/*
 * 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 "os.h"
#include "tulog.h"
#include "talgo.h"
#include "tutil.h"
#include "tcompare.h"
#include "exception.h"

#include "../../../query/inc/qast.h"  // todo move to common module
#include "../../../query/inc/tlosertree.h"  // todo move to util module
#include "tsdb.h"
#include "tsdbMain.h"

#define EXTRA_BYTES 2
#define ASCENDING_TRAVERSE(o)   (o == TSDB_ORDER_ASC)
#define QH_GET_NUM_OF_COLS(handle) ((size_t)(taosArrayGetSize((handle)->pColumns)))

enum {
  QUERY_RANGE_LESS_EQUAL = 0,
  QUERY_RANGE_GREATER_EQUAL = 1,
};

enum {
  TSDB_QUERY_TYPE_ALL      = 1,
  TSDB_QUERY_TYPE_LAST     = 2,
  TSDB_QUERY_TYPE_EXTERNAL = 3,
};

typedef struct SQueryFilePos {
  int32_t fid;
  int32_t slot;
  int32_t pos;
  int64_t lastKey;
  int32_t rows;
  bool    mixBlock;
  bool    blockCompleted;
  STimeWindow win;
} SQueryFilePos;

typedef struct SDataBlockLoadInfo {
  SFileGroup* fileGroup;
  int32_t     slot;
  int32_t     tid;
  SArray*     pLoadedCols;
} SDataBlockLoadInfo;

typedef struct SLoadCompBlockInfo {
  int32_t tid; /* table tid */
  int32_t fileId;
} SLoadCompBlockInfo;

typedef struct STableCheckInfo {
  STableId      tableId;
  TSKEY         lastKey;
  STable*       pTableObj;
  SCompInfo*    pCompInfo;
  int32_t       compSize;
  int32_t       numOfBlocks;    // number of qualified data blocks not the original blocks
  SDataCols*    pDataCols;
  bool          initBuf;        // whether to initialize the in-memory skip list iterator or not
  SSkipListIterator* iter;      // mem buffer skip list iterator
  SSkipListIterator* iiter;     // imem buffer skip list iterator
} STableCheckInfo;

typedef struct STableBlockInfo {
  SCompBlock*        compBlock;
  STableCheckInfo*   pTableCheckInfo;
//  int32_t            blockIndex;
//  int32_t            groupIdx; /* number of group is less than the total number of tables */
} STableBlockInfo;

typedef struct SBlockOrderSupporter {
  int32_t             numOfTables;
  STableBlockInfo**   pDataBlockInfo;
  int32_t*            blockIndexArray;
  int32_t*            numOfBlocksPerTable;
} SBlockOrderSupporter;

typedef struct STsdbQueryHandle {
  STsdbRepo*     pTsdb;
  SQueryFilePos  cur;              // current position
  int16_t        order;
  STimeWindow    window;           // the primary query time window that applies to all queries
  SDataStatis*   statis;           // query level statistics, only one table block statistics info exists at any time
  int32_t        numOfBlocks;
  SArray*        pColumns;         // column list, SColumnInfoData array list
  bool           locateStart;
  int32_t        outputCapacity;
  int32_t        realNumOfRows;
  SArray*        pTableCheckInfo;  //SArray<STableCheckInfo>
  int32_t        activeIndex;
  bool           checkFiles;       // check file stage
  void*          qinfo;            // query info handle, for debug purpose
  int32_t        type;             // query type: retrieve all data blocks, 2. retrieve only last row, 3. retrieve direct prev|next rows
  SFileGroup*    pFileGroup;
  SFileGroupIter fileIter;
  SRWHelper      rhelper;
  STableBlockInfo* pDataBlockInfo;
  
  SDataBlockLoadInfo dataBlockLoadInfo; /* record current block load information */
  SLoadCompBlockInfo compBlockLoadInfo; /* record current compblock information in SQuery */
} STsdbQueryHandle;

static void changeQueryHandleForLastrowQuery(TsdbQueryHandleT pqHandle);
static void changeQueryHandleForInterpQuery(TsdbQueryHandleT pHandle);
static void doMergeTwoLevelData(STsdbQueryHandle* pQueryHandle, STableCheckInfo* pCheckInfo, SCompBlock* pBlock,
                                   SArray* sa);
static int32_t binarySearchForKey(char* pValue, int num, TSKEY key, int order);
static int tsdbReadRowsFromCache(SSkipListIterator* pIter, STable* pTable, TSKEY maxKey, int maxRowsToRead, TSKEY* skey, TSKEY* ekey,
                                 STsdbQueryHandle* pQueryHandle);

static void tsdbInitDataBlockLoadInfo(SDataBlockLoadInfo* pBlockLoadInfo) {
  pBlockLoadInfo->slot = -1;
  pBlockLoadInfo->tid = -1;
  pBlockLoadInfo->fileGroup = NULL;
}

static void tsdbInitCompBlockLoadInfo(SLoadCompBlockInfo* pCompBlockLoadInfo) {
  pCompBlockLoadInfo->tid = -1;
  pCompBlockLoadInfo->fileId = -1;
}

TsdbQueryHandleT* tsdbQueryTables(TsdbRepoT* tsdb, STsdbQueryCond* pCond, STableGroupInfo* groupList) {
  // todo 1. filter not exist table
  // todo 2. add the reference count for each table that is involved in query

  STsdbQueryHandle* pQueryHandle = calloc(1, sizeof(STsdbQueryHandle));
  pQueryHandle->order       = pCond->order;
  pQueryHandle->window      = pCond->twindow;
  pQueryHandle->pTsdb       = tsdb;
  pQueryHandle->type        = TSDB_QUERY_TYPE_ALL;
  pQueryHandle->cur.fid     = -1;
  pQueryHandle->cur.win     = TSWINDOW_INITIALIZER;
  pQueryHandle->checkFiles  = true;//ASCENDING_TRAVERSE(pQueryHandle->order);
  pQueryHandle->activeIndex = 0;   // current active table index
  pQueryHandle->outputCapacity = ((STsdbRepo*)tsdb)->config.maxRowsPerFileBlock;
  
  tsdbInitReadHelper(&pQueryHandle->rhelper, (STsdbRepo*) tsdb);

  size_t sizeOfGroup = taosArrayGetSize(groupList->pGroupList);
  assert(sizeOfGroup >= 1 && pCond != NULL && pCond->numOfCols > 0);

  // allocate buffer in order to load data blocks from file
  int32_t numOfCols = pCond->numOfCols;
  
  pQueryHandle->statis = calloc(numOfCols, sizeof(SDataStatis));
  pQueryHandle->pColumns = taosArrayInit(numOfCols, sizeof(SColumnInfoData));  // todo: use list instead of array?
  
  for (int32_t i = 0; i < numOfCols; ++i) {
    SColumnInfoData  colInfo = {{0}, 0};
  
    colInfo.info = pCond->colList[i];
    colInfo.pData = calloc(1, EXTRA_BYTES + pQueryHandle->outputCapacity * pCond->colList[i].bytes);
    taosArrayPush(pQueryHandle->pColumns, &colInfo);
    pQueryHandle->statis[i].colId = colInfo.info.colId;
  }
  
  pQueryHandle->pTableCheckInfo = taosArrayInit(groupList->numOfTables, sizeof(STableCheckInfo));
  STsdbMeta* pMeta = tsdbGetMeta(tsdb);
  assert(pMeta != NULL);
  
  for (int32_t i = 0; i < sizeOfGroup; ++i) {
    SArray* group = *(SArray**) taosArrayGet(groupList->pGroupList, i);
    
    size_t gsize = taosArrayGetSize(group);
    assert(gsize > 0);
    
    for (int32_t j = 0; j < gsize; ++j) {
      STableId* id = (STableId*) taosArrayGet(group, j);
      
      STableCheckInfo info = {
          .lastKey = pQueryHandle->window.skey,
          .tableId = *id,
          .pTableObj = tsdbGetTableByUid(pMeta, id->uid),
      };
      
      assert(info.pTableObj != NULL && info.pTableObj->tableId.tid == id->tid);
      taosArrayPush(pQueryHandle->pTableCheckInfo, &info);
    }
  }
  
  tsdbTrace("%p total numOfTable:%d in query", pQueryHandle, taosArrayGetSize(pQueryHandle->pTableCheckInfo));

  tsdbInitDataBlockLoadInfo(&pQueryHandle->dataBlockLoadInfo);
  tsdbInitCompBlockLoadInfo(&pQueryHandle->compBlockLoadInfo);

  return (TsdbQueryHandleT) pQueryHandle;
}

TsdbQueryHandleT tsdbQueryLastRow(TsdbRepoT *tsdb, STsdbQueryCond *pCond, STableGroupInfo *groupList) {
  STsdbQueryHandle *pQueryHandle = (STsdbQueryHandle*) tsdbQueryTables(tsdb, pCond, groupList);
  
  pQueryHandle->type = TSDB_QUERY_TYPE_LAST;
  pQueryHandle->order = TSDB_ORDER_DESC;
  
  changeQueryHandleForLastrowQuery(pQueryHandle);
  return pQueryHandle;
}

SArray* tsdbGetQueriedTableIdList(TsdbQueryHandleT *pHandle) {
  assert(pHandle != NULL);
  
  STsdbQueryHandle *pQueryHandle = (STsdbQueryHandle*) pHandle;
  
  size_t size = taosArrayGetSize(pQueryHandle->pTableCheckInfo);
  SArray* res = taosArrayInit(size, sizeof(STableId));
  
  for(int32_t i = 0; i < size; ++i) {
    STableCheckInfo* pCheckInfo = taosArrayGet(pQueryHandle->pTableCheckInfo, i);
    taosArrayPush(res, &pCheckInfo->tableId);
  }
  
  return res;
}

TsdbQueryHandleT tsdbQueryRowsInExternalWindow(TsdbRepoT *tsdb, STsdbQueryCond* pCond, STableGroupInfo *groupList) {
  STsdbQueryHandle *pQueryHandle = (STsdbQueryHandle*) tsdbQueryTables(tsdb, pCond, groupList);
  
  pQueryHandle->type = TSDB_QUERY_TYPE_EXTERNAL;
//  pQueryHandle->outputCapacity = 2;  // only allowed two rows to be loaded
  
  changeQueryHandleForInterpQuery(pQueryHandle);
  return pQueryHandle;
}

static bool initTableMemIterator(STsdbQueryHandle* pHandle, STableCheckInfo* pCheckInfo) {
  STable* pTable = pCheckInfo->pTableObj;
  assert(pTable != NULL);
  
  if (pCheckInfo->initBuf) {
    return true;
  }
  
  pCheckInfo->initBuf = true;
  int32_t order = pHandle->order;
  
  // no data in buffer, abort
  if (pTable->mem == NULL && pTable->imem == NULL) {
    return false;
  }
  
  assert(pCheckInfo->iter == NULL && pCheckInfo->iiter == NULL);
  
  if (pTable->mem) {
    pCheckInfo->iter = tSkipListCreateIterFromVal(pTable->mem->pData, (const char*) &pCheckInfo->lastKey,
                                                  TSDB_DATA_TYPE_TIMESTAMP, order);
  }
  
  if (pTable->imem) {
    pCheckInfo->iiter = tSkipListCreateIterFromVal(pTable->imem->pData, (const char*) &pCheckInfo->lastKey,
                                                   TSDB_DATA_TYPE_TIMESTAMP, order);
  }
  
  // both iterators are NULL, no data in buffer right now
  if (pCheckInfo->iter == NULL && pCheckInfo->iiter == NULL) {
    return false;
  }
  
  bool memEmpty  = (pCheckInfo->iter == NULL) || (pCheckInfo->iter != NULL && !tSkipListIterNext(pCheckInfo->iter));
  bool imemEmpty = (pCheckInfo->iiter == NULL) || (pCheckInfo->iiter != NULL && !tSkipListIterNext(pCheckInfo->iiter));
  if (memEmpty && imemEmpty) { // buffer is empty
    return false;
  }
  
  if (!memEmpty) {
    SSkipListNode* node = tSkipListIterGet(pCheckInfo->iter);
    assert(node != NULL);
  
