS;
+}
+
+static bool isValidFileBlockRow(SBlockData* pBlockData, SFileBlockDumpInfo* pDumpInfo,
+                                STableBlockScanInfo* pBlockScanInfo, STsdbReader* pReader) {
+  // it is an multi-table data block
+  if (pBlockData->aUid != NULL) {
+    uint64_t uid = pBlockData->aUid[pDumpInfo->rowIndex];
+    if (uid != pBlockScanInfo->uid) {  // move to next row
+      return false;
+    }
+  }
+
+  // check for version and time range
+  int64_t ver = pBlockData->aVersion[pDumpInfo->rowIndex];
+  if (ver > pReader->verRange.maxVer || ver < pReader->verRange.minVer) {
+    return false;
+  }
+
+  int64_t ts = pBlockData->aTSKEY[pDumpInfo->rowIndex];
+  if (ts > pReader->window.ekey || ts < pReader->window.skey) {
+    return false;
+  }
+
+  if (hasBeenDropped(pBlockScanInfo->delSkyline, &pBlockScanInfo->fileDelIndex, ts, ver, pReader->order,
+                     &pReader->verRange)) {
+    return false;
+  }
+
+  return true;
+}
+
+static bool initLastBlockReader(SLastBlockReader* pLBlockReader, STableBlockScanInfo* pScanInfo, STsdbReader* pReader) {
+  // the last block reader has been initialized for this table.
+  if (pLBlockReader->uid == pScanInfo->uid) {
+    return hasDataInLastBlock(pLBlockReader);
+  }
+
+  if (pLBlockReader->uid != 0) {
+    tMergeTreeClose(&pLBlockReader->mergeTree);
+  }
+
+  initMemDataIterator(pScanInfo, pReader);
+  pLBlockReader->uid = pScanInfo->uid;
+
+  STimeWindow w = pLBlockReader->window;
+  if (ASCENDING_TRAVERSE(pLBlockReader->order)) {
+    w.skey = pScanInfo->lastKeyInStt;
+  } else {
+    w.ekey = pScanInfo->lastKeyInStt;
+  }
+
+  tsdbDebug("init last block reader, window:%" PRId64 "-%" PRId64 ", uid:%" PRIu64 ", %s", w.skey, w.ekey,
+            pScanInfo->uid, pReader->idStr);
+  int32_t code = tMergeTreeOpen(&pLBlockReader->mergeTree, (pLBlockReader->order == TSDB_ORDER_DESC),
+                                pReader->pFileReader, pReader->suid, pScanInfo->uid, &w, &pLBlockReader->verRange,
+                                pLBlockReader->pInfo, false, pReader->idStr, false, pReader->status.pLDataIter);
+  if (code != TSDB_CODE_SUCCESS) {
+    return false;
+  }
+
+  return nextRowFromLastBlocks(pLBlockReader, pScanInfo, &pReader->verRange);
+}
+
+static bool hasDataInLastBlock(SLastBlockReader* pLastBlockReader) { return pLastBlockReader->mergeTree.pIter != NULL; }
+
+bool hasDataInFileBlock(const SBlockData* pBlockData, const SFileBlockDumpInfo* pDumpInfo) {
+  if ((pBlockData->nRow > 0) && (pBlockData->nRow != pDumpInfo->totalRows)) {
+    return false;  // this is an invalid result.
+  }
+  return pBlockData->nRow > 0 && (!pDumpInfo->allDumped);
+}
+
+int32_t mergeRowsInFileBlocks(SBlockData* pBlockData, STableBlockScanInfo* pBlockScanInfo, int64_t key,
+                              STsdbReader* pReader) {
+  SRowMerger*         pMerger = &pReader->status.merger;
+  SFileBlockDumpInfo* pDumpInfo = &pReader->status.fBlockDumpInfo;
+  bool                copied = false;
+  int32_t             code = tryCopyDistinctRowFromFileBlock(pReader, pBlockData, key, pDumpInfo, &copied);
+  if (code) {
+    return code;
+  }
+
+  // merge is not initialized yet, due to the fact that the pReader->pSchema is not initialized
+  if (pMerger->pArray == NULL) {
+    ASSERT(pReader->pSchema == NULL);
+    STSchema* ps = getTableSchemaImpl(pReader, pBlockScanInfo->uid);
+    if (ps == NULL) {
+      return terrno;
+    }
+  }
+
+  if (copied) {
+    pBlockScanInfo->lastKey = key;
+    return TSDB_CODE_SUCCESS;
+  } else {
+    TSDBROW fRow = tsdbRowFromBlockData(pBlockData, pDumpInfo->rowIndex);
+
+    SRow*      pTSRow = NULL;
+    code = tsdbRowMergerAdd(pMerger, &fRow, pReader->pSchema);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    doMergeRowsInFileBlocks(pBlockData, pBlockScanInfo, pReader);
+    code = tsdbRowMergerGetRow(pMerger, &pTSRow);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    code = doAppendRowFromTSRow(pReader->resBlockInfo.pResBlock, pReader, pTSRow, pBlockScanInfo);
+
+    taosMemoryFree(pTSRow);
+    tsdbRowMergerClear(pMerger);
+    return code;
+  }
+}
+
+static int32_t buildComposedDataBlockImpl(STsdbReader* pReader, STableBlockScanInfo* pBlockScanInfo,
+                                          SBlockData* pBlockData, SLastBlockReader* pLastBlockReader) {
+  SFileBlockDumpInfo* pDumpInfo = &pReader->status.fBlockDumpInfo;
+
+  TSDBROW *pRow = NULL, *piRow = NULL;
+  int64_t key = (pBlockData->nRow > 0 && (!pDumpInfo->allDumped)) ? pBlockData->aTSKEY[pDumpInfo->rowIndex] : INT64_MIN;
+  if (pBlockScanInfo->iter.hasVal) {
+    pRow = getValidMemRow(&pBlockScanInfo->iter, pBlockScanInfo->delSkyline, pReader);
+  }
+
+  if (pBlockScanInfo->iiter.hasVal) {
+    piRow = getValidMemRow(&pBlockScanInfo->iiter, pBlockScanInfo->delSkyline, pReader);
+  }
+
+  // two levels of mem-table does contain the valid rows
+  if (pRow != NULL && piRow != NULL) {
+    return doMergeMultiLevelRows(pReader, pBlockScanInfo, pBlockData, pLastBlockReader);
+  }
+
+  // imem + file + last block
+  if (pBlockScanInfo->iiter.hasVal) {
+    return doMergeBufAndFileRows(pReader, pBlockScanInfo, piRow, &pBlockScanInfo->iiter, key, pLastBlockReader);
+  }
+
+  // mem + file + last block
+  if (pBlockScanInfo->iter.hasVal) {
+    return doMergeBufAndFileRows(pReader, pBlockScanInfo, pRow, &pBlockScanInfo->iter, key, pLastBlockReader);
+  }
+
+  // files data blocks + last block
+  return mergeFileBlockAndLastBlock(pReader, pLastBlockReader, key, pBlockScanInfo, pBlockData);
+}
+
+static int32_t loadNeighborIfOverlap(SFileDataBlockInfo* pBlockInfo, STableBlockScanInfo* pBlockScanInfo,
+                                     STsdbReader* pReader, bool* loadNeighbor) {
+  int32_t     code = TSDB_CODE_SUCCESS;
+  int32_t     step = ASCENDING_TRAVERSE(pReader->order) ? 1 : -1;
+  int32_t     nextIndex = -1;
+  SBlockIndex nxtBIndex = {0};
+
+  *loadNeighbor = false;
+  SDataBlk* pBlock = getCurrentBlock(&pReader->status.blockIter);
+
+  bool hasNeighbor = getNeighborBlockOfSameTable(pBlockInfo, pBlockScanInfo, &nextIndex, pReader->order, &nxtBIndex);
+  if (!hasNeighbor) {  // do nothing
+    return code;
+  }
+
+  if (overlapWithNeighborBlock(pBlock, &nxtBIndex, pReader->order)) {  // load next block
+    SReaderStatus*  pStatus = &pReader->status;
+    SDataBlockIter* pBlockIter = &pStatus->blockIter;
+
+    // 1. find the next neighbor block in the scan block list
+    SFileDataBlockInfo fb = {.uid = pBlockInfo->uid, .tbBlockIdx = nextIndex};
+    int32_t            neighborIndex = findFileBlockInfoIndex(pBlockIter, &fb);
+
+    // 2. remove it from the scan block list
+    setFileBlockActiveInBlockIter(pBlockIter, neighborIndex, step);
+
+    // 3. load the neighbor block, and set it to be the currently accessed file data block
+    code = doLoadFileBlockData(pReader, pBlockIter, &pStatus->fileBlockData, pBlockInfo->uid);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    // 4. check the data values
+    initBlockDumpInfo(pReader, pBlockIter);
+    *loadNeighbor = true;
+  }
+
+  return code;
+}
+
+static void updateComposedBlockInfo(STsdbReader* pReader, double el, STableBlockScanInfo* pBlockScanInfo) {
+  SSDataBlock* pResBlock = pReader->resBlockInfo.pResBlock;
+
+  pResBlock->info.id.uid = (pBlockScanInfo != NULL) ? pBlockScanInfo->uid : 0;
+  pResBlock->info.dataLoad = 1;
+  blockDataUpdateTsWindow(pResBlock, pReader->suppInfo.slotId[0]);
+
+  setComposedBlockFlag(pReader, true);
+
+  pReader->cost.composedBlocks += 1;
+  pReader->cost.buildComposedBlockTime += el;
+}
+
+static int32_t buildComposedDataBlock(STsdbReader* pReader) {
+  int32_t code = TSDB_CODE_SUCCESS;
+
+  SSDataBlock* pResBlock = pReader->resBlockInfo.pResBlock;
+
+  SFileDataBlockInfo* pBlockInfo = getCurrentBlockInfo(&pReader->status.blockIter);
+  SLastBlockReader*   pLastBlockReader = pReader->status.fileIter.pLastBlockReader;
+
+  bool    asc = ASCENDING_TRAVERSE(pReader->order);
+  int64_t st = taosGetTimestampUs();
+  int32_t step = asc ? 1 : -1;
+  double  el = 0;
+  SDataBlk* pBlock = getCurrentBlock(&pReader->status.blockIter);
+  SFileBlockDumpInfo* pDumpInfo = &pReader->status.fBlockDumpInfo;
+
+  STableBlockScanInfo* pBlockScanInfo = NULL;
+  if (pBlockInfo != NULL) {
+    if (pReader->pIgnoreTables && taosHashGet(*pReader->pIgnoreTables, &pBlockInfo->uid, sizeof(pBlockInfo->uid))) {
+      setBlockAllDumped(pDumpInfo, pBlock->maxKey.ts, pReader->order);
+      return code;
+    }
+
+    pBlockScanInfo = getTableBlockScanInfo(pReader->status.pTableMap, pBlockInfo->uid, pReader->idStr);
+    if (pBlockScanInfo == NULL) {
+      goto _end;
+    }
+
+    TSDBKEY   keyInBuf = getCurrentKeyInBuf(pBlockScanInfo, pReader);
+
+    // it is a clean block, load it directly
+    if (isCleanFileDataBlock(pReader, pBlockInfo, pBlock, pBlockScanInfo, keyInBuf, pLastBlockReader) &&
+        pBlock->nRow <= pReader->resBlockInfo.capacity) {
+      if (asc || (!hasDataInLastBlock(pLastBlockReader))) {
+        code = copyBlockDataToSDataBlock(pReader);
+        if (code) {
+          goto _end;
+        }
+
+        // record the last key value
+        pBlockScanInfo->lastKey = asc ? pBlock->maxKey.ts : pBlock->minKey.ts;
+        goto _end;
+      }
+    }
+  } else {  // file blocks not exist
+    pBlockScanInfo = *pReader->status.pTableIter;
+    if (pReader->pIgnoreTables && taosHashGet(*pReader->pIgnoreTables, &pBlockScanInfo->uid, sizeof(pBlockScanInfo->uid))) {
+      setBlockAllDumped(pDumpInfo, pBlock->maxKey.ts, pReader->order);
+      return code;
+    }
+  }
+
+  SBlockData* pBlockData = &pReader->status.fileBlockData;
+
+  while (1) {
+    bool hasBlockData = false;
+    {
+      while (pBlockData->nRow > 0 &&
+             pBlockData->uid == pBlockScanInfo->uid) {  // find the first qualified row in data block
+        if (isValidFileBlockRow(pBlockData, pDumpInfo, pBlockScanInfo, pReader)) {
+          hasBlockData = true;
+          break;
+        }
+
+        pDumpInfo->rowIndex += step;
+
+        pBlock = getCurrentBlock(&pReader->status.blockIter);
+        if (pDumpInfo->rowIndex >= pBlock->nRow || pDumpInfo->rowIndex < 0) {
+          pBlockInfo = getCurrentBlockInfo(&pReader->status.blockIter);  // NOTE: get the new block info
+
+          // continue check for the next file block if the last ts in the current block
+          // is overlapped with the next neighbor block
+          bool loadNeighbor = false;
+          code = loadNeighborIfOverlap(pBlockInfo, pBlockScanInfo, pReader, &loadNeighbor);
+          if ((!loadNeighbor) || (code != 0)) {
+            setBlockAllDumped(pDumpInfo, pBlock->maxKey.ts, pReader->order);
+            break;
+          }
+        }
+      }
+    }
+
+    // no data in last block and block, no need to proceed.
+    if (hasBlockData == false) {
+      break;
+    }
+
+    code = buildComposedDataBlockImpl(pReader, pBlockScanInfo, pBlockData, pLastBlockReader);
+    if (code) {
+      goto _end;
+    }
+
+    // currently loaded file data block is consumed
+    if ((pBlockData->nRow > 0) && (pDumpInfo->rowIndex >= pBlockData->nRow || pDumpInfo->rowIndex < 0)) {
+      pBlock = getCurrentBlock(&pReader->status.blockIter);
+      setBlockAllDumped(pDumpInfo, pBlock->maxKey.ts, pReader->order);
+      break;
+    }
+
+    if (pResBlock->info.rows >= pReader->resBlockInfo.capacity) {
+      break;
+    }
+  }
+
+  _end:
+  el = (taosGetTimestampUs() - st) / 1000.0;
+  updateComposedBlockInfo(pReader, el, pBlockScanInfo);
+
+  if (pResBlock->info.rows > 0) {
+    tsdbDebug("%p uid:%" PRIu64 ", composed data block created, brange:%" PRIu64 "-%" PRIu64 " rows:%" PRId64
+                  ", elapsed time:%.2f ms %s",
+              pReader, pResBlock->info.id.uid, pResBlock->info.window.skey, pResBlock->info.window.ekey,
+              pResBlock->info.rows, el, pReader->idStr);
+  }
+
+  return code;
+}
+
+void setComposedBlockFlag(STsdbReader* pReader, bool composed) { pReader->status.composedDataBlock = composed; }
+
+int32_t getInitialDelIndex(const SArray* pDelSkyline, int32_t order) {
+  if (pDelSkyline == NULL) {
+    return 0;
+  }
+
+  return ASCENDING_TRAVERSE(order) ? 0 : taosArrayGetSize(pDelSkyline) - 1;
+}
+
+int32_t initDelSkylineIterator(STableBlockScanInfo* pBlockScanInfo, STsdbReader* pReader, STbData* pMemTbData,
+                               STbData* piMemTbData) {
+  if (pBlockScanInfo->delSkyline != NULL) {
+    return TSDB_CODE_SUCCESS;
+  }
+
+  int32_t code = 0;
+  SArray* pDelData = taosArrayInit(4, sizeof(SDelData));
+
+  SDelFile* pDelFile = pReader->pReadSnap->fs.pDelFile;
+  if (pDelFile && taosArrayGetSize(pReader->pDelIdx) > 0) {
+    SDelIdx  idx = {.suid = pReader->suid, .uid = pBlockScanInfo->uid};
+    SDelIdx* pIdx = taosArraySearch(pReader->pDelIdx, &idx, tCmprDelIdx, TD_EQ);
+
+    if (pIdx != NULL) {
+      code = tsdbReadDelDatav1(pReader->pDelFReader, pIdx, pDelData, pReader->verRange.maxVer);
+    }
+    if (code != TSDB_CODE_SUCCESS) {
+      goto _err;
+    }
+  }
+
+  SDelData* p = NULL;
+  if (pMemTbData != NULL) {
+    p = pMemTbData->pHead;
+    while (p) {
+      if (p->version <= pReader->verRange.maxVer) {
+        taosArrayPush(pDelData, p);
+      }
+
+      p = p->pNext;
+    }
+  }
+
+  if (piMemTbData != NULL) {
+    p = piMemTbData->pHead;
+    while (p) {
+      if (p->version <= pReader->verRange.maxVer) {
+        taosArrayPush(pDelData, p);
+      }
+      p = p->pNext;
+    }
+  }
+
+  if (taosArrayGetSize(pDelData) > 0) {
+    pBlockScanInfo->delSkyline = taosArrayInit(4, sizeof(TSDBKEY));
+    code = tsdbBuildDeleteSkyline(pDelData, 0, (int32_t)(taosArrayGetSize(pDelData) - 1), pBlockScanInfo->delSkyline);
+  }
+
+  taosArrayDestroy(pDelData);
+  int32_t index = getInitialDelIndex(pBlockScanInfo->delSkyline, pReader->order);
+
+  pBlockScanInfo->iter.index = index;
+  pBlockScanInfo->iiter.index = index;
+  pBlockScanInfo->fileDelIndex = index;
+  pBlockScanInfo->lastBlockDelIndex = index;
+
+  return code;
+
+  _err:
+  taosArrayDestroy(pDelData);
+  return code;
+}
+
+TSDBKEY getCurrentKeyInBuf(STableBlockScanInfo* pScanInfo, STsdbReader* pReader) {
+  bool asc = ASCENDING_TRAVERSE(pReader->order);
+  //  TSKEY initialVal = asc? TSKEY_MIN:TSKEY_MAX;
+
+  TSDBKEY key = {.ts = TSKEY_INITIAL_VAL}, ikey = {.ts = TSKEY_INITIAL_VAL};
+
+  bool     hasKey = false, hasIKey = false;
+  TSDBROW* pRow = getValidMemRow(&pScanInfo->iter, pScanInfo->delSkyline, pReader);
+  if (pRow != NULL) {
+    hasKey = true;
+    key = TSDBROW_KEY(pRow);
+  }
+
+  TSDBROW* pIRow = getValidMemRow(&pScanInfo->iiter, pScanInfo->delSkyline, pReader);
+  if (pIRow != NULL) {
+    hasIKey = true;
+    ikey = TSDBROW_KEY(pIRow);
+  }
+
+  if (hasKey) {
+    if (hasIKey) {  // has data in mem & imem
+      if (asc) {
+        return key.ts <= ikey.ts ? key : ikey;
+      } else {
+        return key.ts <= ikey.ts ? ikey : key;
+      }
+    } else {  // no data in imem
+      return key;
+    }
+  } else {
+    // no data in mem & imem, return the initial value
+    // only imem has data, return ikey
+    return ikey;
+  }
+}
+
+static int32_t moveToNextFile(STsdbReader* pReader, SBlockNumber* pBlockNum, SArray* pTableList) {
+  SReaderStatus* pStatus = &pReader->status;
+  pBlockNum->numOfBlocks = 0;
+  pBlockNum->numOfLastFiles = 0;
+
+  size_t  numOfTables = tSimpleHashGetSize(pReader->status.pTableMap);
+  SArray* pIndexList = taosArrayInit(numOfTables, sizeof(SBlockIdx));
+
+  while (1) {
+    // only check here, since the iterate data in memory is very fast.
+    if (pReader->code != TSDB_CODE_SUCCESS) {
+      tsdbWarn("tsdb reader is stopped ASAP, code:%s, %s", strerror(pReader->code), pReader->idStr);
+      return pReader->code;
+    }
+
+    bool    hasNext = false;
+    int32_t code = filesetIteratorNext(&pStatus->fileIter, pReader, &hasNext);
+    if (code != TSDB_CODE_SUCCESS) {
+      taosArrayDestroy(pIndexList);
+      return code;
+    }
+
+    if (!hasNext) {  // no data files on disk
+      break;
+    }
+
+    taosArrayClear(pIndexList);
+    code = doLoadBlockIndex(pReader, pReader->pFileReader, pIndexList);
+    if (code != TSDB_CODE_SUCCESS) {
+      taosArrayDestroy(pIndexList);
+      return code;
+    }
+
+    if (taosArrayGetSize(pIndexList) > 0 || pReader->pFileReader->pSet->nSttF > 0) {
+      code = doLoadFileBlock(pReader, pIndexList, pBlockNum, pTableList);
+      if (code != TSDB_CODE_SUCCESS) {
+        taosArrayDestroy(pIndexList);
+        return code;
+      }
+
+      if (pBlockNum->numOfBlocks + pBlockNum->numOfLastFiles > 0) {
+        break;
+      }
+    }
+
+    // no blocks in current file, try next files
+  }
+
+  taosArrayDestroy(pIndexList);
+
+  if (pReader->pReadSnap != NULL) {
+    SDelFile* pDelFile = pReader->pReadSnap->fs.pDelFile;
+    if (pReader->pDelFReader == NULL && pDelFile != NULL) {
+      int32_t code = tsdbDelFReaderOpen(&pReader->pDelFReader, pDelFile, pReader->pTsdb);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+
+      pReader->pDelIdx = taosArrayInit(4, sizeof(SDelIdx));
+      if (pReader->pDelIdx == NULL) {
+        code = TSDB_CODE_OUT_OF_MEMORY;
+        return code;
+      }
+
+      code = tsdbReadDelIdx(pReader->pDelFReader, pReader->pDelIdx);
+      if (code != TSDB_CODE_SUCCESS) {
+        taosArrayDestroy(pReader->pDelIdx);
+        return code;
+      }
+    }
+  }
+
+  return TSDB_CODE_SUCCESS;
+}
+
+static void resetTableListIndex(SReaderStatus* pStatus) {
+  STableUidList* pList = &pStatus->uidList;
+
+  pList->currentIndex = 0;
+  uint64_t uid = pList->tableUidList[0];
+  pStatus->pTableIter = tSimpleHashGet(pStatus->pTableMap, &uid, sizeof(uid));
+}
+
+static bool moveToNextTable(STableUidList* pOrderedCheckInfo, SReaderStatus* pStatus) {
+  pOrderedCheckInfo->currentIndex += 1;
+  if (pOrderedCheckInfo->currentIndex >= tSimpleHashGetSize(pStatus->pTableMap)) {
+    pStatus->pTableIter = NULL;
+    return false;
+  }
+
+  uint64_t uid = pOrderedCheckInfo->tableUidList[pOrderedCheckInfo->currentIndex];
+  pStatus->pTableIter = tSimpleHashGet(pStatus->pTableMap, &uid, sizeof(uid));
+  return (pStatus->pTableIter != NULL);
+}
+
+static int32_t doLoadLastBlockSequentially(STsdbReader* pReader) {
+  SReaderStatus*    pStatus = &pReader->status;
+  SLastBlockReader* pLastBlockReader = pStatus->fileIter.pLastBlockReader;
+  STableUidList*    pUidList = &pStatus->uidList;
+  int32_t           code = TSDB_CODE_SUCCESS;
+
+  if (tSimpleHashGetSize(pStatus->pTableMap) == 0) {
+    return TSDB_CODE_SUCCESS;
+  }
+
+  SSDataBlock* pResBlock = pReader->resBlockInfo.pResBlock;
+
+  while (1) {
+    if (pReader->code != TSDB_CODE_SUCCESS) {
+      tsdbWarn("tsdb reader is stopped ASAP, code:%s, %s", strerror(pReader->code), pReader->idStr);
+      return pReader->code;
+    }
+
+    // load the last data block of current table
+    STableBlockScanInfo* pScanInfo = *(STableBlockScanInfo**)pStatus->pTableIter;
+    if (pReader->pIgnoreTables && taosHashGet(*pReader->pIgnoreTables, &pScanInfo->uid, sizeof(pScanInfo->uid))) {
+      // reset the index in last block when handing a new file
+      doCleanupTableScanInfo(pScanInfo);
+      pStatus->mapDataCleaned = true;
+
+      bool hasNexTable = moveToNextTable(pUidList, pStatus);
+      if (!hasNexTable) {
+        return TSDB_CODE_SUCCESS;
+      }
+
+      continue;
+    }
+
+    // reset the index in last block when handing a new file
+    doCleanupTableScanInfo(pScanInfo);
+    pStatus->mapDataCleaned = true;
+
+    bool hasDataInLastFile = initLastBlockReader(pLastBlockReader, pScanInfo, pReader);
+    if (!hasDataInLastFile) {
+      bool hasNexTable = moveToNextTable(pUidList, pStatus);
+      if (!hasNexTable) {
+        return TSDB_CODE_SUCCESS;
+      }
+
+      continue;
+    }
+
+    int64_t st = taosGetTimestampUs();
+    while (1) {
+      bool hasBlockLData = hasDataInLastBlock(pLastBlockReader);
+
+      // no data in last block and block, no need to proceed.
+      if (hasBlockLData == false) {
+        break;
+      }
+
+      code = buildComposedDataBlockImpl(pReader, pScanInfo, &pReader->status.fileBlockData, pLastBlockReader);
+      if (code) {
+        return code;
+      }
+
+      if (pResBlock->info.rows >= pReader->resBlockInfo.capacity) {
+        break;
+      }
+    }
+
+    double el = (taosGetTimestampUs() - st) / 1000.0;
+    updateComposedBlockInfo(pReader, el, pScanInfo);
+
+    if (pResBlock->info.rows > 0) {
+      tsdbDebug("%p uid:%" PRIu64 ", composed data block created, brange:%" PRIu64 "-%" PRIu64 " rows:%" PRId64
+                    ", elapsed time:%.2f ms %s",
+                pReader, pResBlock->info.id.uid, pResBlock->info.window.skey, pResBlock->info.window.ekey,
+                pResBlock->info.rows, el, pReader->idStr);
+      return TSDB_CODE_SUCCESS;
+    }
+
+    // current table is exhausted, let's try next table
+    bool hasNexTable = moveToNextTable(pUidList, pStatus);
+    if (!hasNexTable) {
+      return TSDB_CODE_SUCCESS;
+    }
+  }
+}
+
+static int32_t doBuildDataBlock(STsdbReader* pReader) {
+  int32_t   code = TSDB_CODE_SUCCESS;
+
+  SReaderStatus*       pStatus = &pReader->status;
+  SDataBlockIter*      pBlockIter = &pStatus->blockIter;
+  STableBlockScanInfo* pScanInfo = NULL;
+  SFileDataBlockInfo*  pBlockInfo = getCurrentBlockInfo(pBlockIter);
+  SLastBlockReader*    pLastBlockReader = pReader->status.fileIter.pLastBlockReader;
+  SDataBlk*            pBlock = getCurrentBlock(pBlockIter);
+
+  if (pReader->pIgnoreTables && taosHashGet(*pReader->pIgnoreTables, &pBlockInfo->uid, sizeof(pBlockInfo->uid))) {
+    setBlockAllDumped(&pStatus->fBlockDumpInfo, pBlock->maxKey.ts, pReader->order);
+    return code;
+  }
+
+  if (pReader->code != TSDB_CODE_SUCCESS) {
+    return pReader->code;
+  }
+
+  pScanInfo = getTableBlockScanInfo(pReader->status.pTableMap, pBlockInfo->uid, pReader->idStr);
+  if (pScanInfo == NULL) {
+    return terrno;
+  }
+
+
+  initLastBlockReader(pLastBlockReader, pScanInfo, pReader);
+  TSDBKEY keyInBuf = getCurrentKeyInBuf(pScanInfo, pReader);
+
+  if (fileBlockShouldLoad(pReader, pBlockInfo, pBlock, pScanInfo, keyInBuf, pLastBlockReader)) {
+    code = doLoadFileBlockData(pReader, pBlockIter, &pStatus->fileBlockData, pScanInfo->uid);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    // build composed data block
+    code = buildComposedDataBlock(pReader);
+  } else if (bufferDataInFileBlockGap(pReader->order, keyInBuf, pBlock)) {
+    // data in memory that are earlier than current file block
+    // 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 {
+    if (hasDataInLastBlock(pLastBlockReader) && !ASCENDING_TRAVERSE(pReader->order)) {
+      // only return the rows in last block
+      int64_t tsLast = getCurrentKeyInLastBlock(pLastBlockReader);
+      ASSERT(tsLast >= pBlock->maxKey.ts);
+
+      SBlockData* pBData = &pReader->status.fileBlockData;
+      tBlockDataReset(pBData);
+
+      SSDataBlock* pResBlock = pReader->resBlockInfo.pResBlock;
+      tsdbDebug("load data in last block firstly, due to desc scan data, %s", pReader->idStr);
+
+      int64_t st = taosGetTimestampUs();
+
+      while (1) {
+        bool hasBlockLData = hasDataInLastBlock(pLastBlockReader);
+
+        // no data in last block and block, no need to proceed.