    SDataRow row = SL_GET_NODE_DATA(node);
    TSKEY key = dataRowKey(row);  // first timestamp in buffer
    tsdbTrace("%p uid:%" PRId64", tid:%d check data in mem from skey:%" PRId64 ", order:%d, %p", pHandle,
           pCheckInfo->tableId.uid, pCheckInfo->tableId.tid, key, order, pHandle->qinfo);
  } else {
    tsdbTrace("%p uid:%" PRId64 ", tid:%d no data in mem", pHandle, pCheckInfo->tableId.uid, pCheckInfo->tableId.tid);
  }
  
  if (!imemEmpty) {
    SSkipListNode* node = tSkipListIterGet(pCheckInfo->iiter);
    assert(node != NULL);
  
    SDataRow row = SL_GET_NODE_DATA(node);
    TSKEY key = dataRowKey(row);  // first timestamp in buffer
    tsdbTrace("%p uid:%" PRId64", tid:%d check data in imem from skey:%" PRId64 ", order:%d, %p", pHandle,
           pCheckInfo->tableId.uid, pCheckInfo->tableId.tid, key, order, pHandle->qinfo);
  } else {
    tsdbTrace("%p uid:%"PRId64", tid:%d no data in imem", pHandle, pCheckInfo->tableId.uid, pCheckInfo->tableId.tid);
  }
  
  return true;
}

static bool hasMoreDataInCache(STsdbQueryHandle* pHandle) {
  size_t size = taosArrayGetSize(pHandle->pTableCheckInfo);
  assert(pHandle->activeIndex < size && pHandle->activeIndex >= 0 && size >= 1);
  pHandle->cur.fid = -1;
  
  STableCheckInfo* pCheckInfo = taosArrayGet(pHandle->pTableCheckInfo, pHandle->activeIndex);

  STable* pTable = pCheckInfo->pTableObj;
  assert(pTable != NULL);

  // no data in cache, abort
  if (pTable->mem == NULL && pTable->imem == NULL) {
    return false;
  }
  
  if (pCheckInfo->iter == NULL && pTable->mem) {
    pCheckInfo->iter = tSkipListCreateIterFromVal(pTable->mem->pData, (const char*) &pCheckInfo->lastKey,
        TSDB_DATA_TYPE_TIMESTAMP, pHandle->order);
    
    if (pCheckInfo->iter == NULL) {
      return false;
    }
  
    if (!tSkipListIterNext(pCheckInfo->iter)) {  // buffer is empty
      return false;
    }
  }
  
  SSkipListNode* node = tSkipListIterGet(pCheckInfo->iter);
  if (node == NULL) {
    return false;
  }

  SDataRow row = SL_GET_NODE_DATA(node);
  pCheckInfo->lastKey = dataRowKey(row);  // first timestamp in buffer
  tsdbTrace("%p uid:%" PRId64", tid:%d check data in buffer from skey:%" PRId64 ", order:%d, %p", pHandle,
      pCheckInfo->tableId.uid, pCheckInfo->tableId.tid, pCheckInfo->lastKey, pHandle->order, pHandle->qinfo);
  
  // all data in mem are checked already.
  if ((pCheckInfo->lastKey > pHandle->window.ekey && ASCENDING_TRAVERSE(pHandle->order)) ||
      (pCheckInfo->lastKey < pHandle->window.ekey && !ASCENDING_TRAVERSE(pHandle->order))) {
    return false;
  }
  
  int32_t step = ASCENDING_TRAVERSE(pHandle->order)? 1:-1;
  STimeWindow* win = &pHandle->cur.win;
  pHandle->cur.rows = tsdbReadRowsFromCache(pCheckInfo->iter, pCheckInfo->pTableObj, pHandle->window.ekey,
                                    pHandle->outputCapacity, &win->skey, &win->ekey, pHandle);  // todo refactor API
  
  // update the last key value
  pCheckInfo->lastKey = win->ekey + step;
  pHandle->cur.lastKey = win->ekey + step;
  pHandle->cur.mixBlock = true;

  if (!ASCENDING_TRAVERSE(pHandle->order)) {
    SWAP(win->skey, win->ekey, TSKEY);
  }
  
  return true;
}

static int32_t getFileIdFromKey(TSKEY key, int32_t daysPerFile, int32_t precision) {
  assert(precision >= TSDB_TIME_PRECISION_MICRO || precision <= TSDB_TIME_PRECISION_NANO);
  if (key == TSKEY_INITIAL_VAL) {
    return INT32_MIN;
  }
  
  int64_t fid = (int64_t)(key / (daysPerFile * tsMsPerDay[precision]));  // set the starting fileId
  if (fid < 0L && llabs(fid) > INT32_MAX) { // data value overflow for INT32
    fid = INT32_MIN;
  }
  
  if (fid > 0L && fid > INT32_MAX) {
    fid = INT32_MAX;
  }
  
  return fid;
}

static int32_t binarySearchForBlockImpl(SCompBlock* pBlock, int32_t numOfBlocks, TSKEY skey, int32_t order) {
  int32_t firstSlot = 0;
  int32_t lastSlot = numOfBlocks - 1;
  
  int32_t midSlot = firstSlot;
  
  while (1) {
    numOfBlocks = lastSlot - firstSlot + 1;
    midSlot = (firstSlot + (numOfBlocks >> 1));
    
    if (numOfBlocks == 1) break;
    
    if (skey > pBlock[midSlot].keyLast) {
      if (numOfBlocks == 2) break;
      if ((order == TSDB_ORDER_DESC) && (skey < pBlock[midSlot + 1].keyFirst)) break;
      firstSlot = midSlot + 1;
    } else if (skey < pBlock[midSlot].keyFirst) {
      if ((order == TSDB_ORDER_ASC) && (skey > pBlock[midSlot - 1].keyLast)) break;
      lastSlot = midSlot - 1;
    } else {
      break;  // got the slot
    }
  }
  
  return midSlot;
}

static int32_t getFileCompInfo(STsdbQueryHandle* pQueryHandle, int32_t* numOfBlocks, int32_t type) {
  // todo check open file failed
  SFileGroup* fileGroup = pQueryHandle->pFileGroup;
  
  assert(fileGroup->files[TSDB_FILE_TYPE_HEAD].fname > 0);
  tsdbSetAndOpenHelperFile(&pQueryHandle->rhelper, fileGroup);

  // load all the comp offset value for all tables in this file
  *numOfBlocks = 0;
  size_t numOfTables = taosArrayGetSize(pQueryHandle->pTableCheckInfo);

  for (int32_t i = 0; i < numOfTables; ++i) {
    STableCheckInfo* pCheckInfo = taosArrayGet(pQueryHandle->pTableCheckInfo, i);

    SCompIdx* compIndex = &pQueryHandle->rhelper.pCompIdx[pCheckInfo->tableId.tid];
    if (compIndex->len == 0 || compIndex->numOfBlocks == 0 ||
        compIndex->uid != pCheckInfo->tableId.uid) {  // no data block in this file, try next file
      pCheckInfo->numOfBlocks = 0;
      continue;  // no data blocks in the file belongs to pCheckInfo->pTable
    } else {
      if (pCheckInfo->compSize < compIndex->len) {
        assert(compIndex->len > 0);
        
        char* t = realloc(pCheckInfo->pCompInfo, compIndex->len);
        assert(t != NULL);
        
        pCheckInfo->pCompInfo = (SCompInfo*) t;
        pCheckInfo->compSize = compIndex->len;
      }
      
      tsdbSetHelperTable(&pQueryHandle->rhelper, pCheckInfo->pTableObj, pQueryHandle->pTsdb);

      tsdbLoadCompInfo(&(pQueryHandle->rhelper), (void *)(pCheckInfo->pCompInfo));
      SCompInfo* pCompInfo = pCheckInfo->pCompInfo;
      
      TSKEY s = MIN(pCheckInfo->lastKey, pQueryHandle->window.ekey);
      TSKEY e = MAX(pCheckInfo->lastKey, pQueryHandle->window.ekey);
      
      // discard the unqualified data block based on the query time window
      int32_t start = binarySearchForBlockImpl(pCompInfo->blocks, compIndex->numOfBlocks, s, TSDB_ORDER_ASC);
      int32_t end = start;
      
      if (s > pCompInfo->blocks[start].keyLast) {
        continue;
      }

      // todo speedup the procedure of located end block
      while (end < compIndex->numOfBlocks && (pCompInfo->blocks[end].keyFirst <= e)) {
        end += 1;
      }

      pCheckInfo->numOfBlocks = (end - start);
      
      if (start > 0) {
        memmove(pCompInfo->blocks, &pCompInfo->blocks[start], pCheckInfo->numOfBlocks * sizeof(SCompBlock));
      }

      (*numOfBlocks) += pCheckInfo->numOfBlocks;
    }
  }

  return TSDB_CODE_SUCCESS;
}

static SDataBlockInfo getTrueDataBlockInfo(STableCheckInfo* pCheckInfo, SCompBlock* pBlock) {
  SDataBlockInfo info = {
      .window = {.skey = pBlock->keyFirst, .ekey = pBlock->keyLast},
      .numOfCols = pBlock->numOfCols,
      .rows = pBlock->numOfRows,
      .tid = pCheckInfo->tableId.tid,
      .uid = pCheckInfo->tableId.uid,
  };

  return info;
}

static SArray* getColumnIdList(STsdbQueryHandle* pQueryHandle) {
  size_t numOfCols = QH_GET_NUM_OF_COLS(pQueryHandle);
  assert(numOfCols <= TSDB_MAX_COLUMNS);
  
  SArray* pIdList = taosArrayInit(numOfCols, sizeof(int16_t));
  for (int32_t i = 0; i < numOfCols; ++i) {
    SColumnInfoData* pCol = taosArrayGet(pQueryHandle->pColumns, i);
    taosArrayPush(pIdList, &pCol->info.colId);
  }
  
  return pIdList;
}

static SArray* getDefaultLoadColumns(STsdbQueryHandle* pQueryHandle, bool loadTS) {
  SArray* pLocalIdList = getColumnIdList(pQueryHandle);
  
  // check if the primary time stamp column needs to load
  int16_t colId = *(int16_t*)taosArrayGet(pLocalIdList, 0);
  
  // the primary timestamp column does not be included in the the specified load column list, add it
  if (loadTS && colId != 0) {
    int16_t columnId = 0;
    taosArrayInsert(pLocalIdList, 0, &columnId);
  }
  
  return pLocalIdList;
}

static bool doLoadFileDataBlock(STsdbQueryHandle* pQueryHandle, SCompBlock* pBlock, STableCheckInfo* pCheckInfo) {
  STsdbRepo *pRepo = pQueryHandle->pTsdb;
  SCompData* data = calloc(1, sizeof(SCompData) + sizeof(SCompCol) * pBlock->numOfCols);

  data->numOfCols = pBlock->numOfCols;
  data->uid = pCheckInfo->pTableObj->tableId.uid;

  bool    blockLoaded = false;
  SArray* sa = getDefaultLoadColumns(pQueryHandle, true);

  if (pCheckInfo->pDataCols == NULL) {
    STsdbMeta* pMeta = tsdbGetMeta(pRepo);
    pCheckInfo->pDataCols = tdNewDataCols(pMeta->maxRowBytes, pMeta->maxCols, pRepo->config.maxRowsPerFileBlock);
  }

  tdInitDataCols(pCheckInfo->pDataCols, tsdbGetTableSchema(tsdbGetMeta(pQueryHandle->pTsdb), pCheckInfo->pTableObj));

  if (tsdbLoadBlockData(&(pQueryHandle->rhelper), pBlock, NULL) == 0) {
    SDataBlockLoadInfo* pBlockLoadInfo = &pQueryHandle->dataBlockLoadInfo;

    pBlockLoadInfo->fileGroup = pQueryHandle->pFileGroup;
    pBlockLoadInfo->slot = pQueryHandle->cur.slot;
    pBlockLoadInfo->tid = pCheckInfo->pTableObj->tableId.tid;

    blockLoaded = true;
  }

  taosArrayDestroy(sa);
  tfree(data);

  return blockLoaded;
}

static void handleDataMergeIfNeeded(STsdbQueryHandle* pQueryHandle, SCompBlock* pBlock, STableCheckInfo* pCheckInfo){
  SQueryFilePos* cur = &pQueryHandle->cur;
  SDataBlockInfo binfo = getTrueDataBlockInfo(pCheckInfo, pBlock);
  /*bool hasData = */ initTableMemIterator(pQueryHandle, pCheckInfo);
  
  TSKEY k1 = TSKEY_INITIAL_VAL, k2 = TSKEY_INITIAL_VAL;
  if (pCheckInfo->iter != NULL && tSkipListIterGet(pCheckInfo->iter) != NULL) {
    SSkipListNode* node = tSkipListIterGet(pCheckInfo->iter);
    
    SDataRow row = SL_GET_NODE_DATA(node);
    k1 = dataRowKey(row);
    
    if (k1 == binfo.window.skey) {
      if (tSkipListIterNext(pCheckInfo->iter)) {
        node = tSkipListIterGet(pCheckInfo->iter);
        row = SL_GET_NODE_DATA(node);
        k1 = dataRowKey(row);
      } else {
        k1 = TSKEY_INITIAL_VAL;
      }
    }
  }
  
  if (pCheckInfo->iiter != NULL && tSkipListIterGet(pCheckInfo->iiter) != NULL) {
    SSkipListNode* node = tSkipListIterGet(pCheckInfo->iiter);
    
    SDataRow row = SL_GET_NODE_DATA(node);
    k2 = dataRowKey(row);
    
    if (k2 == binfo.window.skey) {
      if (tSkipListIterNext(pCheckInfo->iiter)) {
        node = tSkipListIterGet(pCheckInfo->iiter);
        row = SL_GET_NODE_DATA(node);
        k2 = dataRowKey(row);
      } else {
        k2 = TSKEY_INITIAL_VAL;
      }
    }
  }
  
  cur->pos = ASCENDING_TRAVERSE(pQueryHandle->order)? 0:(binfo.rows-1);
  
  if ((ASCENDING_TRAVERSE(pQueryHandle->order) &&
      ((k1 != TSKEY_INITIAL_VAL && k1 <= binfo.window.ekey) || (k2 != TSKEY_INITIAL_VAL && k2 <= binfo.window.ekey))) ||
      (!ASCENDING_TRAVERSE(pQueryHandle->order) &&
      ((k1 != TSKEY_INITIAL_VAL && k1 >= binfo.window.skey) || (k2 != TSKEY_INITIAL_VAL && k2 >= binfo.window.skey)))) {
    
    if ((ASCENDING_TRAVERSE(pQueryHandle->order) &&
    ((k1 != TSKEY_INITIAL_VAL && k1 < binfo.window.skey) || (k2 != TSKEY_INITIAL_VAL && k2 < binfo.window.skey))) ||
        (!ASCENDING_TRAVERSE(pQueryHandle->order) &&
         (((k1 != TSKEY_INITIAL_VAL && k1 > binfo.window.skey) || (k2 != TSKEY_INITIAL_VAL && k2 > binfo.window.skey))))) {
      // do not load file block into buffer
      int32_t step = ASCENDING_TRAVERSE(pQueryHandle->order) ? 1 : -1;

      cur->rows = tsdbReadRowsFromCache(pCheckInfo->iter, pCheckInfo->pTableObj, binfo.window.skey - step,
                                        pQueryHandle->outputCapacity, &cur->win.skey, &cur->win.ekey, pQueryHandle);
      pQueryHandle->realNumOfRows = cur->rows;

      // update the last key value
      pCheckInfo->lastKey = cur->win.ekey + step;
      if (!ASCENDING_TRAVERSE(pQueryHandle->order)) {
        SWAP(cur->win.skey, cur->win.ekey, TSKEY);
      }
      
      cur->mixBlock = true;
      cur->blockCompleted = false;
      return;
    }
  
    SArray* sa = getDefaultLoadColumns(pQueryHandle, true);
  
    doLoadFileDataBlock(pQueryHandle, pBlock, pCheckInfo);
    doMergeTwoLevelData(pQueryHandle, pCheckInfo, pBlock, sa);
    taosArrayDestroy(sa);
    
  } else {
    /*
     * no data in cache, only load data from file
     * during the query processing, data in cache will not be checked anymore.
     *
     * Here the buffer is not enough, so only part of file block can be loaded into memory buffer
     */
    assert(pQueryHandle->outputCapacity >= binfo.rows);
    pQueryHandle->realNumOfRows = binfo.rows;

    cur->rows = binfo.rows;
    cur->win  = binfo.window;
    cur->mixBlock = false;
    cur->blockCompleted = true;
    cur->lastKey = binfo.window.ekey + (ASCENDING_TRAVERSE(pQueryHandle->order)? 1:-1);
  }
}

static bool loadFileDataBlock(STsdbQueryHandle* pQueryHandle, SCompBlock* pBlock, STableCheckInfo* pCheckInfo) {
  SArray*        sa = getDefaultLoadColumns(pQueryHandle, true);
  SQueryFilePos* cur = &pQueryHandle->cur;

  if (ASCENDING_TRAVERSE(pQueryHandle->order)) {
    // query ended in current block
    if (pQueryHandle->window.ekey < pBlock->keyLast || pCheckInfo->lastKey > pBlock->keyFirst) {
      if (!doLoadFileDataBlock(pQueryHandle, pBlock, pCheckInfo)) {
        return false;
      }
  
      SDataCols* pTSCol = pQueryHandle->rhelper.pDataCols[0];
      assert(pTSCol->cols->type == TSDB_DATA_TYPE_TIMESTAMP && pTSCol->numOfRows == pBlock->numOfRows);
      
      if (pCheckInfo->lastKey > pBlock->keyFirst) {
        cur->pos =
            binarySearchForKey(pTSCol->cols[0].pData, pBlock->numOfRows, pCheckInfo->lastKey, pQueryHandle->order);
      } else {
        cur->pos = 0;
      }
      
      doMergeTwoLevelData(pQueryHandle, pCheckInfo, pBlock, sa);
    } else {  // the whole block is loaded in to buffer
      handleDataMergeIfNeeded(pQueryHandle, pBlock, pCheckInfo);
    }
  } else {  //desc order, query ended in current block
    if (pQueryHandle->window.ekey > pBlock->keyFirst || pCheckInfo->lastKey < pBlock->keyLast) {
      if (!doLoadFileDataBlock(pQueryHandle, pBlock, pCheckInfo)) {
        return false;
      }
  
      SDataCols* pTSCol = pQueryHandle->rhelper.pDataCols[0];
      if (pCheckInfo->lastKey < pBlock->keyLast) {
        cur->pos = binarySearchForKey(pTSCol->cols[0].pData, pBlock->numOfRows, pCheckInfo->lastKey, pQueryHandle->order);
      } else {
        cur->pos = pBlock->numOfRows - 1;
      }
      
      doMergeTwoLevelData(pQueryHandle, pCheckInfo, pBlock, sa);
    } else {
      handleDataMergeIfNeeded(pQueryHandle, pBlock, pCheckInfo);
    }
  }

  taosArrayDestroy(sa);
  return pQueryHandle->realNumOfRows > 0;
}

static int vnodeBinarySearchKey(char* pValue, int num, TSKEY key, int order) {
  int    firstPos, lastPos, midPos = -1;
  int    numOfRows;
  TSKEY* keyList;

  assert(order == TSDB_ORDER_ASC || order == TSDB_ORDER_DESC);
  
  if (num <= 0) return -1;

  keyList = (TSKEY*)pValue;
  firstPos = 0;
  lastPos = num - 1;

  if (order == TSDB_ORDER_DESC) {
    // find the first position which is smaller than the key
    while (1) {
      if (key >= keyList[lastPos]) return lastPos;
      if (key == keyList[firstPos]) return firstPos;
      if (key < keyList[firstPos]) return firstPos - 1;

      numOfRows = lastPos - firstPos + 1;
      midPos = (numOfRows >> 1) + firstPos;

      if (key < keyList[midPos]) {
        lastPos = midPos - 1;
      } else if (key > keyList[midPos]) {
        firstPos = midPos + 1;
      } else {
        break;
      }
    }

  } else {
    // find the first position which is bigger than the key
    while (1) {
      if (key <= keyList[firstPos]) return firstPos;
      if (key == keyList[lastPos]) return lastPos;

      if (key > keyList[lastPos]) {
        lastPos = lastPos + 1;
        if (lastPos >= num)
          return -1;
        else
          return lastPos;
      }

      numOfRows = lastPos - firstPos + 1;
      midPos = (numOfRows >> 1) + firstPos;

      if (key < keyList[midPos]) {
        lastPos = midPos - 1;
      } else if (key > keyList[midPos]) {
        firstPos = midPos + 1;
      } else {
        break;
      }
    }
  }

  return midPos;
}

static int32_t copyDataFromFileBlock(STsdbQueryHandle* pQueryHandle, int32_t capacity, int32_t numOfRows, int32_t start, int32_t end) {
  char* pData = NULL;
  int32_t step = ASCENDING_TRAVERSE(pQueryHandle->order)? 1 : -1;
  
  SDataCols* pCols = pQueryHandle->rhelper.pDataCols[0];
  TSKEY* tsArray = pCols->cols[0].pData;
  
  int32_t num = end - start + 1;
  int32_t requiredNumOfCols = taosArrayGetSize(pQueryHandle->pColumns);
  
  //data in buffer has greater timestamp, copy data in file block
  for (int32_t i = 0; i < requiredNumOfCols; ++i) {
    SColumnInfoData* pColInfo = taosArrayGet(pQueryHandle->pColumns, i);
    int32_t          bytes = pColInfo->info.bytes;
    
    if (ASCENDING_TRAVERSE(pQueryHandle->order)) {
      pData = pColInfo->pData + numOfRows * pColInfo->info.bytes;
    } else {
      pData = pColInfo->pData + (capacity - numOfRows - num) * pColInfo->info.bytes;
    }
    
    for (int32_t j = 0; j < pCols->numOfCols; ++j) {  // todo opt performance
      SDataCol* src = &pCols->cols[j];
      
      if (pColInfo->info.colId == src->colId) {
        
        if (pColInfo->info.type != TSDB_DATA_TYPE_BINARY && pColInfo->info.type != TSDB_DATA_TYPE_NCHAR) {
          memmove(pData, src->pData + bytes * start, bytes * num);
        } else {  // handle the var-string
          char* dst = pData;
          
          // todo refactor, only copy one-by-one
          for (int32_t k = start; k < num + start; ++k) {
            char* p = tdGetColDataOfRow(src, k);
            memcpy(dst, p, varDataTLen(p));
            dst += bytes;
          }
        }
        
        break;
      }
    }
  }
  
  pQueryHandle->cur.win.ekey = tsArray[end];
  pQueryHandle->cur.lastKey = tsArray[end] + step;
  
  return numOfRows + num;
}

static void copyOneRowFromMem(STsdbQueryHandle* pQueryHandle, STableCheckInfo* pCheckInfo, int32_t capacity,
    int32_t numOfRows, SDataRow row, STSchema* pSchema) {
  int32_t numOfCols = taosArrayGetSize(pQueryHandle->pColumns);
  int32_t numOfTableCols = schemaNCols(pSchema);
  
  char* pData = NULL;
  for (int32_t i = 0; i < numOfCols; ++i) {
    SColumnInfoData* pColInfo = taosArrayGet(pQueryHandle->pColumns, i);
    
    if (ASCENDING_TRAVERSE(pQueryHandle->order)) {
      pData = pColInfo->pData + numOfRows * pColInfo->info.bytes;
    } else {
      pData = pColInfo->pData + (capacity - numOfRows - 1) * pColInfo->info.bytes;
    }
    
    int32_t offset = 0;
    for (int32_t j = 0; j < numOfTableCols; ++j) {
      if (pColInfo->info.colId == pSchema->columns[j].colId) {
        offset = pSchema->columns[j].offset;
        break;
      }
    }
    
    assert(offset != -1);  // todo handle error
    void* value = tdGetRowDataOfCol(row, pColInfo->info.type, TD_DATA_ROW_HEAD_SIZE + offset);
    
    if (pColInfo->info.type == TSDB_DATA_TYPE_BINARY || pColInfo->info.type == TSDB_DATA_TYPE_NCHAR) {
      memcpy(pData, value, varDataTLen(value));
    } else {
      memcpy(pData, value, pColInfo->info.bytes);
    }
  }
}