+        if (hasBlockLData == false) {
+          break;
+        }
+
+        code = buildComposedDataBlockImpl(pReader, pScanInfo, &pReader->status.fileBlockData, pLastBlockReader);
+        if (code) {
+          return code;
+        }
+
+        if (pResBlock->info.rows >= pReader->resBlockInfo.capacity) {
+          break;
+        }
+      }
+
+      double el = (taosGetTimestampUs() - st) / 1000.0;
+      updateComposedBlockInfo(pReader, el, pScanInfo);
+
+      if (pResBlock->info.rows > 0) {
+        tsdbDebug("%p uid:%" PRIu64 ", composed data block created, brange:%" PRIu64 "-%" PRIu64 " rows:%" PRId64
+                      ", elapsed time:%.2f ms %s",
+                  pReader, pResBlock->info.id.uid, pResBlock->info.window.skey, pResBlock->info.window.ekey,
+                  pResBlock->info.rows, el, pReader->idStr);
+      }
+    } else {  // whole block is required, return it directly
+      SDataBlockInfo* pInfo = &pReader->resBlockInfo.pResBlock->info;
+      pInfo->rows = pBlock->nRow;
+      pInfo->id.uid = pScanInfo->uid;
+      pInfo->dataLoad = 0;
+      pInfo->window = (STimeWindow){.skey = pBlock->minKey.ts, .ekey = pBlock->maxKey.ts};
+      setComposedBlockFlag(pReader, false);
+      setBlockAllDumped(&pStatus->fBlockDumpInfo, pBlock->maxKey.ts, pReader->order);
+
+      // update the last key for the corresponding table
+      pScanInfo->lastKey = ASCENDING_TRAVERSE(pReader->order) ? pInfo->window.ekey : pInfo->window.skey;
+      tsdbDebug("%p uid:%" PRIu64
+                    " clean file block retrieved from file, global index:%d, "
+                    "table index:%d, rows:%d, brange:%" PRId64 "-%" PRId64 ", %s",
+                pReader, pScanInfo->uid, pBlockIter->index, pBlockInfo->tbBlockIdx, pBlock->nRow, pBlock->minKey.ts,
+                pBlock->maxKey.ts, pReader->idStr);
+    }
+  }
+
+  return (pReader->code != TSDB_CODE_SUCCESS)? pReader->code:code;
+}
+
+static int32_t doSumFileBlockRows(STsdbReader* pReader, SDataFReader* pFileReader) {
+  int64_t    st = taosGetTimestampUs();
+  LRUHandle* handle = NULL;
+  int32_t    code = tsdbCacheGetBlockIdx(pFileReader->pTsdb->biCache, pFileReader, &handle);
+  if (code != TSDB_CODE_SUCCESS || handle == NULL) {
+    goto _end;
+  }
+
+  int32_t numOfTables = tSimpleHashGetSize(pReader->status.pTableMap);
+
+  SArray* aBlockIdx = (SArray*)taosLRUCacheValue(pFileReader->pTsdb->biCache, handle);
+  size_t  num = taosArrayGetSize(aBlockIdx);
+  if (num == 0) {
+    tsdbBICacheRelease(pFileReader->pTsdb->biCache, handle);
+    return TSDB_CODE_SUCCESS;
+  }
+
+  SBlockIdx* pBlockIdx = NULL;
+  for (int32_t i = 0; i < num; ++i) {
+    pBlockIdx = (SBlockIdx*)taosArrayGet(aBlockIdx, i);
+    if (pBlockIdx->suid != pReader->suid) {
+      continue;
+    }
+
+    STableBlockScanInfo** p = tSimpleHashGet(pReader->status.pTableMap, &pBlockIdx->uid, sizeof(pBlockIdx->uid));
+    if (p == NULL) {
+      continue;
+    }
+
+    STableBlockScanInfo* pScanInfo = *p;
+    tMapDataReset(&pScanInfo->mapData);
+    tsdbReadDataBlk(pReader->pFileReader, pBlockIdx, &pScanInfo->mapData);
+
+    SDataBlk block = {0};
+    for (int32_t j = 0; j < pScanInfo->mapData.nItem; ++j) {
+      tGetDataBlk(pScanInfo->mapData.pData + pScanInfo->mapData.aOffset[j], &block);
+      pReader->rowsNum += block.nRow;
+    }
+  }
+
+  _end:
+  tsdbBICacheRelease(pFileReader->pTsdb->biCache, handle);
+  return code;
+}
+
+static int32_t doSumSttBlockRows(STsdbReader* pReader) {
+  int32_t            code = TSDB_CODE_SUCCESS;
+  SLastBlockReader*  pLastBlockReader = pReader->status.fileIter.pLastBlockReader;
+  SSttBlockLoadInfo* pBlockLoadInfo = NULL;
+
+  for (int32_t i = 0; i < pReader->pFileReader->pSet->nSttF; ++i) {  // open all last file
+    pBlockLoadInfo = &pLastBlockReader->pInfo[i];
+
+    code = tsdbReadSttBlk(pReader->pFileReader, i, pBlockLoadInfo->aSttBlk);
+    if (code) {
+      return code;
+    }
+
+    size_t size = taosArrayGetSize(pBlockLoadInfo->aSttBlk);
+    if (size >= 1) {
+      SSttBlk* pStart = taosArrayGet(pBlockLoadInfo->aSttBlk, 0);
+      SSttBlk* pEnd = taosArrayGet(pBlockLoadInfo->aSttBlk, size - 1);
+
+      // all identical
+      if (pStart->suid == pEnd->suid) {
+        if (pStart->suid != pReader->suid) {
+          // no qualified stt block existed
+          taosArrayClear(pBlockLoadInfo->aSttBlk);
+          continue;
+        }
+        for (int32_t j = 0; j < size; ++j) {
+          SSttBlk* p = taosArrayGet(pBlockLoadInfo->aSttBlk, j);
+          pReader->rowsNum += p->nRow;
+        }
+      } else {
+        for (int32_t j = 0; j < size; ++j) {
+          SSttBlk* p = taosArrayGet(pBlockLoadInfo->aSttBlk, j);
+          uint64_t s = p->suid;
+          if (s < pReader->suid) {
+            continue;
+          }
+
+          if (s == pReader->suid) {
+            pReader->rowsNum += p->nRow;
+          } else if (s > pReader->suid) {
+            break;
+          }
+        }
+      }
+    }
+  }
+
+  return code;
+}
+
+static int32_t readRowsCountFromFiles(STsdbReader* pReader) {
+  int32_t code = TSDB_CODE_SUCCESS;
+
+  while (1) {
+    bool hasNext = false;
+    code = filesetIteratorNext(&pReader->status.fileIter, pReader, &hasNext);
+    if (code) {
+      return code;
+    }
+
+    if (!hasNext) {  // no data files on disk
+      break;
+    }
+
+    code = doSumFileBlockRows(pReader, pReader->pFileReader);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    code = doSumSttBlockRows(pReader);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+  }
+
+  pReader->status.loadFromFile = false;
+
+  return code;
+}
+
+static int32_t readRowsCountFromMem(STsdbReader* pReader) {
+  int32_t code = TSDB_CODE_SUCCESS;
+  int64_t memNum = 0, imemNum = 0;
+  if (pReader->pReadSnap->pMem != NULL) {
+    tsdbMemTableCountRows(pReader->pReadSnap->pMem, pReader->status.pTableMap, &memNum);
+  }
+
+  if (pReader->pReadSnap->pIMem != NULL) {
+    tsdbMemTableCountRows(pReader->pReadSnap->pIMem, pReader->status.pTableMap, &imemNum);
+  }
+
+  pReader->rowsNum += memNum + imemNum;
+
+  return code;
+}
+
+static int32_t buildBlockFromBufferSequentially(STsdbReader* pReader) {
+  SReaderStatus* pStatus = &pReader->status;
+  STableUidList* pUidList = &pStatus->uidList;
+
+  while (1) {
+    if (pReader->code != TSDB_CODE_SUCCESS) {
+      tsdbWarn("tsdb reader is stopped ASAP, code:%s, %s", strerror(pReader->code), pReader->idStr);
+      return pReader->code;
+    }
+
+    STableBlockScanInfo** pBlockScanInfo = pStatus->pTableIter;
+    if (pReader->pIgnoreTables && taosHashGet(*pReader->pIgnoreTables, &(*pBlockScanInfo)->uid, sizeof((*pBlockScanInfo)->uid))) {
+      bool hasNexTable = moveToNextTable(pUidList, pStatus);
+      if (!hasNexTable) {
+        return TSDB_CODE_SUCCESS;
+      }
+      pBlockScanInfo = pStatus->pTableIter;
+    }
+
+    initMemDataIterator(*pBlockScanInfo, pReader);
+
+    int64_t endKey = (ASCENDING_TRAVERSE(pReader->order)) ? INT64_MAX : INT64_MIN;
+    int32_t code = buildDataBlockFromBuf(pReader, *pBlockScanInfo, endKey);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    if (pReader->resBlockInfo.pResBlock->info.rows > 0) {
+      return TSDB_CODE_SUCCESS;
+    }
+
+    // current table is exhausted, let's try next table
+    bool hasNexTable = moveToNextTable(pUidList, pStatus);
+    if (!hasNexTable) {
+      return TSDB_CODE_SUCCESS;
+    }
+  }
+}
+
+// set the correct start position in case of the first/last file block, according to the query time window
+static void initBlockDumpInfo(STsdbReader* pReader, SDataBlockIter* pBlockIter) {
+  int64_t             lastKey = ASCENDING_TRAVERSE(pReader->order) ? INT64_MIN : INT64_MAX;
+  SDataBlk*           pBlock = getCurrentBlock(pBlockIter);
+  SFileDataBlockInfo* pBlockInfo = getCurrentBlockInfo(pBlockIter);
+  if (pBlockInfo) {
+    STableBlockScanInfo* pScanInfo = tSimpleHashGet(pBlockIter->pTableMap, &pBlockInfo->uid, sizeof(pBlockInfo->uid));
+    if (pScanInfo) {
+      lastKey = pScanInfo->lastKey;
+    }
+  }
+  SReaderStatus* pStatus = &pReader->status;
+
+  SFileBlockDumpInfo* pDumpInfo = &pStatus->fBlockDumpInfo;
+
+  pDumpInfo->totalRows = pBlock->nRow;
+  pDumpInfo->allDumped = false;
+  pDumpInfo->rowIndex = ASCENDING_TRAVERSE(pReader->order) ? 0 : pBlock->nRow - 1;
+  pDumpInfo->lastKey = lastKey;
+}
+
+static int32_t initForFirstBlockInFile(STsdbReader* pReader, SDataBlockIter* pBlockIter) {
+  SBlockNumber num = {0};
+  SArray* pTableList = taosArrayInit(40, POINTER_BYTES);
+
+  int32_t code = moveToNextFile(pReader, &num, pTableList);
+  if (code != TSDB_CODE_SUCCESS) {
+    taosArrayDestroy(pTableList);
+    return code;
+  }
+
+  // all data files are consumed, try data in buffer
+  if (num.numOfBlocks + num.numOfLastFiles == 0) {
+    pReader->status.loadFromFile = false;
+    taosArrayDestroy(pTableList);
+    return code;
+  }
+
+  // initialize the block iterator for a new fileset
+  if (num.numOfBlocks > 0) {
+    code = initBlockIterator(pReader, pBlockIter, num.numOfBlocks, pTableList);
+  } else {  // no block data, only last block exists
+    tBlockDataReset(&pReader->status.fileBlockData);
+    resetDataBlockIterator(pBlockIter, pReader->order);
+    resetTableListIndex(&pReader->status);
+  }
+
+  // set the correct start position according to the query time window
+  initBlockDumpInfo(pReader, pBlockIter);
+  taosArrayDestroy(pTableList);
+  return code;
+}
+
+static bool fileBlockPartiallyRead(SFileBlockDumpInfo* pDumpInfo, bool asc) {
+  return (!pDumpInfo->allDumped) &&
+         ((pDumpInfo->rowIndex > 0 && asc) || (pDumpInfo->rowIndex < (pDumpInfo->totalRows - 1) && (!asc)));
+}
+
+typedef enum {
+  TSDB_READ_RETURN = 0x1,
+  TSDB_READ_CONTINUE = 0x2,
+} ERetrieveType;
+
+static ERetrieveType doReadDataFromLastFiles(STsdbReader* pReader) {
+  int32_t         code = TSDB_CODE_SUCCESS;
+  SSDataBlock*    pResBlock = pReader->resBlockInfo.pResBlock;
+  SDataBlockIter* pBlockIter = &pReader->status.blockIter;
+
+  while(1) {
+    terrno = 0;
+
+    code = doLoadLastBlockSequentially(pReader);
+    if (code != TSDB_CODE_SUCCESS) {
+      terrno = code;
+      return TSDB_READ_RETURN;
+    }
+
+    if (pResBlock->info.rows > 0) {
+      return TSDB_READ_RETURN;
+    }
+
+    // all data blocks are checked in this last block file, now let's try the next file
+    ASSERT(pReader->status.pTableIter == NULL);
+    code = initForFirstBlockInFile(pReader, pBlockIter);
+
+    // error happens or all the data files are completely checked
+    if ((code != TSDB_CODE_SUCCESS) || (pReader->status.loadFromFile == false)) {
+      terrno = code;
+      return TSDB_READ_RETURN;
+    }
+
+    if (pBlockIter->numOfBlocks > 0) { // there are data blocks existed.
+      return TSDB_READ_CONTINUE;
+    } else {  // all blocks in data file are checked, let's check the data in last files
+      resetTableListIndex(&pReader->status);
+    }
+  }
+}
+
+static int32_t buildBlockFromFiles(STsdbReader* pReader) {
+  int32_t code = TSDB_CODE_SUCCESS;
+  bool    asc = ASCENDING_TRAVERSE(pReader->order);
+
+  SDataBlockIter* pBlockIter = &pReader->status.blockIter;
+  SSDataBlock* pResBlock = pReader->resBlockInfo.pResBlock;
+
+  if (pBlockIter->numOfBlocks == 0) {
+    // let's try to extract data from stt files.
+    ERetrieveType type = doReadDataFromLastFiles(pReader);
+    if (type == TSDB_READ_RETURN) {
+      return terrno;
+    }
+
+    code = doBuildDataBlock(pReader);
+    if (code != TSDB_CODE_SUCCESS || pResBlock->info.rows > 0) {
+      return code;
+    }
+  }
+
+  while (1) {
+    SFileBlockDumpInfo* pDumpInfo = &pReader->status.fBlockDumpInfo;
+
+    if (fileBlockPartiallyRead(pDumpInfo, asc)) {  // file data block is partially loaded
+      code = buildComposedDataBlock(pReader);
+    } else {
+      // current block are exhausted, try the next file block
+      if (pDumpInfo->allDumped) {
+        // try next data block in current file
+        bool hasNext = blockIteratorNext(&pReader->status.blockIter, pReader->idStr);
+        if (hasNext) {  // check for the next block in the block accessed order list
+          initBlockDumpInfo(pReader, pBlockIter);
+        } else {
+          // all data blocks in files are checked, let's check the data in last files.