// only return the qualified data to client in terms of query time window, data rows in the same block but do not
// be included in the query time window will be discarded
static void doMergeTwoLevelData(STsdbQueryHandle* pQueryHandle, STableCheckInfo* pCheckInfo, SCompBlock* pBlock,
                                  SArray* sa) {
  SQueryFilePos* cur = &pQueryHandle->cur;
  SDataBlockInfo blockInfo = getTrueDataBlockInfo(pCheckInfo, pBlock);
  
  initTableMemIterator(pQueryHandle, pCheckInfo);
  SDataCols* pCols = pQueryHandle->rhelper.pDataCols[0];
  
  int32_t endPos = cur->pos;
  if (ASCENDING_TRAVERSE(pQueryHandle->order) && pQueryHandle->window.ekey > blockInfo.window.ekey) {
    endPos = blockInfo.rows - 1;
    cur->mixBlock = (cur->pos != 0);
  } else if (!ASCENDING_TRAVERSE(pQueryHandle->order) && pQueryHandle->window.ekey < blockInfo.window.skey) {
    endPos = 0;
    cur->mixBlock = (cur->pos != blockInfo.rows - 1);
  } else {
    int32_t order = (pQueryHandle->order == TSDB_ORDER_ASC)? TSDB_ORDER_DESC:TSDB_ORDER_ASC;
    endPos = vnodeBinarySearchKey(pCols->cols[0].pData, pCols->numOfRows, pQueryHandle->window.ekey, order);
    cur->mixBlock = true;
  }
  
  // compared with the data from in-memory buffer, to generate the correct timestamp array list
  int32_t pos = cur->pos;
  
  assert(pCols->cols[0].type == TSDB_DATA_TYPE_TIMESTAMP && pCols->cols[0].colId == 0);
  TSKEY* tsArray = pCols->cols[0].pData;
  
  int32_t numOfRows = 0;
  pQueryHandle->cur.win = TSWINDOW_INITIALIZER;
  int32_t step = ASCENDING_TRAVERSE(pQueryHandle->order)? 1:-1;
  
  // no data in buffer, load data from file directly
  if (pCheckInfo->iiter == NULL && pCheckInfo->iter == NULL) {
    int32_t start = cur->pos;
    int32_t end = endPos;
    if (!ASCENDING_TRAVERSE(pQueryHandle->order)) {
      end = cur->pos;
      start = endPos;
    }
    
    cur->win.skey = tsArray[start];
    cur->win.ekey = tsArray[end];
    
    // todo opt in case of no data in buffer
    numOfRows = copyDataFromFileBlock(pQueryHandle, pQueryHandle->outputCapacity, numOfRows, start, end);
    
      // if the buffer is not full in case of descending order query, move the data in the front of the buffer
    if (!ASCENDING_TRAVERSE(pQueryHandle->order) && numOfRows < pQueryHandle->outputCapacity) {
      int32_t emptySize = pQueryHandle->outputCapacity - numOfRows;
      int32_t reqNumOfCols = taosArrayGetSize(pQueryHandle->pColumns);
  
      for(int32_t i = 0; i < reqNumOfCols; ++i) {
        SColumnInfoData* pColInfo = taosArrayGet(pQueryHandle->pColumns, i);
        memmove(pColInfo->pData, pColInfo->pData + emptySize * pColInfo->info.bytes, numOfRows * pColInfo->info.bytes);
      }
    }
  
    pos += (end - start + 1) * step;
    cur->blockCompleted = (((pos >= endPos || cur->lastKey > pQueryHandle->window.ekey) && ASCENDING_TRAVERSE(pQueryHandle->order)) ||
        ((pos <= endPos || cur->lastKey < pQueryHandle->window.ekey) && !ASCENDING_TRAVERSE(pQueryHandle->order)));
    
    pCheckInfo->lastKey = cur->lastKey;
    pQueryHandle->realNumOfRows = numOfRows;
    cur->rows = numOfRows;
    return;
  } else if (pCheckInfo->iter != NULL && pCheckInfo->iiter == NULL) {
    //  } else if (pCheckInfo->iter == NULL && pCheckInfo->iiter != NULL) {
    //  } else { // iter and iiter are all not NULL, three-way merge data block
    STSchema* pSchema = tsdbGetTableSchema(tsdbGetMeta(pQueryHandle->pTsdb), pCheckInfo->pTableObj);
    SSkipListNode* node = NULL;
    
    do {
      node = tSkipListIterGet(pCheckInfo->iter);
      if (node == NULL) {
        break;
      }

      SDataRow row = SL_GET_NODE_DATA(node);
      TSKEY    key = dataRowKey(row);
      if ((key > pQueryHandle->window.ekey && ASCENDING_TRAVERSE(pQueryHandle->order)) ||
          (key < pQueryHandle->window.ekey && !ASCENDING_TRAVERSE(pQueryHandle->order))) {
        break;
      }

      if (((tsArray[pos] > pQueryHandle->window.ekey || pos > endPos) && ASCENDING_TRAVERSE(pQueryHandle->order)) ||
          ((tsArray[pos] < pQueryHandle->window.ekey || pos < endPos) && !ASCENDING_TRAVERSE(pQueryHandle->order))) {
        break;
      }

      if ((key < tsArray[pos] && ASCENDING_TRAVERSE(pQueryHandle->order)) ||
          (key > tsArray[pos] && !ASCENDING_TRAVERSE(pQueryHandle->order))) {
        copyOneRowFromMem(pQueryHandle, pCheckInfo, pQueryHandle->outputCapacity, numOfRows, row, pSchema);
        numOfRows += 1;
        if (cur->win.skey == TSKEY_INITIAL_VAL) {
          cur->win.skey = key;
        }

        cur->win.ekey = key;
        cur->lastKey  = key + step;
        cur->mixBlock = true;

        tSkipListIterNext(pCheckInfo->iter);
      } else if (key == tsArray[pos]) {  // data in buffer has the same timestamp of data in file block, ignore it
        tSkipListIterNext(pCheckInfo->iter);
      } else if ((key > tsArray[pos] && ASCENDING_TRAVERSE(pQueryHandle->order)) ||
                  (key < tsArray[pos] && !ASCENDING_TRAVERSE(pQueryHandle->order))) {
        if (cur->win.skey == TSKEY_INITIAL_VAL) {
          cur->win.skey = tsArray[pos];
        }

        int32_t order = ASCENDING_TRAVERSE(pQueryHandle->order) ? TSDB_ORDER_DESC : TSDB_ORDER_ASC;
        int32_t end = vnodeBinarySearchKey(pCols->cols[0].pData, pCols->numOfRows, key, order);
        if (tsArray[end] == key) { // the value of key in cache equals to the end timestamp value, ignore it
          tSkipListIterNext(pCheckInfo->iter);
        }
        
        int32_t start = -1;
        if (ASCENDING_TRAVERSE(pQueryHandle->order)) {
          int32_t remain = end - pos + 1;
          if (remain + numOfRows > pQueryHandle->outputCapacity) {
            end = (pQueryHandle->outputCapacity - numOfRows) + pos - 1;
          }

          start = pos;
        } else {
          int32_t remain = (pos - end) + 1;
          if (remain + numOfRows > pQueryHandle->outputCapacity) {
            end = pos + 1 - (pQueryHandle->outputCapacity - numOfRows);
          }

          start = end;
          end = pos;
        }

        numOfRows = copyDataFromFileBlock(pQueryHandle, pQueryHandle->outputCapacity, numOfRows, start, end);
        pos += (end - start + 1) * step;
      }
    } while (numOfRows < pQueryHandle->outputCapacity);
    
    if (numOfRows < pQueryHandle->outputCapacity) {
      /**
       * if cache is empty, load remain file block data. In contrast, if there are remain data in cache, do NOT
       * copy them all to result buffer, since it may be overlapped with file data block.
       */
      if (node == NULL ||
          ((dataRowKey(SL_GET_NODE_DATA(node)) > pQueryHandle->window.ekey) && ASCENDING_TRAVERSE(pQueryHandle->order)) ||
          ((dataRowKey(SL_GET_NODE_DATA(node)) < pQueryHandle->window.ekey) && !ASCENDING_TRAVERSE(pQueryHandle->order))) {
        // no data in cache or data in cache is greater than the ekey of time window, load data from file block
        if (cur->win.skey == TSKEY_INITIAL_VAL) {
          cur->win.skey = tsArray[pos];
        }

        int32_t start = -1;
        int32_t end = -1;

        // all remain data are qualified, but check the remain capacity in the first place.
        if (ASCENDING_TRAVERSE(pQueryHandle->order)) {
          int32_t remain = endPos - pos + 1;
          if (remain + numOfRows > pQueryHandle->outputCapacity) {
            endPos = (pQueryHandle->outputCapacity - numOfRows) + pos - 1;
          }

          start = pos;
          end = endPos;
        } else {
          int32_t remain = pos + 1;
          if (remain + numOfRows > pQueryHandle->outputCapacity) {
            endPos = pos + 1 - (pQueryHandle->outputCapacity - numOfRows);
          }

          start = endPos;
          end = pos;
        }

        numOfRows = copyDataFromFileBlock(pQueryHandle, pQueryHandle->outputCapacity, numOfRows, start, end);
        pos += (end - start + 1) * step;
      }
    }
  }
  
  cur->blockCompleted = (((pos >= endPos || cur->lastKey > pQueryHandle->window.ekey) && ASCENDING_TRAVERSE(pQueryHandle->order)) ||
      ((pos <= endPos || cur->lastKey < pQueryHandle->window.ekey) && !ASCENDING_TRAVERSE(pQueryHandle->order)));

  if (!ASCENDING_TRAVERSE(pQueryHandle->order)) {
    SWAP(cur->win.skey, cur->win.ekey, TSKEY);
  
    // if the buffer is not full in case of descending order query, move the data in the front of the buffer
    if (numOfRows < pQueryHandle->outputCapacity) {
      int32_t emptySize = pQueryHandle->outputCapacity - numOfRows;
  
      int32_t requiredNumOfCols = taosArrayGetSize(pQueryHandle->pColumns);
      for(int32_t i = 0; i < requiredNumOfCols; ++i) {
        SColumnInfoData* pColInfo = taosArrayGet(pQueryHandle->pColumns, i);
        memmove(pColInfo->pData, pColInfo->pData + emptySize * pColInfo->info.bytes, numOfRows * pColInfo->info.bytes);
      }
    }
  }
  
  pCheckInfo->lastKey = cur->lastKey;
  pQueryHandle->realNumOfRows = numOfRows;
  cur->rows = numOfRows;
  cur->pos = pos;

  tsdbTrace("%p uid:%" PRIu64",tid:%d data block created, brange:%"PRIu64"-%"PRIu64" %p", pQueryHandle, cur->win.skey,
      cur->win.ekey, cur->rows, pQueryHandle->qinfo);
}

int32_t binarySearchForKey(char* pValue, int num, TSKEY key, int order) {
  int    firstPos, lastPos, midPos = -1;
  int    numOfRows;
  TSKEY* keyList;

  if (num <= 0) return -1;

  keyList = (TSKEY*)pValue;
  firstPos = 0;
  lastPos = num - 1;

  if (order == TSDB_ORDER_DESC) {
    // find the first position which is smaller than the key
    while (1) {
      if (key >= keyList[lastPos]) return lastPos;
      if (key == keyList[firstPos]) return firstPos;
      if (key < keyList[firstPos]) return firstPos - 1;

      numOfRows = lastPos - firstPos + 1;
      midPos = (numOfRows >> 1) + firstPos;

      if (key < keyList[midPos]) {
        lastPos = midPos - 1;
      } else if (key > keyList[midPos]) {
        firstPos = midPos + 1;
      } else {
        break;
      }
    }

  } else {
    // find the first position which is bigger than the key
    while (1) {
      if (key <= keyList[firstPos]) return firstPos;
      if (key == keyList[lastPos]) return lastPos;

      if (key > keyList[lastPos]) {
        lastPos = lastPos + 1;
        if (lastPos >= num)
          return -1;
        else
          return lastPos;
      }

      numOfRows = lastPos - firstPos + 1;
      midPos = (numOfRows >> 1) + firstPos;

      if (key < keyList[midPos]) {
        lastPos = midPos - 1;
      } else if (key > keyList[midPos]) {
        firstPos = midPos + 1;
      } else {
        break;
      }
    }
  }

  return midPos;
}

static void cleanBlockOrderSupporter(SBlockOrderSupporter* pSupporter, int32_t numOfTables) {
  tfree(pSupporter->numOfBlocksPerTable);
  tfree(pSupporter->blockIndexArray);

  for (int32_t i = 0; i < numOfTables; ++i) {
    STableBlockInfo* pBlockInfo = pSupporter->pDataBlockInfo[i];
    tfree(pBlockInfo);
  }

  tfree(pSupporter->pDataBlockInfo);
}

static int32_t dataBlockOrderCompar(const void* pLeft, const void* pRight, void* param) {
  int32_t leftTableIndex = *(int32_t*)pLeft;
  int32_t rightTableIndex = *(int32_t*)pRight;

  SBlockOrderSupporter* pSupporter = (SBlockOrderSupporter*)param;

  int32_t leftTableBlockIndex = pSupporter->blockIndexArray[leftTableIndex];
  int32_t rightTableBlockIndex = pSupporter->blockIndexArray[rightTableIndex];

  if (leftTableBlockIndex > pSupporter->numOfBlocksPerTable[leftTableIndex]) {
    /* left block is empty */
    return 1;
  } else if (rightTableBlockIndex > pSupporter->numOfBlocksPerTable[rightTableIndex]) {
    /* right block is empty */
    return -1;
  }

  STableBlockInfo* pLeftBlockInfoEx = &pSupporter->pDataBlockInfo[leftTableIndex][leftTableBlockIndex];
  STableBlockInfo* pRightBlockInfoEx = &pSupporter->pDataBlockInfo[rightTableIndex][rightTableBlockIndex];

  //    assert(pLeftBlockInfoEx->compBlock->offset != pRightBlockInfoEx->compBlock->offset);
  if (pLeftBlockInfoEx->compBlock->offset == pRightBlockInfoEx->compBlock->offset &&
      pLeftBlockInfoEx->compBlock->last == pRightBlockInfoEx->compBlock->last) {
    // todo add more information
    tsdbError("error in header file, two block with same offset:%p", pLeftBlockInfoEx->compBlock->offset);
  }

  return pLeftBlockInfoEx->compBlock->offset > pRightBlockInfoEx->compBlock->offset ? 1 : -1;
}

static int32_t createDataBlocksInfo(STsdbQueryHandle* pQueryHandle, int32_t numOfBlocks, int32_t* numOfAllocBlocks) {
  char* tmp = realloc(pQueryHandle->pDataBlockInfo, sizeof(STableBlockInfo) * numOfBlocks);
  if (tmp == NULL) {
    return TSDB_CODE_TDB_OUT_OF_MEMORY;
  }

  pQueryHandle->pDataBlockInfo = (STableBlockInfo*) tmp;
  memset(pQueryHandle->pDataBlockInfo, 0, sizeof(STableBlockInfo) * numOfBlocks);
  *numOfAllocBlocks = numOfBlocks;

  int32_t numOfTables = taosArrayGetSize(pQueryHandle->pTableCheckInfo);

  SBlockOrderSupporter sup = {0};
  sup.numOfTables = numOfTables;
  sup.numOfBlocksPerTable = calloc(1, sizeof(int32_t) * numOfTables);
  sup.blockIndexArray = calloc(1, sizeof(int32_t) * numOfTables);
  sup.pDataBlockInfo = calloc(1, POINTER_BYTES * numOfTables);

  if (sup.numOfBlocksPerTable == NULL || sup.blockIndexArray == NULL || sup.pDataBlockInfo == NULL) {
    cleanBlockOrderSupporter(&sup, 0);
    return TSDB_CODE_TDB_OUT_OF_MEMORY;
  }
  
  int32_t cnt = 0;
  int32_t numOfQualTables = 0;
  
  for (int32_t j = 0; j < numOfTables; ++j) {
    STableCheckInfo* pTableCheck = (STableCheckInfo*)taosArrayGet(pQueryHandle->pTableCheckInfo, j);
    if (pTableCheck->numOfBlocks <= 0) {
      continue;
    }
    
    SCompBlock* pBlock = pTableCheck->pCompInfo->blocks;
    sup.numOfBlocksPerTable[numOfQualTables] = pTableCheck->numOfBlocks;

    char* buf = calloc(1, sizeof(STableBlockInfo) * pTableCheck->numOfBlocks);
    if (buf == NULL) {
      cleanBlockOrderSupporter(&sup, numOfQualTables);
      return TSDB_CODE_TDB_OUT_OF_MEMORY;
    }

    sup.pDataBlockInfo[numOfQualTables] = (STableBlockInfo*)buf;

    for (int32_t k = 0; k < pTableCheck->numOfBlocks; ++k) {
      STableBlockInfo* pBlockInfo = &sup.pDataBlockInfo[numOfQualTables][k];

      pBlockInfo->compBlock = &pBlock[k];
      pBlockInfo->pTableCheckInfo = pTableCheck;
      //      pBlockInfo->groupIdx = pTableCheckInfo[j]->groupIdx;     // set the group index
      //      pBlockInfo->blockIndex = pTableCheckInfo[j]->start + k;    // set the block index in original table
      cnt++;
    }

    numOfQualTables++;
  }

  tsdbTrace("%p create data blocks info struct completed, %d blocks in %d tables", pQueryHandle, cnt, numOfQualTables);

  assert(cnt <= numOfBlocks && numOfQualTables <= numOfTables);  // the pTableQueryInfo[j]->numOfBlocks may be 0
  sup.numOfTables = numOfQualTables;
  SLoserTreeInfo* pTree = NULL;

  uint8_t ret = tLoserTreeCreate(&pTree, sup.numOfTables, &sup, dataBlockOrderCompar);
  if (ret != TSDB_CODE_SUCCESS) {
    cleanBlockOrderSupporter(&sup, numOfTables);
    return TSDB_CODE_TDB_OUT_OF_MEMORY;
  }

  int32_t numOfTotal = 0;

  while (numOfTotal < cnt) {
    int32_t pos = pTree->pNode[0].index;
    int32_t index = sup.blockIndexArray[pos]++;

    STableBlockInfo* pBlocksInfo = sup.pDataBlockInfo[pos];
    pQueryHandle->pDataBlockInfo[numOfTotal++] = pBlocksInfo[index];

    // set data block index overflow, in order to disable the offset comparator
    if (sup.blockIndexArray[pos] >= sup.numOfBlocksPerTable[pos]) {
      sup.blockIndexArray[pos] = sup.numOfBlocksPerTable[pos] + 1;
    }

    tLoserTreeAdjust(pTree, pos + sup.numOfTables);
  }

  /*
   * available when no import exists
   * for(int32_t i = 0; i < cnt - 1; ++i) {
   *   assert((*pDataBlockInfo)[i].compBlock->offset < (*pDataBlockInfo)[i+1].compBlock->offset);
   * }
   */

  tsdbTrace("%p %d data blocks sort completed", pQueryHandle, cnt);
  cleanBlockOrderSupporter(&sup, numOfTables);
  free(pTree);

  return TSDB_CODE_SUCCESS;
}

// todo opt for only one table case
static bool getDataBlocksInFilesImpl(STsdbQueryHandle* pQueryHandle) {
  pQueryHandle->numOfBlocks = 0;
  SQueryFilePos* cur = &pQueryHandle->cur;
  
  int32_t numOfBlocks = 0;
  int32_t numOfTables = taosArrayGetSize(pQueryHandle->pTableCheckInfo);
  
  while ((pQueryHandle->pFileGroup = tsdbGetFileGroupNext(&pQueryHandle->fileIter)) != NULL) {
    int32_t type = ASCENDING_TRAVERSE(pQueryHandle->order)? QUERY_RANGE_GREATER_EQUAL:QUERY_RANGE_LESS_EQUAL;
    if (getFileCompInfo(pQueryHandle, &numOfBlocks, type) != TSDB_CODE_SUCCESS) {
      break;
    }
    
    tsdbTrace("%p %d blocks found in file for %d table(s), fid:%d", pQueryHandle, numOfBlocks,
           numOfTables, pQueryHandle->pFileGroup->fileId);
    
    assert(numOfBlocks >= 0);
    if (numOfBlocks == 0) {
      continue;
    }
    
    // todo return error code to query engine
    if (createDataBlocksInfo(pQueryHandle, numOfBlocks, &pQueryHandle->numOfBlocks) != TSDB_CODE_SUCCESS) {
      break;
    }
    
    assert(numOfBlocks >= pQueryHandle->numOfBlocks);
    if (pQueryHandle->numOfBlocks > 0) {
      break;
    }
  }
  
  // no data in file anymore
  if (pQueryHandle->numOfBlocks <= 0) {
    assert(pQueryHandle->pFileGroup == NULL);
    cur->fid = -1;  // denote that there are no data in file anymore
    
    return false;
  }
  
  cur->slot = ASCENDING_TRAVERSE(pQueryHandle->order)? 0:pQueryHandle->numOfBlocks-1;
  cur->fid = pQueryHandle->pFileGroup->fileId;
  
  STableBlockInfo* pBlockInfo = &pQueryHandle->pDataBlockInfo[cur->slot];
  return loadFileDataBlock(pQueryHandle, pBlockInfo->compBlock, pBlockInfo->pTableCheckInfo);
}

static bool getDataBlocksInFiles(STsdbQueryHandle* pQueryHandle) {
  STsdbFileH*    pFileHandle = tsdbGetFile(pQueryHandle->pTsdb);
  SQueryFilePos* cur = &pQueryHandle->cur;

  // find the start data block in file
  if (!pQueryHandle->locateStart) {
    pQueryHandle->locateStart = true;
    STsdbCfg* pCfg = &pQueryHandle->pTsdb->config;
    int32_t fid = getFileIdFromKey(pQueryHandle->window.skey, pCfg->daysPerFile, pCfg->precision);
    
    tsdbInitFileGroupIter(pFileHandle, &pQueryHandle->fileIter, pQueryHandle->order);
    tsdbSeekFileGroupIter(&pQueryHandle->fileIter, fid);

    return getDataBlocksInFilesImpl(pQueryHandle);
  } else {
    // check if current file block is all consumed
    STableBlockInfo* pBlockInfo = &pQueryHandle->pDataBlockInfo[cur->slot];
    STableCheckInfo* pCheckInfo = pBlockInfo->pTableCheckInfo;
    
    // current block is done, try next
    if (!cur->mixBlock || cur->blockCompleted) {
      if ((cur->slot == pQueryHandle->numOfBlocks - 1 && ASCENDING_TRAVERSE(pQueryHandle->order)) ||
          (cur->slot == 0 && !ASCENDING_TRAVERSE(pQueryHandle->order))) {
        // all data blocks in current file has been checked already, try next file if exists
        return getDataBlocksInFilesImpl(pQueryHandle);
      } else {
        // next block of the same file
        int32_t step = ASCENDING_TRAVERSE(pQueryHandle->order) ? 1 : -1;
        cur->slot += step;
        
        cur->mixBlock = false;
        cur->blockCompleted = false;
        