+          ASSERT(pReader->status.pCurrentFileset->nSttF > 0);
+
+          // data blocks in current file are exhausted, let's try the next file now
+          SBlockData* pBlockData = &pReader->status.fileBlockData;
+          if (pBlockData->uid != 0) {
+            tBlockDataClear(pBlockData);
+          }
+
+          tBlockDataReset(pBlockData);
+          resetDataBlockIterator(pBlockIter, pReader->order);
+          resetTableListIndex(&pReader->status);
+
+          ERetrieveType type = doReadDataFromLastFiles(pReader);
+          if (type == TSDB_READ_RETURN) {
+            return terrno;
+          }
+        }
+      }
+
+      code = doBuildDataBlock(pReader);
+    }
+
+    if (code != TSDB_CODE_SUCCESS || pResBlock->info.rows > 0) {
+      return code;
+    }
+  }
+}
+
+static STsdb* getTsdbByRetentions(SVnode* pVnode, TSKEY winSKey, SRetention* retentions, const char* idStr,
+                                  int8_t* pLevel) {
+  if (VND_IS_RSMA(pVnode)) {
+    int8_t  level = 0;
+    int8_t  precision = pVnode->config.tsdbCfg.precision;
+    int64_t now = taosGetTimestamp(precision);
+    int64_t offset = tsQueryRsmaTolerance * ((precision == TSDB_TIME_PRECISION_MILLI)   ? 1L
+                                                                                        : (precision == TSDB_TIME_PRECISION_MICRO) ? 1000L
+                                                                                                                                   : 1000000L);
+
+    for (int8_t i = 0; i < TSDB_RETENTION_MAX; ++i) {
+      SRetention* pRetention = retentions + level;
+      if (pRetention->keep <= 0) {
+        if (level > 0) {
+          --level;
+        }
+        break;
+      }
+      if ((now - pRetention->keep) <= (winSKey + offset)) {
+        break;
+      }
+      ++level;
+    }
+
+    const char* str = (idStr != NULL) ? idStr : "";
+
+    if (level == TSDB_RETENTION_L0) {
+      *pLevel = TSDB_RETENTION_L0;
+      tsdbDebug("vgId:%d, rsma level %d is selected to query %s", TD_VID(pVnode), TSDB_RETENTION_L0, str);
+      return VND_RSMA0(pVnode);
+    } else if (level == TSDB_RETENTION_L1) {
+      *pLevel = TSDB_RETENTION_L1;
+      tsdbDebug("vgId:%d, rsma level %d is selected to query %s", TD_VID(pVnode), TSDB_RETENTION_L1, str);
+      return VND_RSMA1(pVnode);
+    } else {
+      *pLevel = TSDB_RETENTION_L2;
+      tsdbDebug("vgId:%d, rsma level %d is selected to query %s", TD_VID(pVnode), TSDB_RETENTION_L2, str);
+      return VND_RSMA2(pVnode);
+    }
+  }
+
+  return VND_TSDB(pVnode);
+}
+
+SVersionRange getQueryVerRange(SVnode* pVnode, SQueryTableDataCond* pCond, int8_t level) {
+  int64_t startVer = (pCond->startVersion == -1) ? 0 : pCond->startVersion;
+
+  int64_t endVer = 0;
+  if (pCond->endVersion == -1) {
+    // user not specified end version, set current maximum version of vnode as the endVersion
+    endVer = pVnode->state.applied;
+  } else {
+    endVer = (pCond->endVersion > pVnode->state.applied) ? pVnode->state.applied : pCond->endVersion;
+  }
+
+  return (SVersionRange){.minVer = startVer, .maxVer = endVer};
+}
+
+bool hasBeenDropped(const SArray* pDelList, int32_t* index, int64_t key, int64_t ver, int32_t order, SVersionRange* pVerRange) {
+  if (pDelList == NULL) {
+    return false;
+  }
+
+  size_t  num = taosArrayGetSize(pDelList);
+  bool    asc = ASCENDING_TRAVERSE(order);
+  int32_t step = asc ? 1 : -1;
+
+  if (asc) {
+    if (*index >= num - 1) {
+      TSDBKEY* last = taosArrayGetLast(pDelList);
+      ASSERT(key >= last->ts);
+
+      if (key > last->ts) {
+        return false;
+      } else if (key == last->ts) {
+        TSDBKEY* prev = taosArrayGet(pDelList, num - 2);
+        return (prev->version >= ver && prev->version <= pVerRange->maxVer &&
+                prev->version >= pVerRange->minVer);
+      }
+    } else {
+      TSDBKEY* pCurrent = taosArrayGet(pDelList, *index);
+      TSDBKEY* pNext = taosArrayGet(pDelList, (*index) + 1);
+
+      if (key < pCurrent->ts) {
+        return false;
+      }
+
+      if (pCurrent->ts <= key && pNext->ts >= key && pCurrent->version >= ver &&
+          pVerRange->maxVer >= pCurrent->version) {
+        return true;
+      }
+
+      while (pNext->ts <= key && (*index) < num - 1) {
+        (*index) += 1;
+
+        if ((*index) < num - 1) {
+          pCurrent = taosArrayGet(pDelList, *index);
+          pNext = taosArrayGet(pDelList, (*index) + 1);
+
+          // it is not a consecutive deletion range, ignore it
+          if (pCurrent->version == 0 && pNext->version > 0) {
+            continue;
+          }
+
+          if (pCurrent->ts <= key && pNext->ts >= key && pCurrent->version >= ver &&
+              pVerRange->maxVer >= pCurrent->version) {
+            return true;
+          }
+        }
+      }
+
+      return false;
+    }
+  } else {
+    if (*index <= 0) {
+      TSDBKEY* pFirst = taosArrayGet(pDelList, 0);
+
+      if (key < pFirst->ts) {
+        return false;
+      } else if (key == pFirst->ts) {
+        return pFirst->version >= ver;
+      } else {
+        ASSERT(0);
+      }
+    } else {
+      TSDBKEY* pCurrent = taosArrayGet(pDelList, *index);
+      TSDBKEY* pPrev = taosArrayGet(pDelList, (*index) - 1);
+
+      if (key > pCurrent->ts) {
+        return false;
+      }
+
+      if (pPrev->ts <= key && pCurrent->ts >= key && pPrev->version >= ver) {
+        return true;
+      }
+
+      while (pPrev->ts >= key && (*index) > 1) {
+        (*index) += step;
+
+        if ((*index) >= 1) {
+          pCurrent = taosArrayGet(pDelList, *index);
+          pPrev = taosArrayGet(pDelList, (*index) - 1);
+
+          // it is not a consecutive deletion range, ignore it
+          if (pCurrent->version > 0 && pPrev->version == 0) {
+            continue;
+          }
+
+          if (pPrev->ts <= key && pCurrent->ts >= key && pPrev->version >= ver) {
+            return true;
+          }
+        }
+      }
+
+      return false;
+    }
+  }
+
+  return false;
+}
+
+TSDBROW* getValidMemRow(SIterInfo* pIter, const SArray* pDelList, STsdbReader* pReader) {
+  if (!pIter->hasVal) {
+    return NULL;
+  }
+
+  TSDBROW* pRow = tsdbTbDataIterGet(pIter->iter);
+  TSDBKEY  key = TSDBROW_KEY(pRow);
+
+  if (outOfTimeWindow(key.ts, &pReader->window)) {
+    pIter->hasVal = false;
+    return NULL;
+  }
+
+  // it is a valid data version
+  if ((key.version <= pReader->verRange.maxVer && key.version >= pReader->verRange.minVer) &&
+      (!hasBeenDropped(pDelList, &pIter->index, key.ts, key.version, pReader->order, &pReader->verRange))) {
+    return pRow;
+  }
+
+  while (1) {
+    pIter->hasVal = tsdbTbDataIterNext(pIter->iter);
+    if (!pIter->hasVal) {
+      return NULL;
+    }
+
+    pRow = tsdbTbDataIterGet(pIter->iter);
+
+    key = TSDBROW_KEY(pRow);
+    if (outOfTimeWindow(key.ts, &pReader->window)) {
+      pIter->hasVal = false;
+      return NULL;
+    }
+
+    if (key.version <= pReader->verRange.maxVer && key.version >= pReader->verRange.minVer &&
+        (!hasBeenDropped(pDelList, &pIter->index, key.ts, key.version, pReader->order, &pReader->verRange))) {
+      return pRow;
+    }
+  }
+}
+
+int32_t doMergeRowsInBuf(SIterInfo* pIter, uint64_t uid, int64_t ts, SArray* pDelList, STsdbReader* pReader) {
+  SRowMerger* pMerger = &pReader->status.merger;
+
+  while (1) {
+    pIter->hasVal = tsdbTbDataIterNext(pIter->iter);
+    if (!pIter->hasVal) {
+      break;
+    }
+
+    // data exists but not valid
+    TSDBROW* pRow = getValidMemRow(pIter, pDelList, pReader);
+    if (pRow == NULL) {
+      break;
+    }
+
+    // ts is not identical, quit
+    TSDBKEY k = TSDBROW_KEY(pRow);
+    if (k.ts != ts) {
+      break;
+    }
+
+    if (pRow->type == TSDBROW_ROW_FMT) {
+      STSchema* pTSchema = doGetSchemaForTSRow(TSDBROW_SVERSION(pRow), pReader, uid);
+      if (pTSchema == NULL) {
+        return terrno;
+      }
+
+      tsdbRowMergerAdd(pMerger, pRow, pTSchema);
+    } else {  // column format
+      tsdbRowMergerAdd(pMerger, pRow, NULL);
+    }
+  }
+
+  return TSDB_CODE_SUCCESS;
+}
+
+static int32_t doMergeRowsInFileBlockImpl(SBlockData* pBlockData, int32_t rowIndex, int64_t key, SRowMerger* pMerger,
+                                          SVersionRange* pVerRange, int32_t step) {
+  while (rowIndex < pBlockData->nRow && rowIndex >= 0 && pBlockData->aTSKEY[rowIndex] == key) {
+    if (pBlockData->aVersion[rowIndex] > pVerRange->maxVer || pBlockData->aVersion[rowIndex] < pVerRange->minVer) {
+      rowIndex += step;
+      continue;
+    }
+
+    TSDBROW fRow = tsdbRowFromBlockData(pBlockData, rowIndex);
+    tsdbRowMergerAdd(pMerger, &fRow, NULL);
+    rowIndex += step;
+  }
+
+  return rowIndex;
+}
+
+typedef enum {
+  CHECK_FILEBLOCK_CONT = 0x1,
+  CHECK_FILEBLOCK_QUIT = 0x2,
+} CHECK_FILEBLOCK_STATE;
+
+static int32_t checkForNeighborFileBlock(STsdbReader* pReader, STableBlockScanInfo* pScanInfo, SDataBlk* pBlock,
+                                         SFileDataBlockInfo* pFBlock, SRowMerger* pMerger, int64_t key,
+                                         CHECK_FILEBLOCK_STATE* state) {
+  SFileBlockDumpInfo* pDumpInfo = &pReader->status.fBlockDumpInfo;
+  SBlockData*         pBlockData = &pReader->status.fileBlockData;
+  bool                asc = ASCENDING_TRAVERSE(pReader->order);
+
+  *state = CHECK_FILEBLOCK_QUIT;
+  int32_t step = ASCENDING_TRAVERSE(pReader->order) ? 1 : -1;
+
+  bool    loadNeighbor = true;
+  int32_t code = loadNeighborIfOverlap(pFBlock, pScanInfo, pReader, &loadNeighbor);
+
+  if (loadNeighbor && (code == TSDB_CODE_SUCCESS)) {
+    pDumpInfo->rowIndex =
+        doMergeRowsInFileBlockImpl(pBlockData, pDumpInfo->rowIndex, key, pMerger, &pReader->verRange, step);
+    if ((pDumpInfo->rowIndex >= pDumpInfo->totalRows && asc) || (pDumpInfo->rowIndex < 0 && !asc)) {
+      *state = CHECK_FILEBLOCK_CONT;
+    }
+  }
+
+  return code;
+}
+
+int32_t doMergeRowsInFileBlocks(SBlockData* pBlockData, STableBlockScanInfo* pScanInfo, STsdbReader* pReader) {
+  SFileBlockDumpInfo* pDumpInfo = &pReader->status.fBlockDumpInfo;
+
+  SRowMerger* pMerger = &pReader->status.merger;
+  bool    asc = ASCENDING_TRAVERSE(pReader->order);
+  int64_t key = pBlockData->aTSKEY[pDumpInfo->rowIndex];
+  int32_t step = asc ? 1 : -1;
+
+  pDumpInfo->rowIndex += step;
+  if ((pDumpInfo->rowIndex <= pBlockData->nRow - 1 && asc) || (pDumpInfo->rowIndex >= 0 && !asc)) {
+    pDumpInfo->rowIndex =
+        doMergeRowsInFileBlockImpl(pBlockData, pDumpInfo->rowIndex, key, pMerger, &pReader->verRange, step);
+  }
+
+  // all rows are consumed, let's try next file block
+  if ((pDumpInfo->rowIndex >= pBlockData->nRow && asc) || (pDumpInfo->rowIndex < 0 && !asc)) {
+    while (1) {
+      CHECK_FILEBLOCK_STATE st;
+
+      SFileDataBlockInfo* pFileBlockInfo = getCurrentBlockInfo(&pReader->status.blockIter);
+      SDataBlk*           pCurrentBlock = getCurrentBlock(&pReader->status.blockIter);
+      if (pFileBlockInfo == NULL) {
+        st = CHECK_FILEBLOCK_QUIT;
+        break;
+      }
+
+      checkForNeighborFileBlock(pReader, pScanInfo, pCurrentBlock, pFileBlockInfo, pMerger, key, &st);
+      if (st == CHECK_FILEBLOCK_QUIT) {
+        break;
+      }
+    }
+  }
+
+  return TSDB_CODE_SUCCESS;
+}
+
+int32_t doMergeRowsInLastBlock(SLastBlockReader* pLastBlockReader, STableBlockScanInfo* pScanInfo, int64_t ts,
+                               SRowMerger* pMerger, SVersionRange* pVerRange, const char* idStr) {
+  while (nextRowFromLastBlocks(pLastBlockReader, pScanInfo, pVerRange)) {
+    int64_t next1 = getCurrentKeyInLastBlock(pLastBlockReader);
+    if (next1 == ts) {
+      TSDBROW* pRow1 = tMergeTreeGetRow(&pLastBlockReader->mergeTree);
+      tsdbRowMergerAdd(pMerger, pRow1, NULL);
+    } else {
+      tsdbTrace("uid:%" PRIu64 " last del index:%d, del range:%d, lastKeyInStt:%" PRId64 ", %s", pScanInfo->uid,
+                pScanInfo->lastBlockDelIndex, (int32_t)taosArrayGetSize(pScanInfo->delSkyline), pScanInfo->lastKeyInStt,
+                idStr);
+      break;
+    }
+  }
+
+  return TSDB_CODE_SUCCESS;
+}
+
+int32_t doMergeMemTableMultiRows(TSDBROW* pRow, uint64_t uid, SIterInfo* pIter, SArray* pDelList, TSDBROW* pResRow,
+                                 STsdbReader* pReader, bool* freeTSRow) {
+  TSDBROW* pNextRow = NULL;
+  TSDBROW  current = *pRow;
+
+  {  // if the timestamp of the next valid row has a different ts, return current row directly
+    pIter->hasVal = tsdbTbDataIterNext(pIter->iter);
+
+    if (!pIter->hasVal) {
+      *pResRow = *pRow;
+      *freeTSRow = false;
+      return TSDB_CODE_SUCCESS;
+    } else {  // has next point in mem/imem
+      pNextRow = getValidMemRow(pIter, pDelList, pReader);
+      if (pNextRow == NULL) {
+        *pResRow = current;
+        *freeTSRow = false;
+        return TSDB_CODE_SUCCESS;
+      }
+
+      if (TSDBROW_TS(&current) != TSDBROW_TS(pNextRow)) {
+        *pResRow = current;
+        *freeTSRow = false;
+        return TSDB_CODE_SUCCESS;
+      }
+    }
+  }
+
+  terrno = 0;
+  int32_t code = 0;
+
+  // start to merge duplicated rows
+  if (current.type == TSDBROW_ROW_FMT) {
+    // get the correct schema for data in memory
+    STSchema* pTSchema = doGetSchemaForTSRow(TSDBROW_SVERSION(&current), pReader, uid);
+    if (pTSchema == NULL) {
+      return terrno;
+    }
+
+    code = tsdbRowMergerAdd(&pReader->status.merger, &current, pTSchema);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    STSchema* pTSchema1 = doGetSchemaForTSRow(TSDBROW_SVERSION(pNextRow), pReader, uid);
+    if (pTSchema1 == NULL) {
+      return terrno;
+    }
+
+    tsdbRowMergerAdd(&pReader->status.merger,pNextRow, pTSchema1);
+  } else {  // let's merge rows in file block