        STableBlockInfo* pNext = &pQueryHandle->pDataBlockInfo[cur->slot];
        return loadFileDataBlock(pQueryHandle, pNext->compBlock, pNext->pTableCheckInfo);
      }
    } else {
      handleDataMergeIfNeeded(pQueryHandle, pBlockInfo->compBlock, pCheckInfo);
      return pQueryHandle->realNumOfRows > 0;
    }
  }
}

static bool doHasDataInBuffer(STsdbQueryHandle* pQueryHandle) {
  size_t numOfTables = taosArrayGetSize(pQueryHandle->pTableCheckInfo);
  assert(numOfTables <= ((STsdbRepo*)pQueryHandle->pTsdb)->config.maxTables);
  
  while (pQueryHandle->activeIndex < numOfTables) {
    if (hasMoreDataInCache(pQueryHandle)) {
      return true;
    }
    
    pQueryHandle->activeIndex += 1;
  }
  
  return false;
}

// handle data in cache situation
bool tsdbNextDataBlock(TsdbQueryHandleT* pHandle) {
  STsdbQueryHandle* pQueryHandle = (STsdbQueryHandle*) pHandle;
  
  size_t numOfTables = taosArrayGetSize(pQueryHandle->pTableCheckInfo);
  assert(numOfTables > 0);
  
  if (pQueryHandle->type == TSDB_QUERY_TYPE_EXTERNAL) {
    pQueryHandle->type = TSDB_QUERY_TYPE_ALL;
    pQueryHandle->order = TSDB_ORDER_DESC;
    
    if (!tsdbNextDataBlock(pHandle)) {
      return false;
    }
    
    SArray* sa = getDefaultLoadColumns(pQueryHandle, true);
    /*SDataBlockInfo* pBlockInfo =*/ tsdbRetrieveDataBlockInfo(pHandle);
    /*SArray *pDataBlock = */tsdbRetrieveDataBlock(pHandle, sa);
  
    if (pQueryHandle->cur.win.ekey == pQueryHandle->window.skey) {
      // data already retrieve, discard other data rows and return
      int32_t numOfCols = QH_GET_NUM_OF_COLS(pQueryHandle);
      for (int32_t i = 0; i < numOfCols; ++i) {
        SColumnInfoData* pCol = taosArrayGet(pQueryHandle->pColumns, i);
        memcpy(pCol->pData, pCol->pData + pCol->info.bytes * (pQueryHandle->cur.rows-1), pCol->info.bytes);
      }
  
      pQueryHandle->cur.win  = (STimeWindow){pQueryHandle->window.skey, pQueryHandle->window.skey};
      pQueryHandle->window   = pQueryHandle->cur.win;
      pQueryHandle->cur.rows = 1;
      pQueryHandle->type = TSDB_QUERY_TYPE_EXTERNAL;
      return true;
    } else {
      STsdbQueryHandle* pSecQueryHandle = calloc(1, sizeof(STsdbQueryHandle));
      pSecQueryHandle->order       = TSDB_ORDER_ASC;
      pSecQueryHandle->window      = (STimeWindow) {pQueryHandle->window.skey, INT64_MAX};
      pSecQueryHandle->pTsdb       = pQueryHandle->pTsdb;
      pSecQueryHandle->type        = TSDB_QUERY_TYPE_ALL;
      pSecQueryHandle->cur.fid     = -1;
      pSecQueryHandle->cur.win     = TSWINDOW_INITIALIZER;
      pSecQueryHandle->checkFiles  = true;
      pSecQueryHandle->activeIndex = 0;
      pSecQueryHandle->outputCapacity = ((STsdbRepo*)pSecQueryHandle->pTsdb)->config.maxRowsPerFileBlock;
  
      tsdbInitReadHelper(&pSecQueryHandle->rhelper, (STsdbRepo*) pSecQueryHandle->pTsdb);
  
      // allocate buffer in order to load data blocks from file
      int32_t numOfCols = QH_GET_NUM_OF_COLS(pQueryHandle);
  
      pSecQueryHandle->statis = calloc(numOfCols, sizeof(SDataStatis));
      pSecQueryHandle->pColumns = taosArrayInit(numOfCols, sizeof(SColumnInfoData));
  
      for (int32_t i = 0; i < numOfCols; ++i) {
        SColumnInfoData colInfo = {{0}, 0};
        SColumnInfoData* pCol = taosArrayGet(pQueryHandle->pColumns, i);
        
        colInfo.info = pCol->info;
        colInfo.pData = calloc(1, EXTRA_BYTES + pQueryHandle->outputCapacity * pCol->info.bytes);
        taosArrayPush(pSecQueryHandle->pColumns, &colInfo);
        pSecQueryHandle->statis[i].colId = colInfo.info.colId;
      }
  
      size_t si = taosArrayGetSize(pQueryHandle->pTableCheckInfo);
      pSecQueryHandle->pTableCheckInfo = taosArrayInit(si, sizeof(STableCheckInfo));
      STsdbMeta* pMeta = tsdbGetMeta(pQueryHandle->pTsdb);
      assert(pMeta != NULL);
  
      for (int32_t j = 0; j < si; ++j) {
        STableCheckInfo* pCheckInfo = (STableCheckInfo*) taosArrayGet(pQueryHandle->pTableCheckInfo, j);
    
        STableCheckInfo info = {
            .lastKey = pSecQueryHandle->window.skey,
            .tableId = pCheckInfo->tableId,
            .pTableObj = pCheckInfo->pTableObj,
        };
        
        taosArrayPush(pSecQueryHandle->pTableCheckInfo, &info);
      }
  
      tsdbInitDataBlockLoadInfo(&pSecQueryHandle->dataBlockLoadInfo);
      tsdbInitCompBlockLoadInfo(&pSecQueryHandle->compBlockLoadInfo);
  
      bool ret = tsdbNextDataBlock((void*) pSecQueryHandle);
      assert(ret);

      /*SDataBlockInfo* pBlockInfo =*/ tsdbRetrieveDataBlockInfo((void*) pSecQueryHandle);
      /*SArray *pDataBlock = */tsdbRetrieveDataBlock((void*) pSecQueryHandle, sa);
  
      for (int32_t i = 0; i < numOfCols; ++i) {
        SColumnInfoData* pCol = taosArrayGet(pQueryHandle->pColumns, i);
        memcpy(pCol->pData, pCol->pData + pCol->info.bytes * (pQueryHandle->cur.rows-1), pCol->info.bytes);
  
        SColumnInfoData* pCol1 = taosArrayGet(pSecQueryHandle->pColumns, i);
        assert(pCol->info.colId == pCol1->info.colId);
        
        memcpy(pCol->pData + pCol->info.bytes, pCol1->pData, pCol1->info.bytes);
      }
  
      SColumnInfoData* pTSCol = taosArrayGet(pQueryHandle->pColumns, 0);
      
      pQueryHandle->cur.win  = (STimeWindow){((TSKEY*)pTSCol->pData)[0], ((TSKEY*)pTSCol->pData)[1]};
      pQueryHandle->window   = pQueryHandle->cur.win;
      pQueryHandle->cur.rows = 2;
      
      tsdbCleanupQueryHandle(pSecQueryHandle);
    }
    
    pQueryHandle->type = TSDB_QUERY_TYPE_EXTERNAL;
    return true;
  }
  
  if (pQueryHandle->checkFiles) {
    if (getDataBlocksInFiles(pQueryHandle)) {
      return true;
    }
  
    pQueryHandle->activeIndex = 0;
    pQueryHandle->checkFiles  = false;
  }
  
  // TODO: opt by consider the scan order
  return doHasDataInBuffer(pQueryHandle);
}

void changeQueryHandleForLastrowQuery(TsdbQueryHandleT pqHandle) {
  STsdbQueryHandle* pQueryHandle = (STsdbQueryHandle*) pqHandle;
  assert(!ASCENDING_TRAVERSE(pQueryHandle->order));
  
  // starts from the buffer in case of descending timestamp order check data blocks
  
  // todo consider the query time window, current last_row does not apply the query time window
  size_t numOfTables = taosArrayGetSize(pQueryHandle->pTableCheckInfo);
  
  TSKEY key = TSKEY_INITIAL_VAL;
  int32_t index = -1;
  
  for(int32_t i = 0; i < numOfTables; ++i) {
    STableCheckInfo* pCheckInfo = taosArrayGet(pQueryHandle->pTableCheckInfo, i);
    if (pCheckInfo->pTableObj->tableId.uid == 12094628167747) {
      printf("abc\n");
    }
    if (pCheckInfo->pTableObj->lastKey > key) {
      key = pCheckInfo->pTableObj->lastKey;
      index = i;
    }
  }
  
  if (index == -1) {
    return;
  }
  
  // erase all other elements in array list
  size_t size = taosArrayGetSize(pQueryHandle->pTableCheckInfo);
  for (int32_t i = 0; i < size; ++i) {
    if (i == index) {
      continue;
    }
    
    STableCheckInfo* pTableCheckInfo = taosArrayGet(pQueryHandle->pTableCheckInfo, i);
    tSkipListDestroyIter(pTableCheckInfo->iter);
    
    if (pTableCheckInfo->pDataCols != NULL) {
      tfree(pTableCheckInfo->pDataCols->buf);
    }
    
    tfree(pTableCheckInfo->pDataCols);
    tfree(pTableCheckInfo->pCompInfo);
  }
  
  STableCheckInfo info = *(STableCheckInfo*) taosArrayGet(pQueryHandle->pTableCheckInfo, index);
  taosArrayClear(pQueryHandle->pTableCheckInfo);
  
  info.lastKey = key;
  taosArrayPush(pQueryHandle->pTableCheckInfo, &info);
  
  // update the query time window according to the chosen last timestamp
  pQueryHandle->window = (STimeWindow) {key, key};
}

static void changeQueryHandleForInterpQuery(TsdbQueryHandleT pHandle) {
  // filter the queried time stamp in the first place
  STsdbQueryHandle* pQueryHandle = (STsdbQueryHandle*) pHandle;
  pQueryHandle->order = TSDB_ORDER_DESC;
  
  assert(pQueryHandle->window.skey == pQueryHandle->window.ekey);
  
  // starts from the buffer in case of descending timestamp order check data blocks
  // todo consider the query time window, current last_row does not apply the query time window
  size_t numOfTables = taosArrayGetSize(pQueryHandle->pTableCheckInfo);
  
  int32_t i = 0;
  while(i < numOfTables) {
    STableCheckInfo* pCheckInfo = taosArrayGet(pQueryHandle->pTableCheckInfo, i);
    if (pQueryHandle->window.skey <= pCheckInfo->pTableObj->lastKey &&
        pCheckInfo->pTableObj->lastKey != TSKEY_INITIAL_VAL) {
      break;
    }
    
    i++;
  }
  
  // there are no data in all the tables
  if (i == numOfTables) {
    return;
  }
  
  STableCheckInfo info = *(STableCheckInfo*) taosArrayGet(pQueryHandle->pTableCheckInfo, i);
  taosArrayClear(pQueryHandle->pTableCheckInfo);
  
  info.lastKey = pQueryHandle->window.skey;
  taosArrayPush(pQueryHandle->pTableCheckInfo, &info);
  
  // update the query time window according to the chosen last timestamp
  pQueryHandle->window = (STimeWindow) {info.lastKey, TSKEY_INITIAL_VAL};
}

static int tsdbReadRowsFromCache(SSkipListIterator* pIter, STable* pTable, TSKEY maxKey, int maxRowsToRead, TSKEY* skey, TSKEY* ekey,
                                 STsdbQueryHandle* pQueryHandle) {
  int     numOfRows = 0;
  int32_t numOfCols = taosArrayGetSize(pQueryHandle->pColumns);
  *skey = TSKEY_INITIAL_VAL;

  do {
    SSkipListNode* node = tSkipListIterGet(pIter);
    if (node == NULL) {
      break;
    }

    SDataRow row = SL_GET_NODE_DATA(node);
    TSKEY key = dataRowKey(row);
    
    if ((key > maxKey && ASCENDING_TRAVERSE(pQueryHandle->order)) ||
        (key < maxKey && !ASCENDING_TRAVERSE(pQueryHandle->order))) {
      
      tsdbTrace("%p key:%"PRIu64" beyond qrange:%"PRId64" - %"PRId64", no more data in buffer", pQueryHandle, key, pQueryHandle->window.skey,
          pQueryHandle->window.ekey);
      
      break;
    }

    if (*skey == INT64_MIN) {
      *skey = dataRowKey(row);
    }

    *ekey = dataRowKey(row);

    int32_t offset = -1;
    char* pData = NULL;
  