+    code = tsdbRowMergerAdd(&pReader->status.merger, &current, pReader->pSchema);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    tsdbRowMergerAdd(&pReader->status.merger,pNextRow, NULL);
+  }
+
+  code = doMergeRowsInBuf(pIter, uid, TSDBROW_TS(&current), pDelList, pReader);
+  if (code != TSDB_CODE_SUCCESS) {
+    return code;
+  }
+
+  code = tsdbRowMergerGetRow(&pReader->status.merger, &pResRow->pTSRow);
+  if (code != TSDB_CODE_SUCCESS) {
+    return code;
+  }
+
+  pResRow->type = TSDBROW_ROW_FMT;
+  tsdbRowMergerClear(&pReader->status.merger);
+  *freeTSRow = true;
+
+  return TSDB_CODE_SUCCESS;
+}
+
+int32_t doMergeMemIMemRows(TSDBROW* pRow, TSDBROW* piRow, STableBlockScanInfo* pBlockScanInfo, STsdbReader* pReader,
+                           SRow** pTSRow) {
+  SRowMerger* pMerger = &pReader->status.merger;
+
+  TSDBKEY   k = TSDBROW_KEY(pRow);
+  TSDBKEY   ik = TSDBROW_KEY(piRow);
+  STSchema* pSchema = doGetSchemaForTSRow(TSDBROW_SVERSION(pRow), pReader, pBlockScanInfo->uid);
+  if (pSchema == NULL) {
+    return terrno;
+  }
+
+  STSchema* piSchema = doGetSchemaForTSRow(TSDBROW_SVERSION(piRow), pReader, pBlockScanInfo->uid);
+  if (piSchema == NULL) {
+    return terrno;
+  }
+
+  if (ASCENDING_TRAVERSE(pReader->order)) {  // ascending order imem --> mem
+    int32_t code = tsdbRowMergerAdd(&pReader->status.merger, piRow, piSchema);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    code = doMergeRowsInBuf(&pBlockScanInfo->iiter, pBlockScanInfo->uid, ik.ts, pBlockScanInfo->delSkyline, pReader);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    tsdbRowMergerAdd(&pReader->status.merger,pRow, pSchema);
+    code =
+        doMergeRowsInBuf(&pBlockScanInfo->iter, pBlockScanInfo->uid, k.ts, pBlockScanInfo->delSkyline, pReader);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+  } else {
+    int32_t code = tsdbRowMergerAdd(&pReader->status.merger, pRow, pSchema);
+    if (code != TSDB_CODE_SUCCESS || pMerger->pTSchema == NULL) {
+      return code;
+    }
+
+    code = doMergeRowsInBuf(&pBlockScanInfo->iter, pBlockScanInfo->uid, k.ts, pBlockScanInfo->delSkyline, pReader);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    tsdbRowMergerAdd(&pReader->status.merger, piRow, piSchema);
+    code = doMergeRowsInBuf(&pBlockScanInfo->iiter, pBlockScanInfo->uid, ik.ts, pBlockScanInfo->delSkyline, pReader);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+  }
+
+  int32_t code = tsdbRowMergerGetRow(pMerger, pTSRow);
+  tsdbRowMergerClear(pMerger);
+  return code;
+}
+
+int32_t tsdbGetNextRowInMem(STableBlockScanInfo* pBlockScanInfo, STsdbReader* pReader, TSDBROW* pResRow, int64_t endKey,
+                            bool* freeTSRow) {
+  TSDBROW* pRow = getValidMemRow(&pBlockScanInfo->iter, pBlockScanInfo->delSkyline, pReader);
+  TSDBROW* piRow = getValidMemRow(&pBlockScanInfo->iiter, pBlockScanInfo->delSkyline, pReader);
+  SArray*  pDelList = pBlockScanInfo->delSkyline;
+  uint64_t uid = pBlockScanInfo->uid;
+
+  // todo refactor
+  bool asc = ASCENDING_TRAVERSE(pReader->order);
+  if (pBlockScanInfo->iter.hasVal) {
+    TSDBKEY k = TSDBROW_KEY(pRow);
+    if ((k.ts >= endKey && asc) || (k.ts <= endKey && !asc)) {
+      pRow = NULL;
+    }
+  }
+
+  if (pBlockScanInfo->iiter.hasVal) {
+    TSDBKEY k = TSDBROW_KEY(piRow);
+    if ((k.ts >= endKey && asc) || (k.ts <= endKey && !asc)) {
+      piRow = NULL;
+    }
+  }
+
+  if (pBlockScanInfo->iter.hasVal && pBlockScanInfo->iiter.hasVal && pRow != NULL && piRow != NULL) {
+    TSDBKEY k = TSDBROW_KEY(pRow);
+    TSDBKEY ik = TSDBROW_KEY(piRow);
+
+    int32_t code = TSDB_CODE_SUCCESS;
+    if (ik.ts != k.ts) {
+      if (((ik.ts < k.ts) && asc) || ((ik.ts > k.ts) && (!asc))) {  // ik.ts < k.ts
+        code = doMergeMemTableMultiRows(piRow, uid, &pBlockScanInfo->iiter, pDelList, pResRow, pReader, freeTSRow);
+      } else if (((k.ts < ik.ts) && asc) || ((k.ts > ik.ts) && (!asc))) {
+        code = doMergeMemTableMultiRows(pRow, uid, &pBlockScanInfo->iter, pDelList, pResRow, pReader, freeTSRow);
+      }
+    } else {  // ik.ts == k.ts
+      *freeTSRow = true;
+      pResRow->type = TSDBROW_ROW_FMT;
+      code = doMergeMemIMemRows(pRow, piRow, pBlockScanInfo, pReader, &pResRow->pTSRow);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+    }
+
+    return code;
+  }
+
+  if (pBlockScanInfo->iter.hasVal && pRow != NULL) {
+    return doMergeMemTableMultiRows(pRow, pBlockScanInfo->uid, &pBlockScanInfo->iter, pDelList, pResRow, pReader,
+                                    freeTSRow);
+  }
+
+  if (pBlockScanInfo->iiter.hasVal && piRow != NULL) {
+    return doMergeMemTableMultiRows(piRow, uid, &pBlockScanInfo->iiter, pDelList, pResRow, pReader, freeTSRow);
+  }
+
+  return TSDB_CODE_SUCCESS;
+}
+
+int32_t doAppendRowFromTSRow(SSDataBlock* pBlock, STsdbReader* pReader, SRow* pTSRow, STableBlockScanInfo* pScanInfo) {
+  int32_t outputRowIndex = pBlock->info.rows;
+  int64_t uid = pScanInfo->uid;
+  int32_t code = TSDB_CODE_SUCCESS;
+
+  SBlockLoadSuppInfo* pSupInfo = &pReader->suppInfo;
+  STSchema*           pSchema = doGetSchemaForTSRow(pTSRow->sver, pReader, uid);
+  if (pSchema == NULL) {
+    return terrno;
+  }
+
+  SColVal colVal = {0};
+  int32_t i = 0, j = 0;
+
+  if (pSupInfo->colId[i] == PRIMARYKEY_TIMESTAMP_COL_ID) {
+    SColumnInfoData* pColData = taosArrayGet(pBlock->pDataBlock, pSupInfo->slotId[i]);
+    ((int64_t*)pColData->pData)[outputRowIndex] = pTSRow->ts;
+    i += 1;
+  }
+
+  while (i < pSupInfo->numOfCols && j < pSchema->numOfCols) {
+    col_id_t colId = pSupInfo->colId[i];
+
+    if (colId == pSchema->columns[j].colId) {
+      SColumnInfoData* pColInfoData = taosArrayGet(pBlock->pDataBlock, pSupInfo->slotId[i]);
+
+      tRowGet(pTSRow, pSchema, j, &colVal);
+      code = doCopyColVal(pColInfoData, outputRowIndex, i, &colVal, pSupInfo);
+      if (code) {
+        return code;
+      }
+      i += 1;
+      j += 1;
+    } else if (colId < pSchema->columns[j].colId) {
+      SColumnInfoData* pColInfoData = taosArrayGet(pBlock->pDataBlock, pSupInfo->slotId[i]);
+
+      colDataSetNULL(pColInfoData, outputRowIndex);
+      i += 1;
+    } else if (colId > pSchema->columns[j].colId) {
+      j += 1;
+    }
+  }
+
+  // set null value since current column does not exist in the "pSchema"
+  while (i < pSupInfo->numOfCols) {
+    SColumnInfoData* pColInfoData = taosArrayGet(pBlock->pDataBlock, pSupInfo->slotId[i]);
+    colDataSetNULL(pColInfoData, outputRowIndex);
+    i += 1;
+  }
+
+  pBlock->info.dataLoad = 1;
+  pBlock->info.rows += 1;
+  pScanInfo->lastKey = pTSRow->ts;
+  return TSDB_CODE_SUCCESS;
+}
+
+int32_t doAppendRowFromFileBlock(SSDataBlock* pResBlock, STsdbReader* pReader, SBlockData* pBlockData,
+                                 int32_t rowIndex) {
+  int32_t i = 0, j = 0;
+  int32_t outputRowIndex = pResBlock->info.rows;
+  int32_t code = TSDB_CODE_SUCCESS;
+
+  SBlockLoadSuppInfo* pSupInfo = &pReader->suppInfo;
+  ((int64_t*)pReader->status.pPrimaryTsCol->pData)[outputRowIndex] = pBlockData->aTSKEY[rowIndex];
+  i += 1;
+
+  SColVal cv = {0};
+  int32_t numOfInputCols = pBlockData->nColData;
+  int32_t numOfOutputCols = pSupInfo->numOfCols;
+
+  while (i < numOfOutputCols && j < numOfInputCols) {
+    SColData* pData = tBlockDataGetColDataByIdx(pBlockData, j);
+    if (pData->cid < pSupInfo->colId[i]) {
+      j += 1;
+      continue;
+    }
+
+    SColumnInfoData* pCol = TARRAY_GET_ELEM(pResBlock->pDataBlock, pSupInfo->slotId[i]);
+    if (pData->cid == pSupInfo->colId[i]) {
+      tColDataGetValue(pData, rowIndex, &cv);
+      code = doCopyColVal(pCol, outputRowIndex, i, &cv, pSupInfo);
+      if (code) {
+        return code;
+      }
+      j += 1;
+    } else if (pData->cid > pCol->info.colId) {
+      // the specified column does not exist in file block, fill with null data
+      colDataSetNULL(pCol, outputRowIndex);
+    }
+
+    i += 1;
+  }
+
+  while (i < numOfOutputCols) {
+    SColumnInfoData* pCol = taosArrayGet(pResBlock->pDataBlock, pSupInfo->slotId[i]);
+    colDataSetNULL(pCol, outputRowIndex);
+    i += 1;
+  }
+
+  pResBlock->info.dataLoad = 1;
+  pResBlock->info.rows += 1;
+  return TSDB_CODE_SUCCESS;
+}
+
+int32_t buildDataBlockFromBufImpl(STableBlockScanInfo* pBlockScanInfo, int64_t endKey, int32_t capacity,
+                                  STsdbReader* pReader) {
+  SSDataBlock* pBlock = pReader->resBlockInfo.pResBlock;
+  int32_t      code = TSDB_CODE_SUCCESS;
+
+  do {
+    //    SRow* pTSRow = NULL;
+    TSDBROW row = {.type = -1};
+    bool    freeTSRow = false;
+    tsdbGetNextRowInMem(pBlockScanInfo, pReader, &row, endKey, &freeTSRow);
+    if (row.type == -1) {
+      break;
+    }
+
+    if (row.type == TSDBROW_ROW_FMT) {
+      code = doAppendRowFromTSRow(pBlock, pReader, row.pTSRow, pBlockScanInfo);
+
+      if (freeTSRow) {
+        taosMemoryFree(row.pTSRow);
+      }
+
+      if (code) {
+        return code;
+      }
+    } else {
+      code = doAppendRowFromFileBlock(pBlock, pReader, row.pBlockData, row.iRow);
+      if (code) {
+        break;
+      }
+    }
+
+    // no data in buffer, return immediately
+    if (!(pBlockScanInfo->iter.hasVal || pBlockScanInfo->iiter.hasVal)) {
+      break;
+    }
+
+    if (pBlock->info.rows >= capacity) {
+      break;
+    }
+  } while (1);
+
+  return code;
+}
+
+// TODO refactor: with createDataBlockScanInfo
+int32_t tsdbSetTableList(STsdbReader* pReader, const void* pTableList, int32_t num) {
+  int32_t size = tSimpleHashGetSize(pReader->status.pTableMap);
+
+  STableBlockScanInfo** p = NULL;
+  int32_t iter = 0;
+
+  while ((p = tSimpleHashIterate(pReader->status.pTableMap, p, &iter)) != NULL) {
+    clearBlockScanInfo(*p);
+  }
+
+  if (size < num) {
+    int32_t code = ensureBlockScanInfoBuf(&pReader->blockInfoBuf, num);
+    if (code) {
+      return code;
+    }
+
+    char* p1 = taosMemoryRealloc(pReader->status.uidList.tableUidList, sizeof(uint64_t) * num);
+    if (p1 == NULL) {
+      return TSDB_CODE_OUT_OF_MEMORY;
+    }
+
+    pReader->status.uidList.tableUidList = (uint64_t*)p1;
+  }
+
+  tSimpleHashClear(pReader->status.pTableMap);
+  STableUidList* pUidList = &pReader->status.uidList;
+  pUidList->currentIndex = 0;
+
+  STableKeyInfo* pList = (STableKeyInfo*)pTableList;
+  for (int32_t i = 0; i < num; ++i) {
+    STableBlockScanInfo* pInfo = getPosInBlockInfoBuf(&pReader->blockInfoBuf, i);
+    pInfo->uid = pList[i].uid;
+    pUidList->tableUidList[i] = pList[i].uid;
+
+    // todo extract method
+    if (ASCENDING_TRAVERSE(pReader->order)) {
+      int64_t skey = pReader->window.skey;
+      pInfo->lastKey = (skey > INT64_MIN) ? (skey - 1) : skey;
+      pInfo->lastKeyInStt = skey;
+    } else {
+      int64_t ekey = pReader->window.ekey;
+      pInfo->lastKey = (ekey < INT64_MAX) ? (ekey + 1) : ekey;
+      pInfo->lastKeyInStt = ekey;
+    }
+
+    tSimpleHashPut(pReader->status.pTableMap, &pInfo->uid, sizeof(uint64_t), &pInfo, POINTER_BYTES);
+  }
+
+  return TDB_CODE_SUCCESS;
+}
+
+void* tsdbGetIdx(SMeta* pMeta) {
+  if (pMeta == NULL) {
+    return NULL;
+  }
+  return metaGetIdx(pMeta);
+}
+
+void* tsdbGetIvtIdx(SMeta* pMeta) {
+  if (pMeta == NULL) {
+    return NULL;
+  }
+  return metaGetIvtIdx(pMeta);
+}
+
+uint64_t tsdbGetReaderMaxVersion(STsdbReader* pReader) { return pReader->verRange.maxVer; }
+
+static int32_t doOpenReaderImpl(STsdbReader* pReader) {
+  SReaderStatus*  pStatus = &pReader->status;
+  SDataBlockIter* pBlockIter = &pStatus->blockIter;
+
+  initFilesetIterator(&pStatus->fileIter, pReader->pReadSnap->fs.aDFileSet, pReader);
+  resetDataBlockIterator(&pStatus->blockIter, pReader->order);
+
+  int32_t code = TSDB_CODE_SUCCESS;
+  if (pStatus->fileIter.numOfFiles == 0) {
+    pStatus->loadFromFile = false;
+  } else if (READ_MODE_COUNT_ONLY == pReader->readMode) {
+    // DO NOTHING
+  } else {
+    code = initForFirstBlockInFile(pReader, pBlockIter);
+  }
+
+  if (!pStatus->loadFromFile) {
+    resetTableListIndex(pStatus);
+  }
+
+  return code;
+}
+
+static void freeSchemaFunc(void* param) {
+  void **p = (void **)param;
+  taosMemoryFreeClear(*p);
+}
+
+// ====================================== EXPOSED APIs ======================================
+int32_t tsdbReaderOpen2(void* pVnode, SQueryTableDataCond* pCond, void* pTableList, int32_t numOfTables,
+                       SSDataBlock* pResBlock, void** ppReader, const char* idstr, bool countOnly, SHashObj** pIgnoreTables) {
+  STimeWindow window = pCond->twindows;
+  SVnodeCfg* pConf = &(((SVnode*)pVnode)->config);
+
+  int32_t capacity = pConf->tsdbCfg.maxRows;
+  if (pResBlock != NULL) {
+    blockDataEnsureCapacity(pResBlock, capacity);
+  }
+
+  int32_t code = tsdbReaderCreate(pVnode, pCond, ppReader, capacity, pResBlock, idstr);
+  if (code != TSDB_CODE_SUCCESS) {
+    goto _err;
+  }
+
+  // check for query time window
+  STsdbReader* pReader = *ppReader;
+  if (isEmptyQueryTimeWindow(&pReader->window) && pCond->type == TIMEWINDOW_RANGE_CONTAINED) {
+    tsdbDebug("%p query window not overlaps with the data set, no result returned, %s", pReader, pReader->idStr);
+    return TSDB_CODE_SUCCESS;
+  }
+
+  if (pCond->type == TIMEWINDOW_RANGE_EXTERNAL) {
+    // update the SQueryTableDataCond to create inner reader
+    int32_t order = pCond->order;
+    if (order == TSDB_ORDER_ASC) {
+      pCond->twindows.ekey = window.skey - 1;
+      pCond->twindows.skey = INT64_MIN;
+      pCond->order = TSDB_ORDER_DESC;
+    } else {
+      pCond->twindows.skey = window.ekey + 1;
+      pCond->twindows.ekey = INT64_MAX;
+      pCond->order = TSDB_ORDER_ASC;
+    }
+
+    // here we only need one more row, so the capacity is set to be ONE.