    STSchema* pSchema = tsdbGetTableSchema(tsdbGetMeta(pQueryHandle->pTsdb), pTable);
    int32_t numOfTableCols = schemaNCols(pSchema);
    
    for (int32_t i = 0; i < numOfCols; ++i) {
      SColumnInfoData* pColInfo = taosArrayGet(pQueryHandle->pColumns, i);
      
      if (ASCENDING_TRAVERSE(pQueryHandle->order)) {
        pData = pColInfo->pData + numOfRows * pColInfo->info.bytes;
      } else {
        pData = pColInfo->pData + (maxRowsToRead - numOfRows - 1) * pColInfo->info.bytes;
      }
      
      for(int32_t j = 0; j < numOfTableCols; ++j) {
        if (pColInfo->info.colId == pSchema->columns[j].colId) {
          offset = pSchema->columns[j].offset;
          break;
        }
      }
      
      assert(offset != -1); // todo handle error
      void *value = tdGetRowDataOfCol(row, pColInfo->info.type, TD_DATA_ROW_HEAD_SIZE + offset);
      
      if (pColInfo->info.type == TSDB_DATA_TYPE_BINARY || pColInfo->info.type == TSDB_DATA_TYPE_NCHAR) {
        memcpy(pData, value, varDataTLen(value));
      } else {
        memcpy(pData, value, pColInfo->info.bytes);
      }
    }

    if (++numOfRows >= maxRowsToRead) {
      tSkipListIterNext(pIter);
      break;
    }
    
  } while(tSkipListIterNext(pIter));

  assert(numOfRows <= maxRowsToRead);
  
  // if the buffer is not full in case of descending order query, move the data in the front of the buffer
  if (!ASCENDING_TRAVERSE(pQueryHandle->order) && numOfRows < maxRowsToRead) {
    int32_t emptySize = maxRowsToRead - numOfRows;
    
    for(int32_t i = 0; i < numOfCols; ++i) {
      SColumnInfoData* pColInfo = taosArrayGet(pQueryHandle->pColumns, i);
      memmove(pColInfo->pData, pColInfo->pData + emptySize * pColInfo->info.bytes, numOfRows * pColInfo->info.bytes);
    }
  }
  
  return numOfRows;
}

SDataBlockInfo tsdbRetrieveDataBlockInfo(TsdbQueryHandleT* pQueryHandle) {
  STsdbQueryHandle* pHandle = (STsdbQueryHandle*)pQueryHandle;
  SQueryFilePos* cur = &pHandle->cur;
  STable* pTable = NULL;
  
  // there are data in file
  if (pHandle->cur.fid >= 0) {
    STableBlockInfo* pBlockInfo = &pHandle->pDataBlockInfo[cur->slot];
    pTable = pBlockInfo->pTableCheckInfo->pTableObj;
  } else {
    STableCheckInfo* pCheckInfo = taosArrayGet(pHandle->pTableCheckInfo, pHandle->activeIndex);
    pTable = pCheckInfo->pTableObj;
  }
  
  SDataBlockInfo blockInfo = {
      .uid = pTable->tableId.uid,
      .tid = pTable->tableId.tid,
      .rows = cur->rows,
      .window = cur->win,
      .numOfCols = QH_GET_NUM_OF_COLS(pHandle),
  };

  return blockInfo;
}

/*
 * return null for mixed data block, if not a complete file data block, the statistics value will always return NULL
 */
int32_t tsdbRetrieveDataBlockStatisInfo(TsdbQueryHandleT* pQueryHandle, SDataStatis** pBlockStatis) {
  STsdbQueryHandle* pHandle = (STsdbQueryHandle*) pQueryHandle;
  
  SQueryFilePos* cur = &pHandle->cur;
  if (cur->mixBlock) {
    *pBlockStatis = NULL;
    return TSDB_CODE_SUCCESS;
  }
  
  assert((cur->slot >= 0 && cur->slot < pHandle->numOfBlocks) ||
      ((cur->slot == pHandle->numOfBlocks) && (cur->slot == 0)));
  
  STableBlockInfo* pBlockInfo = &pHandle->pDataBlockInfo[cur->slot];
  
  // file block with subblocks has no statistics data
  if (pBlockInfo->compBlock->numOfSubBlocks > 1) {
    *pBlockStatis = NULL;
    return TSDB_CODE_SUCCESS;
  }
  
  tsdbLoadCompData(&pHandle->rhelper, pBlockInfo->compBlock, NULL);
  
  size_t numOfCols = QH_GET_NUM_OF_COLS(pHandle);
  for(int32_t i = 0; i < numOfCols; ++i) {
    SDataStatis* st = &pHandle->statis[i];
    int32_t colId = st->colId;
    
    memset(st, 0, sizeof(SDataStatis));
    st->colId = colId;
  }
  
  tsdbGetDataStatis(&pHandle->rhelper, pHandle->statis, numOfCols);
  
  *pBlockStatis = pHandle->statis;
  
  //update the number of NULL data rows
  for(int32_t i = 0; i < numOfCols; ++i) {
    if (pHandle->statis[i].numOfNull == -1) { // set the column data are all NULL
      pHandle->statis[i].numOfNull = pBlockInfo->compBlock->numOfRows;
    }
  }
  
  return TSDB_CODE_SUCCESS;
}

SArray* tsdbRetrieveDataBlock(TsdbQueryHandleT* pQueryHandle, SArray* pIdList) {
  /**
   * In the following two cases, the data has been loaded to SColumnInfoData.
   * 1. data is from cache, 2. data block is not completed qualified to query time range
   */
  STsdbQueryHandle* pHandle = (STsdbQueryHandle*)pQueryHandle;

  if (pHandle->cur.fid < 0) {
    return pHandle->pColumns;
  } else {
    STableBlockInfo* pBlockInfo = &pHandle->pDataBlockInfo[pHandle->cur.slot];
    STableCheckInfo* pCheckInfo = pBlockInfo->pTableCheckInfo;

    if (pHandle->cur.mixBlock) {
      return pHandle->pColumns;
    } else {
      SDataBlockInfo binfo = getTrueDataBlockInfo(pCheckInfo, pBlockInfo->compBlock);
      assert(pHandle->realNumOfRows <= binfo.rows);
  
      // data block has been loaded, todo extract method
      SDataBlockLoadInfo* pBlockLoadInfo = &pHandle->dataBlockLoadInfo;
      
      if (pBlockLoadInfo->slot == pHandle->cur.slot && pBlockLoadInfo->fileGroup->fileId == pHandle->cur.fid &&
          pBlockLoadInfo->tid == pCheckInfo->pTableObj->tableId.tid) {
        return pHandle->pColumns;
      } else {  // only load the file block
        SCompBlock* pBlock = pBlockInfo->compBlock;
        doLoadFileDataBlock(pHandle, pBlock, pCheckInfo);
  
        // todo refactor
        int32_t numOfRows = copyDataFromFileBlock(pHandle, pHandle->outputCapacity, 0, 0, pBlock->numOfRows - 1);
  
        // if the buffer is not full in case of descending order query, move the data in the front of the buffer
        if (!ASCENDING_TRAVERSE(pHandle->order) && numOfRows < pHandle->outputCapacity) {
          int32_t emptySize = pHandle->outputCapacity - numOfRows;
          int32_t reqNumOfCols = taosArrayGetSize(pHandle->pColumns);
    
          for(int32_t i = 0; i < reqNumOfCols; ++i) {
            SColumnInfoData* pColInfo = taosArrayGet(pHandle->pColumns, i);
            memmove(pColInfo->pData, pColInfo->pData + emptySize * pColInfo->info.bytes, numOfRows * pColInfo->info.bytes);
          }
        }
        
        return pHandle->pColumns;
      }
    }
  }
}

SArray* tsdbRetrieveDataRow(TsdbQueryHandleT* pQueryHandle, SArray* pIdList, SQueryRowCond* pCond) { return NULL; }

TsdbQueryHandleT* tsdbQueryFromTagConds(STsdbQueryCond* pCond, int16_t stableId, const char* pTagFilterStr) {
  return NULL;
}

SArray* tsdbGetTableList(TsdbQueryHandleT* pQueryHandle) { return NULL; }

static int32_t getAllTableIdList(STable* pSuperTable, SArray* list) {
  SSkipListIterator* iter = tSkipListCreateIter(pSuperTable->pIndex);
  while (tSkipListIterNext(iter)) {
    SSkipListNode* pNode = tSkipListIterGet(iter);
    
    STableIndexElem* elem = (STableIndexElem*)(SL_GET_NODE_DATA((SSkipListNode*) pNode));
    taosArrayPush(list, &elem->pTable->tableId);
  }
  
  tSkipListDestroyIter(iter);
  return TSDB_CODE_SUCCESS;
}

/**
 * convert the result pointer to table id instead of table object pointer
 * todo remove it by using callback function to change the final result in-time.
 * @param pRes
 */
static void convertQueryResult(SArray* pRes, SArray* pTableList) {
  if (pTableList == NULL || taosArrayGetSize(pTableList) == 0) {
    return;
  }

  size_t size = taosArrayGetSize(pTableList);
  for (int32_t i = 0; i < size; ++i) {  // todo speedup  by using reserve space.
    STableIndexElem* elem = taosArrayGet(pTableList, i);
    taosArrayPush(pRes, &elem->pTable->tableId);
  }
}

static void destroyHelper(void* param) {
  if (param == NULL) {
    return;
  }

  
  tQueryInfo* pInfo = (tQueryInfo*)param;
  if (pInfo->optr != TSDB_RELATION_IN) {
    tfree(pInfo->q);
  }
  
//  tVariantDestroy(&(pInfo->q));
  free(param);
}

static int32_t getTagColumnIndex(STSchema* pTSchema, SSchema* pSchema) {
  // filter on table name(TBNAME)
  if (strcasecmp(pSchema->name, TSQL_TBNAME_L) == 0) {
    return TSDB_TBNAME_COLUMN_INDEX;
  }
  
  for(int32_t i = 0; i < schemaNCols(pTSchema); ++i) {
    STColumn* pColumn = &pTSchema->columns[i];
    if (pColumn->bytes == pSchema->bytes && pColumn->type  == pSchema->type  && pColumn->colId == pSchema->colId) {
      return i;
    }
  }
  
  return -2;
}

void filterPrepare(void* expr, void* param) {
  tExprNode* pExpr = (tExprNode*)expr;
  if (pExpr->_node.info != NULL) {
    return;
  }

  int32_t i = 0;
  pExpr->_node.info = calloc(1, sizeof(tQueryInfo));
  
  STSchema* pTSSchema = (STSchema*) param;

  tQueryInfo* pInfo = pExpr->_node.info;
  tVariant*   pCond = pExpr->_node.pRight->pVal;
  SSchema*    pSchema = pExpr->_node.pLeft->pSchema;

  // todo : if current super table does not change schema yet, this function may fail to get correct schema, test case
  int32_t index = getTagColumnIndex(pTSSchema, pSchema);
  assert((index >= 0 && i < TSDB_MAX_TAGS) || (index == TSDB_TBNAME_COLUMN_INDEX));

  pInfo->sch      = *pSchema;
  pInfo->colIndex = index;
  pInfo->optr     = pExpr->_node.optr;
  pInfo->compare  = getComparFunc(pSchema->type, pInfo->optr);
  pInfo->param    = pTSSchema;
  
  if (pInfo->optr == TSDB_RELATION_IN) {
    pInfo->q = (char*) pCond->arr;
  } else {
    pInfo->q = calloc(1, pSchema->bytes);
    tVariantDump(pCond, pInfo->q, pSchema->type, true);
  }
}

typedef struct STableGroupSupporter {
  int32_t    numOfCols;
  SColIndex* pCols;
  STSchema*  pTagSchema;
  void*      tsdbMeta;
} STableGroupSupporter;

int32_t tableGroupComparFn(const void *p1, const void *p2, const void *param) {
  STableGroupSupporter* pTableGroupSupp = (STableGroupSupporter*) param;
  STableId* id1 = (STableId*) p1;
  STableId* id2 = (STableId*) p2;
  