+    code = tsdbReaderCreate(pVnode, pCond, (void**)&((STsdbReader*)pReader)->innerReader[0], 1, pResBlock, idstr);
+    if (code != TSDB_CODE_SUCCESS) {
+      goto _err;
+    }
+
+    if (order == TSDB_ORDER_ASC) {
+      pCond->twindows.skey = window.ekey + 1;
+      pCond->twindows.ekey = INT64_MAX;
+    } else {
+      pCond->twindows.skey = INT64_MIN;
+      pCond->twindows.ekey = window.ekey - 1;
+    }
+    pCond->order = order;
+
+    code = tsdbReaderCreate(pVnode, pCond, (void**)&((STsdbReader*)pReader)->innerReader[1], 1, pResBlock, idstr);
+    if (code != TSDB_CODE_SUCCESS) {
+      goto _err;
+    }
+  }
+
+  // NOTE: the endVersion in pCond is the data version not schema version, so pCond->endVersion is not correct here.
+  //  no valid error code set in metaGetTbTSchema, so let's set the error code here.
+  //  we should proceed in case of tmq processing.
+  if (pCond->suid != 0) {
+    pReader->pSchema = metaGetTbTSchema(pReader->pTsdb->pVnode->pMeta, pReader->suid, -1, 1);
+    if (pReader->pSchema == NULL) {
+      tsdbError("failed to get table schema, suid:%" PRIu64 ", ver:-1, %s", pReader->suid, pReader->idStr);
+    }
+  } else if (numOfTables > 0) {
+    STableKeyInfo* pKey = pTableList;
+    pReader->pSchema = metaGetTbTSchema(pReader->pTsdb->pVnode->pMeta, pKey->uid, -1, 1);
+    if (pReader->pSchema == NULL) {
+      tsdbError("failed to get table schema, uid:%" PRIu64 ", ver:-1, %s", pKey->uid, pReader->idStr);
+    }
+  }
+
+  if (pReader->pSchema != NULL) {
+    tsdbRowMergerInit(&pReader->status.merger, pReader->pSchema);
+  }
+
+  pReader->pSchemaMap = tSimpleHashInit(8, taosFastHash);
+  if (pReader->pSchemaMap == NULL) {
+    tsdbError("failed init schema hash for reader %s", pReader->idStr);
+    code = TSDB_CODE_OUT_OF_MEMORY;
+    goto _err;
+  }
+
+  tSimpleHashSetFreeFp(pReader->pSchemaMap, freeSchemaFunc);
+  if (pReader->pSchema != NULL) {
+    code = updateBlockSMAInfo(pReader->pSchema, &pReader->suppInfo);
+    if (code != TSDB_CODE_SUCCESS) {
+      goto _err;
+    }
+  }
+
+  STsdbReader* p = (pReader->innerReader[0] != NULL) ? pReader->innerReader[0] : pReader;
+  pReader->status.pTableMap =
+      createDataBlockScanInfo(p, &pReader->blockInfoBuf, pTableList, &pReader->status.uidList, numOfTables);
+  if (pReader->status.pTableMap == NULL) {
+    *ppReader = NULL;
+    code = TSDB_CODE_OUT_OF_MEMORY;
+    goto _err;
+  }
+
+  pReader->status.pLDataIter = taosMemoryCalloc(pConf->sttTrigger, sizeof(SLDataIter));
+  if (pReader->status.pLDataIter == NULL) {
+    terrno = TSDB_CODE_OUT_OF_MEMORY;
+    goto _err;
+  }
+
+  pReader->flag = READER_STATUS_SUSPEND;
+
+  if (countOnly) {
+    pReader->readMode = READ_MODE_COUNT_ONLY;
+  }
+
+  pReader->pIgnoreTables = pIgnoreTables;
+
+  tsdbDebug("%p total numOfTable:%d, window:%" PRId64 " - %" PRId64 ", verRange:%" PRId64 " - %" PRId64
+                " in this query %s",
+            pReader, numOfTables, pReader->window.skey, pReader->window.ekey, pReader->verRange.minVer,
+            pReader->verRange.maxVer, pReader->idStr);
+
+  return code;
+
+  _err:
+  tsdbError("failed to create data reader, code:%s %s", tstrerror(code), idstr);
+  tsdbReaderClose(*ppReader);
+  *ppReader = NULL;  // reset the pointer value.
+  return code;
+}
+
+static void clearSharedPtr(STsdbReader* p) {
+  p->status.pLDataIter = NULL;
+  p->status.pTableMap = NULL;
+  p->status.uidList.tableUidList = NULL;
+  p->pReadSnap = NULL;
+  p->pSchema = NULL;
+  p->pSchemaMap = NULL;
+}
+
+static void setSharedPtr(STsdbReader* pDst, const STsdbReader* pSrc) {
+  pDst->status.pTableMap = pSrc->status.pTableMap;
+  pDst->status.pLDataIter = pSrc->status.pLDataIter;
+  pDst->status.uidList = pSrc->status.uidList;
+  pDst->pSchema = pSrc->pSchema;
+  pDst->pSchemaMap = pSrc->pSchemaMap;
+  pDst->pReadSnap = pSrc->pReadSnap;
+
+  if (pDst->pSchema) {
+    tsdbRowMergerInit(&pDst->status.merger, pDst->pSchema);
+  }
+}
+
+void tsdbReaderClose(STsdbReader* pReader) {
+  if (pReader == NULL) {
+    return;
+  }
+
+  tsdbAcquireReader(pReader);
+
+  {
+    if (pReader->innerReader[0] != NULL || pReader->innerReader[1] != NULL) {
+      STsdbReader* p = pReader->innerReader[0];
+      clearSharedPtr(p);
+
+      p = pReader->innerReader[1];
+      clearSharedPtr(p);
+
+      tsdbReaderClose(pReader->innerReader[0]);
+      tsdbReaderClose(pReader->innerReader[1]);
+    }
+  }
+
+  SBlockLoadSuppInfo* pSupInfo = &pReader->suppInfo;
+
+  taosArrayDestroy(pSupInfo->pColAgg);
+  for (int32_t i = 0; i < pSupInfo->numOfCols; ++i) {
+    if (pSupInfo->buildBuf[i] != NULL) {
+      taosMemoryFreeClear(pSupInfo->buildBuf[i]);
+    }
+  }
+
+  if (pReader->resBlockInfo.freeBlock) {
+    pReader->resBlockInfo.pResBlock = blockDataDestroy(pReader->resBlockInfo.pResBlock);
+  }
+
+  taosMemoryFree(pSupInfo->colId);
+  tBlockDataDestroy(&pReader->status.fileBlockData);
+  cleanupDataBlockIterator(&pReader->status.blockIter);
+
+  size_t numOfTables = tSimpleHashGetSize(pReader->status.pTableMap);
+  if (pReader->status.pTableMap != NULL) {
+    destroyAllBlockScanInfo(pReader->status.pTableMap);
+    clearBlockScanInfoBuf(&pReader->blockInfoBuf);
+  }
+
+  if (pReader->pFileReader != NULL) {
+    tsdbDataFReaderClose(&pReader->pFileReader);
+  }
+
+  if (pReader->pDelFReader != NULL) {
+    tsdbDelFReaderClose(&pReader->pDelFReader);
+  }
+
+  if (pReader->pDelIdx != NULL) {
+    taosArrayDestroy(pReader->pDelIdx);
+    pReader->pDelIdx = NULL;
+  }
+
+  qTrace("tsdb/reader-close: %p, untake snapshot", pReader);
+  tsdbUntakeReadSnap(pReader, pReader->pReadSnap, true);
+  pReader->pReadSnap = NULL;
+
+  tsdbReleaseReader(pReader);
+
+  tsdbUninitReaderLock(pReader);
+
+  taosMemoryFreeClear(pReader->status.pLDataIter);
+  taosMemoryFreeClear(pReader->status.uidList.tableUidList);
+  SIOCostSummary* pCost = &pReader->cost;
+
+  SFilesetIter* pFilesetIter = &pReader->status.fileIter;
+  if (pFilesetIter->pLastBlockReader != NULL) {
+    SLastBlockReader* pLReader = pFilesetIter->pLastBlockReader;
+    tMergeTreeClose(&pLReader->mergeTree);
+
+    getLastBlockLoadInfo(pLReader->pInfo, &pCost->lastBlockLoad, &pCost->lastBlockLoadTime);
+
+    pLReader->pInfo = destroyLastBlockLoadInfo(pLReader->pInfo);
+    taosMemoryFree(pLReader);
+  }
+
+  tsdbDebug(
+      "%p :io-cost summary: head-file:%" PRIu64 ", head-file time:%.2f ms, SMA:%" PRId64
+      " SMA-time:%.2f ms, fileBlocks:%" PRId64
+      ", fileBlocks-load-time:%.2f ms, "
+      "build in-memory-block-time:%.2f ms, lastBlocks:%" PRId64 ", lastBlocks-time:%.2f ms, composed-blocks:%" PRId64
+      ", composed-blocks-time:%.2fms, STableBlockScanInfo size:%.2f Kb, createTime:%.2f ms,initDelSkylineIterTime:%.2f "
+      "ms, %s",
+      pReader, pCost->headFileLoad, pCost->headFileLoadTime, pCost->smaDataLoad, pCost->smaLoadTime, pCost->numOfBlocks,
+      pCost->blockLoadTime, pCost->buildmemBlock, pCost->lastBlockLoad, pCost->lastBlockLoadTime, pCost->composedBlocks,
+      pCost->buildComposedBlockTime, numOfTables * sizeof(STableBlockScanInfo) / 1000.0, pCost->createScanInfoList,
+      pCost->initDelSkylineIterTime, pReader->idStr);
+
+  taosMemoryFree(pReader->idStr);
+
+  tsdbRowMergerCleanup(&pReader->status.merger);
+  taosMemoryFree(pReader->pSchema);
+
+  tSimpleHashCleanup(pReader->pSchemaMap);
+  taosMemoryFreeClear(pReader);
+}
+
+int32_t tsdbReaderSuspend(STsdbReader* pReader) {
+  int32_t code = 0;
+
+  // save reader's base state & reset top state to be reconstructed from base state
+  SReaderStatus*       pStatus = &pReader->status;
+  STableBlockScanInfo* pBlockScanInfo = NULL;
+
+  if (pStatus->loadFromFile) {
+    SFileDataBlockInfo* pBlockInfo = getCurrentBlockInfo(&pReader->status.blockIter);
+    if (pBlockInfo != NULL) {
+      pBlockScanInfo = getTableBlockScanInfo(pStatus->pTableMap, pBlockInfo->uid, pReader->idStr);
+      if (pBlockScanInfo == NULL) {
+        goto _err;
+      }
+    } else {
+      pBlockScanInfo = *pStatus->pTableIter;
+    }
+
+    tsdbDataFReaderClose(&pReader->pFileReader);
+
+    // resetDataBlockScanInfo excluding lastKey
+    STableBlockScanInfo** p = NULL;
+    int32_t iter = 0;
+
+    while ((p = tSimpleHashIterate(pStatus->pTableMap, p, &iter)) != NULL) {
+      STableBlockScanInfo* pInfo = *(STableBlockScanInfo**)p;
+
+      pInfo->iterInit = false;
+      pInfo->iter.hasVal = false;
+      pInfo->iiter.hasVal = false;
+
+      if (pInfo->iter.iter != NULL) {
+        pInfo->iter.iter = tsdbTbDataIterDestroy(pInfo->iter.iter);
+      }
+
+      if (pInfo->iiter.iter != NULL) {
+        pInfo->iiter.iter = tsdbTbDataIterDestroy(pInfo->iiter.iter);
+      }
+
+      pInfo->delSkyline = taosArrayDestroy(pInfo->delSkyline);
+    }
+  } else {
+    // resetDataBlockScanInfo excluding lastKey
+    STableBlockScanInfo** p = NULL;
+    int32_t iter = 0;
+
+    while ((p = tSimpleHashIterate(pStatus->pTableMap, p, &iter)) != NULL) {
+      STableBlockScanInfo* pInfo = *(STableBlockScanInfo**)p;
+
+      pInfo->iterInit = false;
+      pInfo->iter.hasVal = false;
+      pInfo->iiter.hasVal = false;
+
+      if (pInfo->iter.iter != NULL) {
+        pInfo->iter.iter = tsdbTbDataIterDestroy(pInfo->iter.iter);
+      }
+
+      if (pInfo->iiter.iter != NULL) {
+        pInfo->iiter.iter = tsdbTbDataIterDestroy(pInfo->iiter.iter);
+      }
+
+      pInfo->delSkyline = taosArrayDestroy(pInfo->delSkyline);
+    }
+
+    pBlockScanInfo = pStatus->pTableIter == NULL ? NULL : *pStatus->pTableIter;
+    if (pBlockScanInfo) {
+      // save lastKey to restore memory iterator
+      STimeWindow w = pReader->resBlockInfo.pResBlock->info.window;
+      pBlockScanInfo->lastKey = ASCENDING_TRAVERSE(pReader->order) ? w.ekey : w.skey;
+
+      // reset current current table's data block scan info,
+      pBlockScanInfo->iterInit = false;
+      pBlockScanInfo->iter.hasVal = false;
+      pBlockScanInfo->iiter.hasVal = false;
+      if (pBlockScanInfo->iter.iter != NULL) {
+        pBlockScanInfo->iter.iter = tsdbTbDataIterDestroy(pBlockScanInfo->iter.iter);
+      }
+
+      if (pBlockScanInfo->iiter.iter != NULL) {
+        pBlockScanInfo->iiter.iter = tsdbTbDataIterDestroy(pBlockScanInfo->iiter.iter);
+      }
+
+      pBlockScanInfo->pBlockList = taosArrayDestroy(pBlockScanInfo->pBlockList);
+      tMapDataClear(&pBlockScanInfo->mapData);
+      // TODO: keep skyline for reuse
+      pBlockScanInfo->delSkyline = taosArrayDestroy(pBlockScanInfo->delSkyline);
+    }
+  }
+
+  tsdbUntakeReadSnap(pReader, pReader->pReadSnap, false);
+  pReader->pReadSnap = NULL;
+  pReader->flag = READER_STATUS_SUSPEND;
+
+  tsdbDebug("reader: %p suspended uid %" PRIu64 " in this query %s", pReader, pBlockScanInfo ? pBlockScanInfo->uid : 0,
+            pReader->idStr);
+  return code;
+
+  _err:
+  tsdbError("failed to suspend data reader, code:%s %s", tstrerror(code), pReader->idStr);
+  return code;
+}
+
+static int32_t tsdbSetQueryReseek(void* pQHandle) {
+  int32_t      code = 0;
+  STsdbReader* pReader = pQHandle;
+
+  code = tsdbTryAcquireReader(pReader);
+  if (code == 0) {
+    if (pReader->flag == READER_STATUS_SUSPEND) {
+      tsdbReleaseReader(pReader);
+      return code;
+    }
+
+    tsdbReaderSuspend(pReader);
+
+    tsdbReleaseReader(pReader);
+
+    return code;
+  } else if (code == EBUSY) {
+    return TSDB_CODE_VND_QUERY_BUSY;
+  } else {
+    terrno = TAOS_SYSTEM_ERROR(code);
+    return TSDB_CODE_FAILED;
+  }
+}
+
+int32_t tsdbReaderResume(STsdbReader* pReader) {