  STable *pTable1 = tsdbGetTableByUid(pTableGroupSupp->tsdbMeta, id1->uid);
  STable *pTable2 = tsdbGetTableByUid(pTableGroupSupp->tsdbMeta, id2->uid);
  
  for (int32_t i = 0; i < pTableGroupSupp->numOfCols; ++i) {
    SColIndex* pColIndex = &pTableGroupSupp->pCols[i];
    int32_t colIndex = pColIndex->colIndex;
    
    assert((colIndex >= 0 && colIndex < schemaNCols(pTableGroupSupp->pTagSchema)) ||
           (colIndex == TSDB_TBNAME_COLUMN_INDEX));
    
    char *  f1 = NULL;
    char *  f2 = NULL;
    int32_t type = 0;
    int32_t bytes = 0;
    
    if (colIndex == TSDB_TBNAME_COLUMN_INDEX) {  // todo refactor extract method , to queryExecutor to generate tags values
      f1 = (char*) pTable1->name;
      f2 = (char*) pTable2->name;
      type = TSDB_DATA_TYPE_BINARY;
      bytes = TSDB_TABLE_NAME_LEN + VARSTR_HEADER_SIZE;
    } else {
      STColumn* pCol = schemaColAt(pTableGroupSupp->pTagSchema, colIndex);
      bytes = pCol->bytes;
      type = pCol->type;
      f1 = tdGetKVRowValOfCol(pTable1->tagVal, pCol->colId);
      f2 = tdGetKVRowValOfCol(pTable2->tagVal, pCol->colId);
    }
    
    int32_t ret = doCompare(f1, f2, type, bytes);
    if (ret == 0) {
      continue;
    } else {
      return ret;
    }
  }
  
  return 0;
}

void createTableGroupImpl(SArray* pGroups, SArray* pTableIdList, size_t numOfTables, STableGroupSupporter* pSupp,
    __ext_compar_fn_t compareFn) {
  STableId* pId = taosArrayGet(pTableIdList, 0);
  
  SArray* g = taosArrayInit(16, sizeof(STableId));
  taosArrayPush(g, pId);
  
  for (int32_t i = 1; i < numOfTables; ++i) {
    STableId* prev = taosArrayGet(pTableIdList, i - 1);
    STableId* p = taosArrayGet(pTableIdList, i);
    
    int32_t ret = compareFn(prev, p, pSupp);
    assert(ret == 0 || ret == -1);
    
    if (ret == 0) {
      taosArrayPush(g, p);
    } else {
      taosArrayPush(pGroups, &g);  // current group is ended, start a new group
      g = taosArrayInit(16, sizeof(STableId));
      
      taosArrayPush(g, p);
    }
  }
  
  taosArrayPush(pGroups, &g);
}

SArray* createTableGroup(SArray* pTableList, STSchema* pTagSchema, SColIndex* pCols, int32_t numOfOrderCols,
    TsdbRepoT* tsdb) {
  assert(pTableList != NULL);
  SArray* pTableGroup = taosArrayInit(1, POINTER_BYTES);
  
  size_t size = taosArrayGetSize(pTableList);
  if (size == 0) {
    tsdbTrace("no qualified tables");
    return pTableGroup;
  }
  
  if (numOfOrderCols == 0 || size == 1) { // no group by tags clause or only one table
    SArray* sa = taosArrayInit(size, sizeof(STableId));
    for(int32_t i = 0; i < size; ++i) {
      STableId* tableId = taosArrayGet(pTableList, i);
      taosArrayPush(sa, tableId);
    }
    
    taosArrayPush(pTableGroup, &sa);
    tsdbTrace("all %d tables belong to one group", size);
  } else {
    STableGroupSupporter *pSupp = (STableGroupSupporter *) calloc(1, sizeof(STableGroupSupporter));
    pSupp->tsdbMeta = tsdbGetMeta(tsdb);
    pSupp->numOfCols = numOfOrderCols;
    pSupp->pTagSchema = pTagSchema;
    pSupp->pCols = pCols;
    
    taosqsort(pTableList->pData, size, sizeof(STableId), pSupp, tableGroupComparFn);
    createTableGroupImpl(pTableGroup, pTableList, size, pSupp, tableGroupComparFn);
    tfree(pSupp);
  }
  
  return pTableGroup;
}

bool indexedNodeFilterFp(const void* pNode, void* param) {
  tQueryInfo* pInfo = (tQueryInfo*) param;
  
  STableIndexElem* elem = (STableIndexElem*)(SL_GET_NODE_DATA((SSkipListNode*)pNode));

  char*  val = NULL;
  int8_t type = pInfo->sch.type;

  if (pInfo->colIndex == TSDB_TBNAME_COLUMN_INDEX) {
    val = (char*) elem->pTable->name;
    type = TSDB_DATA_TYPE_BINARY;
  } else {
    val = tdGetKVRowValOfCol(elem->pTable->tagVal, pInfo->sch.colId);
  }
  
  //todo :the val is possible to be null, so check it out carefully
  int32_t ret = 0;
  if (type == TSDB_DATA_TYPE_BINARY || type == TSDB_DATA_TYPE_NCHAR) {
    if (pInfo->optr == TSDB_RELATION_IN) {
      ret = pInfo->compare(val, pInfo->q);
    } else {
      ret = pInfo->compare(val, pInfo->q);
    }
  } else {
    ret = pInfo->compare(val, pInfo->q);
  }

  switch (pInfo->optr) {
    case TSDB_RELATION_EQUAL: {
      return ret == 0;
    }
    case TSDB_RELATION_NOT_EQUAL: {
      return ret != 0;
    }
    case TSDB_RELATION_GREATER_EQUAL: {
      return ret >= 0;
    }
    case TSDB_RELATION_GREATER: {
      return ret > 0;
    }
    case TSDB_RELATION_LESS_EQUAL: {
      return ret <= 0;
    }
    case TSDB_RELATION_LESS: {
      return ret < 0;
    }
    case TSDB_RELATION_LIKE: {
      return ret == 0;
    }
    case TSDB_RELATION_IN: {
      return ret == 1;
    }

    default:
      assert(false);
  }
  
  return true;
}

static int32_t doQueryTableList(STable* pSTable, SArray* pRes, tExprNode* pExpr) {
  // query according to the expression tree
  SExprTraverseSupp supp = {
      .nodeFilterFn = (__result_filter_fn_t) indexedNodeFilterFp,
      .setupInfoFn = filterPrepare,
      .pExtInfo = pSTable->tagSchema,
      };

  SArray* pTableList = taosArrayInit(8, sizeof(STableIndexElem));

  tExprTreeTraverse(pExpr, pSTable->pIndex, pTableList, &supp);
  tExprTreeDestroy(&pExpr, destroyHelper);

  convertQueryResult(pRes, pTableList);
  taosArrayDestroy(pTableList);
  return TSDB_CODE_SUCCESS;
}

int32_t tsdbQuerySTableByTagCond(TsdbRepoT* tsdb, uint64_t uid, const char* pTagCond, size_t len,
                                 int16_t tagNameRelType, const char* tbnameCond, STableGroupInfo* pGroupInfo,
                                 SColIndex* pColIndex, int32_t numOfCols) {
  STable* pTable = tsdbGetTableByUid(tsdbGetMeta(tsdb), uid);
  if (pTable == NULL) {
    tsdbError("%p failed to get stable, uid:%" PRIu64, tsdb, uid);
    return TSDB_CODE_TDB_INVALID_TABLE_ID;
  }
  
  if (pTable->type != TSDB_SUPER_TABLE) {
    tsdbError("%p query normal tag not allowed, uid:%" PRIu64 ", tid:%d, name:%s",
           tsdb, uid, pTable->tableId.tid, pTable->name);
    
    return TSDB_CODE_COM_OPS_NOT_SUPPORT; //basically, this error is caused by invalid sql issued by client
  }
  
  SArray* res = taosArrayInit(8, sizeof(STableId));
  STSchema* pTagSchema = tsdbGetTableTagSchema(tsdbGetMeta(tsdb), pTable);
  
  // no tags and tbname condition, all child tables of this stable are involved
  if (tbnameCond == NULL && (pTagCond == NULL || len == 0)) {
    int32_t ret = getAllTableIdList(pTable, res);
    if (ret == TSDB_CODE_SUCCESS) {
      pGroupInfo->numOfTables = taosArrayGetSize(res);
      pGroupInfo->pGroupList  = createTableGroup(res, pTagSchema, pColIndex, numOfCols, tsdb);
      
      tsdbTrace("no tbname condition or tagcond, all tables belongs to one group, numOfTables:%d", pGroupInfo->numOfTables);
    } else {
      // todo add error
    }
    
    taosArrayDestroy(res);
    return ret;
  }

  int32_t ret = TSDB_CODE_SUCCESS;
  tExprNode* expr = NULL;

  TRY(32) {
    expr = exprTreeFromTableName(tbnameCond);
    if (expr == NULL) {
      expr = exprTreeFromBinary(pTagCond, len);
    } else {
      CLEANUP_PUSH_VOID_PTR_PTR(true, tExprNodeDestroy, expr, NULL);
      tExprNode* tagExpr = exprTreeFromBinary(pTagCond, len);
      if (tagExpr != NULL) {
        CLEANUP_PUSH_VOID_PTR_PTR(true, tExprNodeDestroy, tagExpr, NULL);
        tExprNode* tbnameExpr = expr;
        expr = calloc(1, sizeof(tExprNode));
        if (expr == NULL) {
          THROW( TSDB_CODE_TDB_OUT_OF_MEMORY );
        }
        expr->nodeType = TSQL_NODE_EXPR;
        expr->_node.optr = tagNameRelType;
        expr->_node.pLeft = tagExpr;
        expr->_node.pRight = tbnameExpr;
      }
    }
    CLEANUP_EXECUTE();

  } CATCH( code ) {
    CLEANUP_EXECUTE();
    ret = code;
    // TODO: more error handling
  } END_TRY

  doQueryTableList(pTable, res, expr);
  pGroupInfo->numOfTables = taosArrayGetSize(res);
  pGroupInfo->pGroupList  = createTableGroup(res, pTagSchema, pColIndex, numOfCols, tsdb);

  taosArrayDestroy(res);
  return ret;
}

int32_t tsdbGetOneTableGroup(TsdbRepoT* tsdb, uint64_t uid, STableGroupInfo* pGroupInfo) {
  STable* pTable = tsdbGetTableByUid(tsdbGetMeta(tsdb), uid);
  if (pTable == NULL) {
    return TSDB_CODE_TDB_INVALID_TABLE_ID;
  }
  
  //todo assert table type, add the table ref count
  pGroupInfo->numOfTables = 1;
  pGroupInfo->pGroupList = taosArrayInit(1, POINTER_BYTES);
  
  SArray* group = taosArrayInit(1, sizeof(STableId));
  
  taosArrayPush(group, &pTable->tableId);
  taosArrayPush(pGroupInfo->pGroupList, &group);
  
  return TSDB_CODE_SUCCESS;
}

void tsdbCleanupQueryHandle(TsdbQueryHandleT queryHandle) {
  STsdbQueryHandle* pQueryHandle = (STsdbQueryHandle*)queryHandle;
  if (pQueryHandle == NULL) {
    return;
  }
  
  size_t size = taosArrayGetSize(pQueryHandle->pTableCheckInfo);
  for (int32_t i = 0; i < size; ++i) {
    STableCheckInfo* pTableCheckInfo = taosArrayGet(pQueryHandle->pTableCheckInfo, i);
    tSkipListDestroyIter(pTableCheckInfo->iter);

    if (pTableCheckInfo->pDataCols != NULL) {
      tfree(pTableCheckInfo->pDataCols->buf);
    }

    tfree(pTableCheckInfo->pDataCols);
    tfree(pTableCheckInfo->pCompInfo);
  }

  taosArrayDestroy(pQueryHandle->pTableCheckInfo);

   size_t cols = taosArrayGetSize(pQueryHandle->pColumns);
   for (int32_t i = 0; i < cols; ++i) {
     SColumnInfoData* pColInfo = taosArrayGet(pQueryHandle->pColumns, i);
     tfree(pColInfo->pData);
   }

  taosArrayDestroy(pQueryHandle->pColumns);
  tfree(pQueryHandle->pDataBlockInfo);
  tfree(pQueryHandle->statis);
  
  tsdbDestroyHelper(&pQueryHandle->rhelper);
  
  tfree(pQueryHandle);
}