+  int32_t code = 0;
+
+  STableBlockScanInfo** pBlockScanInfo = pReader->status.pTableIter;
+
+  //  restore reader's state
+  //  task snapshot
+  int32_t numOfTables = tSimpleHashGetSize(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;
+    }
+
+    if (pReader->type == TIMEWINDOW_RANGE_CONTAINED) {
+      code = doOpenReaderImpl(pReader);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+    } else {
+      STsdbReader* pPrevReader = pReader->innerReader[0];
+      STsdbReader* pNextReader = pReader->innerReader[1];
+
+      // we need only one row
+      pPrevReader->resBlockInfo.capacity = 1;
+      setSharedPtr(pPrevReader, pReader);
+
+      pNextReader->resBlockInfo.capacity = 1;
+      setSharedPtr(pNextReader, pReader);
+
+      code = doOpenReaderImpl(pPrevReader);
+      if (code != TSDB_CODE_SUCCESS) {
+        return code;
+      }
+    }
+  }
+
+  pReader->flag = READER_STATUS_NORMAL;
+  tsdbDebug("reader: %p resumed uid %" PRIu64 ", numOfTable:%" PRId32 ", in this query %s", pReader,
+            pBlockScanInfo ? (*pBlockScanInfo)->uid : 0, numOfTables, pReader->idStr);
+  return code;
+
+  _err:
+  tsdbError("failed to resume data reader, code:%s %s", tstrerror(code), pReader->idStr);
+  return code;
+}
+
+static bool tsdbReadRowsCountOnly(STsdbReader* pReader) {
+  int32_t      code = TSDB_CODE_SUCCESS;
+  SSDataBlock* pBlock = pReader->resBlockInfo.pResBlock;
+
+  if (pReader->status.loadFromFile == false) {
+    return false;
+  }
+
+  code = readRowsCountFromFiles(pReader);
+  if (code != TSDB_CODE_SUCCESS) {
+    return false;
+  }
+
+  code = readRowsCountFromMem(pReader);
+  if (code != TSDB_CODE_SUCCESS) {
+    return false;
+  }
+
+  pBlock->info.rows = pReader->rowsNum;
+  pBlock->info.id.uid = 0;
+  pBlock->info.dataLoad = 0;
+
+  pReader->rowsNum = 0;
+
+  return pBlock->info.rows > 0;
+}
+
+static int32_t doTsdbNextDataBlock(STsdbReader* pReader, bool* hasNext) {
+  int32_t code = TSDB_CODE_SUCCESS;
+
+  // cleanup the data that belongs to the previous data block
+  SSDataBlock* pBlock = pReader->resBlockInfo.pResBlock;
+  blockDataCleanup(pBlock);
+
+  *hasNext = false;
+
+  SReaderStatus* pStatus = &pReader->status;
+  if (tSimpleHashGetSize(pStatus->pTableMap) == 0) {
+    return code;
+  }
+
+  if (READ_MODE_COUNT_ONLY == pReader->readMode) {
+    return tsdbReadRowsCountOnly(pReader);
+  }
+
+  if (pStatus->loadFromFile) {
+    code = buildBlockFromFiles(pReader);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    if (pBlock->info.rows <= 0) {
+      resetTableListIndex(&pReader->status);
+      code = buildBlockFromBufferSequentially(pReader);
+    }
+  } else {  // no data in files, let's try the buffer
+    code = buildBlockFromBufferSequentially(pReader);
+  }
+
+  *hasNext = pBlock->info.rows > 0;
+
+  return code;
+}
+
+int32_t tsdbNextDataBlock(STsdbReader* pReader, bool* hasNext) {
+  int32_t code = TSDB_CODE_SUCCESS;
+
+  *hasNext = false;
+
+  if (isEmptyQueryTimeWindow(&pReader->window) || pReader->step == EXTERNAL_ROWS_NEXT || pReader->code != TSDB_CODE_SUCCESS) {
+    return (pReader->code != TSDB_CODE_SUCCESS)? pReader->code:code;
+  }
+
+  SReaderStatus* pStatus = &pReader->status;
+
+  code = tsdbAcquireReader(pReader);
+  qTrace("tsdb/read: %p, take read mutex, code: %d", pReader, code);
+
+  if (pReader->flag == READER_STATUS_SUSPEND) {
+    code = tsdbReaderResume(pReader);
+    if (code != TSDB_CODE_SUCCESS) {
+      tsdbReleaseReader(pReader);
+      return code;
+    }
+  }
+
+  if (pReader->innerReader[0] != NULL && pReader->step == 0) {
+    code = doTsdbNextDataBlock(pReader->innerReader[0], hasNext);
+    if (code) {
+      tsdbReleaseReader(pReader);
+      return code;
+    }
+
+    pReader->step = EXTERNAL_ROWS_PREV;
+    if (*hasNext) {
+      pStatus = &pReader->innerReader[0]->status;
+      if (pStatus->composedDataBlock) {
+        qTrace("tsdb/read: %p, unlock read mutex", pReader);
+        tsdbReleaseReader(pReader);
+      }
+
+      return code;
+    }
+  }
+
+  if (pReader->step == EXTERNAL_ROWS_PREV) {
+    // prepare for the main scan
+    code = doOpenReaderImpl(pReader);
+    int32_t step = 1;
+    resetAllDataBlockScanInfo(pReader->status.pTableMap, pReader->innerReader[0]->window.ekey, step);
+
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    pReader->step = EXTERNAL_ROWS_MAIN;
+  }
+
+  code = doTsdbNextDataBlock(pReader, hasNext);
+  if (code != TSDB_CODE_SUCCESS) {
+    tsdbReleaseReader(pReader);
+    return code;
+  }
+
+  if (*hasNext) {
+    if (pStatus->composedDataBlock) {
+      qTrace("tsdb/read: %p, unlock read mutex", pReader);
+      tsdbReleaseReader(pReader);
+    }
+
+    return code;
+  }
+
+  if (pReader->step == EXTERNAL_ROWS_MAIN && pReader->innerReader[1] != NULL) {
+    // prepare for the next row scan
+    int32_t step = -1;
+    code = doOpenReaderImpl(pReader->innerReader[1]);
+    resetAllDataBlockScanInfo(pReader->innerReader[1]->status.pTableMap, pReader->window.ekey, step);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
+    code = doTsdbNextDataBlock(pReader->innerReader[1], hasNext);
+    if (code != TSDB_CODE_SUCCESS) {
+      tsdbReleaseReader(pReader);
+      return code;
+    }
+
+    pReader->step = EXTERNAL_ROWS_NEXT;
+    if (*hasNext) {
+      pStatus = &pReader->innerReader[1]->status;
+      if (pStatus->composedDataBlock) {
+        qTrace("tsdb/read: %p, unlock read mutex", pReader);
+        tsdbReleaseReader(pReader);
+      }
+
+      return code;
+    }
+  }
+
+  qTrace("tsdb/read: %p, unlock read mutex", pReader);
+  tsdbReleaseReader(pReader);
+
+  return code;
+}
+
+static bool doFillNullColSMA(SBlockLoadSuppInfo* pSup, int32_t numOfRows, int32_t numOfCols, SColumnDataAgg* pTsAgg) {
+  bool hasNullSMA = false;
+  // do fill all null column value SMA info
+  int32_t i = 0, j = 0;
+  int32_t size = (int32_t)taosArrayGetSize(pSup->pColAgg);
+  taosArrayInsert(pSup->pColAgg, 0, pTsAgg);
+  size++;
+
+  while (j < numOfCols && i < size) {
+    SColumnDataAgg* pAgg = taosArrayGet(pSup->pColAgg, i);
+    if (pAgg->colId == pSup->colId[j]) {
+      i += 1;
+      j += 1;
+    } else if (pAgg->colId < pSup->colId[j]) {
+      i += 1;
+    } else if (pSup->colId[j] < pAgg->colId) {
+      if (pSup->colId[j] != PRIMARYKEY_TIMESTAMP_COL_ID) {
+        SColumnDataAgg nullColAgg = {.colId = pSup->colId[j], .numOfNull = numOfRows};
+        taosArrayInsert(pSup->pColAgg, i, &nullColAgg);
+        i += 1;
+        size++;
+        hasNullSMA = true;
+      }
+      j += 1;
+    }
+  }
+
+  while (j < numOfCols) {
+    if (pSup->colId[j] != PRIMARYKEY_TIMESTAMP_COL_ID) {
+      SColumnDataAgg nullColAgg = {.colId = pSup->colId[j], .numOfNull = numOfRows};
+      taosArrayInsert(pSup->pColAgg, i, &nullColAgg);
+      i += 1;
+      hasNullSMA = true;
+    }
+    j++;
+  }
+
+  return hasNullSMA;
+}
+
+int32_t tsdbRetrieveDatablockSMA(STsdbReader* pReader, SSDataBlock* pDataBlock, bool* allHave, bool *hasNullSMA) {
+  SColumnDataAgg*** pBlockSMA = &pDataBlock->pBlockAgg;
+
+  int32_t code = 0;
+  *allHave = false;
+  *pBlockSMA = NULL;
+
+  if (pReader->type == TIMEWINDOW_RANGE_EXTERNAL) {
+    return TSDB_CODE_SUCCESS;
+  }
+
+  // there is no statistics data for composed block
+  if (pReader->status.composedDataBlock || (!pReader->suppInfo.smaValid)) {
+    return TSDB_CODE_SUCCESS;
+  }
+
+  SFileDataBlockInfo* pFBlock = getCurrentBlockInfo(&pReader->status.blockIter);
+  SBlockLoadSuppInfo* pSup = &pReader->suppInfo;
+
+  if (pReader->resBlockInfo.pResBlock->info.id.uid != pFBlock->uid) {
+    return TSDB_CODE_SUCCESS;
+  }
+
+  int64_t st = taosGetTimestampUs();
+
+  SDataBlk* pBlock = getCurrentBlock(&pReader->status.blockIter);
+  if (tDataBlkHasSma(pBlock)) {
+    code = tsdbReadBlockSma(pReader->pFileReader, pBlock, pSup->pColAgg);
+    if (code != TSDB_CODE_SUCCESS) {
+      tsdbDebug("vgId:%d, failed to load block SMA for uid %" PRIu64 ", code:%s, %s", 0, pFBlock->uid, tstrerror(code),
+                pReader->idStr);
+      return code;
+    }
+  } else {
+    *pBlockSMA = NULL;
+    return TSDB_CODE_SUCCESS;
+  }
+
+  *allHave = true;
+
+  // always load the first primary timestamp column data
+  SColumnDataAgg* pTsAgg = &pSup->tsColAgg;
+
+  pTsAgg->numOfNull = 0;
+  pTsAgg->colId = PRIMARYKEY_TIMESTAMP_COL_ID;
+  pTsAgg->min = pReader->resBlockInfo.pResBlock->info.window.skey;
+  pTsAgg->max = pReader->resBlockInfo.pResBlock->info.window.ekey;
+
+  // update the number of NULL data rows
+  size_t numOfCols = pSup->numOfCols;
+
+  // ensure capacity
+  if (pDataBlock->pDataBlock) {
+    size_t colsNum = taosArrayGetSize(pDataBlock->pDataBlock);
+    taosArrayEnsureCap(pSup->pColAgg, colsNum);
+  }
+
+  SSDataBlock* pResBlock = pReader->resBlockInfo.pResBlock;
+  if (pResBlock->pBlockAgg == NULL) {
+    size_t num = taosArrayGetSize(pResBlock->pDataBlock);
+    pResBlock->pBlockAgg = taosMemoryCalloc(num, POINTER_BYTES);
+  }
+
+  // do fill all null column value SMA info
+  if (doFillNullColSMA(pSup, pBlock->nRow, numOfCols, pTsAgg)) {
+    *hasNullSMA = true;
+    return TSDB_CODE_SUCCESS;
+  }
+  size_t size = taosArrayGetSize(pSup->pColAgg);
+
+  int32_t i = 0, j = 0;
+  while (j < numOfCols && i < size) {
+    SColumnDataAgg* pAgg = taosArrayGet(pSup->pColAgg, i);
+    if (pAgg->colId == pSup->colId[j]) {
+      pResBlock->pBlockAgg[pSup->slotId[j]] = pAgg;
+      i += 1;
+      j += 1;
+    } else if (pAgg->colId < pSup->colId[j]) {
+      i += 1;
+    } else if (pSup->colId[j] < pAgg->colId) {
+      pResBlock->pBlockAgg[pSup->slotId[j]] = NULL;
+      *allHave = false;
+      j += 1;
+    }
+  }
+
+  *pBlockSMA = pResBlock->pBlockAgg;
+  pReader->cost.smaDataLoad += 1;
+
+  double elapsedTime = (taosGetTimestampUs() - st) / 1000.0;
+  pReader->cost.smaLoadTime += elapsedTime;
+
+  tsdbDebug("vgId:%d, succeed to load block SMA for uid %" PRIu64 ", %s", 0, pFBlock->uid, pReader->idStr);
+  return code;
+}
+
+STableBlockScanInfo* getTableBlockScanInfo(SSHashObj* pTableMap, uint64_t uid, const char* id) {
+  STableBlockScanInfo** p = tSimpleHashGet(pTableMap, &uid, sizeof(uid));
+  if (p == NULL || *p == NULL) {
+    terrno = TSDB_CODE_INVALID_PARA;
+    int32_t size = tSimpleHashGetSize(pTableMap);
+    tsdbError("failed to locate the uid:%" PRIu64 " in query table uid list, total tables:%d, %s", uid, size, id);
+    return NULL;
+  }
+
+  return *p;
+}
+
+static SSDataBlock* doRetrieveDataBlock(STsdbReader* pReader) {
+  SReaderStatus*       pStatus = &pReader->status;
+  int32_t              code = TSDB_CODE_SUCCESS;
+  SFileDataBlockInfo*  pBlockInfo = getCurrentBlockInfo(&pStatus->blockIter);
+
+  if (pReader->code != TSDB_CODE_SUCCESS) {
+    return NULL;
+  }
+
+  STableBlockScanInfo* pBlockScanInfo = getTableBlockScanInfo(pStatus->pTableMap, pBlockInfo->uid, pReader->idStr);
+  if (pBlockScanInfo == NULL) {
+    return NULL;
+  }
+
+  code = doLoadFileBlockData(pReader, &pStatus->blockIter, &pStatus->fileBlockData, pBlockScanInfo->uid);
+  if (code != TSDB_CODE_SUCCESS) {
+    tBlockDataDestroy(&pStatus->fileBlockData);
+    terrno = code;
+    return NULL;
+  }
+
+  code = copyBlockDataToSDataBlock(pReader);
+  if (code != TSDB_CODE_SUCCESS) {
+    tBlockDataDestroy(&pStatus->fileBlockData);
+    terrno = code;
+    return NULL;
+  }
+
+  return pReader->resBlockInfo.pResBlock;
+}
+
+SSDataBlock* tsdbRetrieveDataBlock(STsdbReader* pReader, SArray* pIdList) {
+  STsdbReader* pTReader = pReader;
+  if (pReader->type == TIMEWINDOW_RANGE_EXTERNAL) {
+    if (pReader->step == EXTERNAL_ROWS_PREV) {
+      pTReader = pReader->innerReader[0];
+    } else if (pReader->step == EXTERNAL_ROWS_NEXT) {
+      pTReader = pReader->innerReader[1];
+    }
+  }
+
+  SReaderStatus* pStatus = &pTReader->status;
+  if (pStatus->composedDataBlock) {
+    return pTReader->resBlockInfo.pResBlock;
+  }
+
+  SSDataBlock* ret = doRetrieveDataBlock(pTReader);
+
+  qTrace("tsdb/read-retrieve: %p, unlock read mutex", pReader);
+  tsdbReleaseReader(pReader);
+
+  return ret;
+}
+
+int32_t tsdbReaderReset(STsdbReader* pReader, SQueryTableDataCond* pCond) {
+  int32_t code = TSDB_CODE_SUCCESS;
+
+  qTrace("tsdb/reader-reset: %p, take read mutex", pReader);
+  tsdbAcquireReader(pReader);
+
+  if (pReader->flag == READER_STATUS_SUSPEND) {
+    code = tsdbReaderResume(pReader);
+    if (code != TSDB_CODE_SUCCESS) {
+      tsdbReleaseReader(pReader);
+      return code;
+    }
+  }
+
+  if (isEmptyQueryTimeWindow(&pReader->window) || pReader->pReadSnap == NULL) {
+    tsdbDebug("tsdb reader reset return %p, %s", pReader->pReadSnap, pReader->idStr);
+    tsdbReleaseReader(pReader);
+    return TSDB_CODE_SUCCESS;
+  }
+
+  SReaderStatus*  pStatus = &pReader->status;
+  SDataBlockIter* pBlockIter = &pStatus->blockIter;
+
+  pReader->order = pCond->order;
+  pReader->type = TIMEWINDOW_RANGE_CONTAINED;
+  pStatus->loadFromFile = true;
+  pStatus->pTableIter = NULL;
+  pReader->window = updateQueryTimeWindow(pReader->pTsdb, &pCond->twindows);
+
+  // allocate buffer in order to load data blocks from file
+  memset(&pReader->suppInfo.tsColAgg, 0, sizeof(SColumnDataAgg));
+
+  pReader->suppInfo.tsColAgg.colId = PRIMARYKEY_TIMESTAMP_COL_ID;
+  tsdbDataFReaderClose(&pReader->pFileReader);
+
+  int32_t numOfTables = tSimpleHashGetSize(pStatus->pTableMap);
+
+  initFilesetIterator(&pStatus->fileIter, pReader->pReadSnap->fs.aDFileSet, pReader);
+  resetDataBlockIterator(pBlockIter, pReader->order);
+  resetTableListIndex(&pReader->status);
+
+  bool    asc = ASCENDING_TRAVERSE(pReader->order);
+  int32_t step = asc ? 1 : -1;
+  int64_t ts = asc ? pReader->window.skey - 1 : pReader->window.ekey + 1;
+  resetAllDataBlockScanInfo(pStatus->pTableMap, ts, step);
+
+  // no data in files, let's try buffer in memory
+  if (pStatus->fileIter.numOfFiles == 0) {
+    pStatus->loadFromFile = false;
+    resetTableListIndex(pStatus);
+  } else {
+    code = initForFirstBlockInFile(pReader, pBlockIter);
+    if (code != TSDB_CODE_SUCCESS) {
+      tsdbError("%p reset reader failed, numOfTables:%d, query range:%" PRId64 " - %" PRId64 " in query %s", pReader,
+                numOfTables, pReader->window.skey, pReader->window.ekey, pReader->idStr);
+
+      tsdbReleaseReader(pReader);
+      return code;
+    }
+  }
+
+  tsdbDebug("%p reset reader, suid:%" PRIu64 ", numOfTables:%d, skey:%" PRId64 ", query range:%" PRId64 " - %" PRId64
+                " in query %s",
+            pReader, pReader->suid, numOfTables, pCond->twindows.skey, pReader->window.skey, pReader->window.ekey,
+            pReader->idStr);
+
+  tsdbReleaseReader(pReader);
+
+  return code;
+}
+
+static int32_t getBucketIndex(int32_t startRow, int32_t bucketRange, int32_t numOfRows, int32_t numOfBucket) {
+  if (numOfRows < startRow) {
+    return 0;
+  }
+  int32_t bucketIndex = ((numOfRows - startRow) / bucketRange);
+  if (bucketIndex == numOfBucket) {
+    bucketIndex -= 1;
+  }
+  return bucketIndex;
+}
+
+int32_t tsdbGetFileBlocksDistInfo(STsdbReader* pReader, STableBlockDistInfo* pTableBlockInfo) {
+  int32_t code = TSDB_CODE_SUCCESS;
+  pTableBlockInfo->totalSize = 0;
+  pTableBlockInfo->totalRows = 0;
+  pTableBlockInfo->numOfVgroups = 1;
+
+  const int32_t numOfBuckets = 20.0;
+
+  // find the start data block in file
+  tsdbAcquireReader(pReader);
+  if (pReader->flag == READER_STATUS_SUSPEND) {
+    code = tsdbReaderResume(pReader);
+    if (code != TSDB_CODE_SUCCESS) {
+      tsdbReleaseReader(pReader);
+      return code;
+    }
+  }
+  SReaderStatus* pStatus = &pReader->status;
+
+  STsdbCfg* pc = &pReader->pTsdb->pVnode->config.tsdbCfg;
+  pTableBlockInfo->defMinRows = pc->minRows;
+  pTableBlockInfo->defMaxRows = pc->maxRows;
+
+  int32_t bucketRange = ceil(((double)(pc->maxRows - pc->minRows)) / numOfBuckets);
+
+  pTableBlockInfo->numOfFiles += 1;
+
+  int32_t numOfTables = (int32_t)tSimpleHashGetSize(pStatus->pTableMap);
+  int     defaultRows = 4096;
+
+  SDataBlockIter* pBlockIter = &pStatus->blockIter;
+  pTableBlockInfo->numOfFiles += pStatus->fileIter.numOfFiles;
+
+  if (pBlockIter->numOfBlocks > 0) {
+    pTableBlockInfo->numOfBlocks += pBlockIter->numOfBlocks;
+  }
+
+  pTableBlockInfo->numOfTables = numOfTables;
+  bool hasNext = (pBlockIter->numOfBlocks > 0);
+
+  while (true) {
+    if (hasNext) {
+      SDataBlk* pBlock = getCurrentBlock(pBlockIter);
+
+      int32_t numOfRows = pBlock->nRow;
+      pTableBlockInfo->totalRows += numOfRows;
+
+      if (numOfRows > pTableBlockInfo->maxRows) {
+        pTableBlockInfo->maxRows = numOfRows;
+      }
+
+      if (numOfRows < pTableBlockInfo->minRows) {
+        pTableBlockInfo->minRows = numOfRows;
+      }
+
+      if (numOfRows < defaultRows) {
+        pTableBlockInfo->numOfSmallBlocks += 1;
+      }
+
+      pTableBlockInfo->totalSize += pBlock->aSubBlock[0].szBlock;
+
+      int32_t bucketIndex = getBucketIndex(pTableBlockInfo->defMinRows, bucketRange, numOfRows, numOfBuckets);
+      pTableBlockInfo->blockRowsHisto[bucketIndex]++;
+
+      hasNext = blockIteratorNext(&pStatus->blockIter, pReader->idStr);
+    } else {
+      code = initForFirstBlockInFile(pReader, pBlockIter);
+      if ((code != TSDB_CODE_SUCCESS) || (pStatus->loadFromFile == false)) {
+        break;
+      }
+
+      pTableBlockInfo->numOfBlocks += pBlockIter->numOfBlocks;
+      hasNext = (pBlockIter->numOfBlocks > 0);
+    }
+
+    //    tsdbDebug("%p %d blocks found in file for %d table(s), fid:%d, %s", pReader, numOfBlocks, numOfTables,
+    //              pReader->pFileGroup->fid, pReader->idStr);
+  }
+  tsdbReleaseReader(pReader);
+  return code;
+}
+
+int64_t tsdbGetNumOfRowsInMemTable(STsdbReader* pReader) {
+  int32_t code = TSDB_CODE_SUCCESS;
+  int64_t rows = 0;
+
+  SReaderStatus* pStatus = &pReader->status;
+  tsdbAcquireReader(pReader);
+  if (pReader->flag == READER_STATUS_SUSPEND) {
+    code = tsdbReaderResume(pReader);
+    if (code != TSDB_CODE_SUCCESS) {
+      tsdbReleaseReader(pReader);
+      return code;
+    }
+  }
+
+  int32_t iter = 0;
+  pStatus->pTableIter = tSimpleHashIterate(pStatus->pTableMap, NULL, &iter);
+
+  while (pStatus->pTableIter != NULL) {
+    STableBlockScanInfo* pBlockScanInfo = *(STableBlockScanInfo**)pStatus->pTableIter;
+
+    STbData* d = NULL;
+    if (pReader->pReadSnap->pMem != NULL) {
+      d = tsdbGetTbDataFromMemTable(pReader->pReadSnap->pMem, pReader->suid, pBlockScanInfo->uid);
+      if (d != NULL) {
+        rows += tsdbGetNRowsInTbData(d);
+      }
+    }
+
+    STbData* di = NULL;
+    if (pReader->pReadSnap->pIMem != NULL) {
+      di = tsdbGetTbDataFromMemTable(pReader->pReadSnap->pIMem, pReader->suid, pBlockScanInfo->uid);
+      if (di != NULL) {
+        rows += tsdbGetNRowsInTbData(di);
+      }
+    }
+
+    // current table is exhausted, let's try the next table
+    pStatus->pTableIter = tSimpleHashIterate(pStatus->pTableMap, pStatus->pTableIter, &iter);
+  }
+
+  tsdbReleaseReader(pReader);
+
+  return rows;
+}
+
+int32_t tsdbGetTableSchema(void* pVnode, int64_t uid, STSchema** pSchema, int64_t* suid) {
+  SMetaReader mr = {0};
+  metaReaderInit(&mr, ((SVnode*)pVnode)->pMeta, 0);
+  int32_t code = metaReaderGetTableEntryByUidCache(&mr, uid);
+  if (code != TSDB_CODE_SUCCESS) {
+    terrno = TSDB_CODE_TDB_INVALID_TABLE_ID;
+    metaReaderClear(&mr);
+    return terrno;
+  }
+
+  *suid = 0;
+
+  // only child table and ordinary table is allowed, super table is not allowed.
+  if (mr.me.type == TSDB_CHILD_TABLE) {
+    tDecoderClear(&mr.coder);
+    *suid = mr.me.ctbEntry.suid;
+    code = metaReaderGetTableEntryByUidCache(&mr, *suid);
+    if (code != TSDB_CODE_SUCCESS) {
+      terrno = TSDB_CODE_TDB_INVALID_TABLE_ID;
+      metaReaderClear(&mr);
+      return terrno;
+    }
+  } else if (mr.me.type == TSDB_NORMAL_TABLE) {  // do nothing
+  } else {
+    terrno = TSDB_CODE_INVALID_PARA;
+    metaReaderClear(&mr);
+    return terrno;
+  }
+
+  metaReaderClear(&mr);
+
+  // get the newest table schema version
+  code = metaGetTbTSchemaEx(((SVnode*)pVnode)->pMeta, *suid, uid, -1, pSchema);
+  return code;
+}
+
+int32_t tsdbTakeReadSnap(STsdbReader* pReader, _query_reseek_func_t reseek, STsdbReadSnap** ppSnap) {
+  int32_t        code = 0;
+  //todo add
+#if 0
+  STsdb*         pTsdb = pReader->pTsdb;
+  SVersionRange* pRange = &pReader->verRange;
+
+  // alloc
+  STsdbReadSnap* pSnap = (STsdbReadSnap*)taosMemoryCalloc(1, sizeof(*pSnap));
+  if (pSnap == NULL) {
+    code = TSDB_CODE_OUT_OF_MEMORY;
+    goto _exit;
+  }
+
+  // lock
+  taosThreadRwlockRdlock(&pTsdb->rwLock);
+
+  // take snapshot
+  if (pTsdb->mem && (pRange->minVer <= pTsdb->mem->maxVer && pRange->maxVer >= pTsdb->mem->minVer)) {
+    pSnap->pMem = pTsdb->mem;
+    pSnap->pNode = taosMemoryMalloc(sizeof(*pSnap->pNode));
+    if (pSnap->pNode == NULL) {
+      taosThreadRwlockUnlock(&pTsdb->rwLock);
+      code = TSDB_CODE_OUT_OF_MEMORY;
+      goto _exit;
+    }
+    pSnap->pNode->pQHandle = pReader;
+    pSnap->pNode->reseek = reseek;
+
+    tsdbRefMemTable(pTsdb->mem, pSnap->pNode);
+  }
+
+  if (pTsdb->imem && (pRange->minVer <= pTsdb->imem->maxVer && pRange->maxVer >= pTsdb->imem->minVer)) {
+    pSnap->pIMem = pTsdb->imem;
+    pSnap->pINode = taosMemoryMalloc(sizeof(*pSnap->pINode));
+    if (pSnap->pINode == NULL) {
+      taosThreadRwlockUnlock(&pTsdb->rwLock);
+      code = TSDB_CODE_OUT_OF_MEMORY;
+      goto _exit;
+    }
+    pSnap->pINode->pQHandle = pReader;
+    pSnap->pINode->reseek = reseek;
+
+    tsdbRefMemTable(pTsdb->imem, pSnap->pINode);
+  }
+
+  // fs
+  code = tsdbFSRef(pTsdb, &pSnap->fs);
+  if (code) {
+    taosThreadRwlockUnlock(&pTsdb->rwLock);
+    goto _exit;
+  }
+
+  // unlock
+  taosThreadRwlockUnlock(&pTsdb->rwLock);
+
+  tsdbTrace("vgId:%d, take read snapshot", TD_VID(pTsdb->pVnode));
+
+  _exit:
+  if (code) {
+    *ppSnap = NULL;
+    if (pSnap) {
+      if (pSnap->pNode) taosMemoryFree(pSnap->pNode);
+      if (pSnap->pINode) taosMemoryFree(pSnap->pINode);
+      taosMemoryFree(pSnap);
+    }
+  } else {
+    *ppSnap = pSnap;
+  }
+#endif
+
+  return code;
+}
+
+void tsdbUntakeReadSnap(STsdbReader* pReader, STsdbReadSnap* pSnap, bool proactive) {
+  STsdb* pTsdb = pReader->pTsdb;
+
+  if (pSnap) {
+    if (pSnap->pMem) {
+      tsdbUnrefMemTable(pSnap->pMem, pSnap->pNode, proactive);
+    }
+
+    if (pSnap->pIMem) {
+      tsdbUnrefMemTable(pSnap->pIMem, pSnap->pINode, proactive);
+    }
+
+    tsdbFSUnref(pTsdb, &pSnap->fs);
+    if (pSnap->pNode) taosMemoryFree(pSnap->pNode);
+    if (pSnap->pINode) taosMemoryFree(pSnap->pINode);
+    taosMemoryFree(pSnap);
+  }
+  tsdbTrace("vgId:%d, untake read snapshot", TD_VID(pTsdb->pVnode));
+}
+
+// if failed, do nothing
+void tsdbReaderSetId(STsdbReader* pReader, const char* idstr) {
+  taosMemoryFreeClear(pReader->idStr);
+  pReader->idStr = taosStrdup(idstr);
+}
+
+void tsdbReaderSetCloseFlag(STsdbReader* pReader) { pReader->code = TSDB_CODE_TSC_QUERY_CANCELLED; }