diff --git a/src/client/inc/tsclient.h b/src/client/inc/tsclient.h
index 3625900cd265db29eddc1ed8a8d27fad859415f3..cdcea63c88082174438c747023402fd965ca13da 100644
--- a/src/client/inc/tsclient.h
+++ b/src/client/inc/tsclient.h
@@ -30,10 +30,10 @@ extern "C" {
 #include "tsqlfunction.h"
 #include "tutil.h"
 
+#include "qExecutor.h"
 #include "qsqlparser.h"
 #include "qsqltype.h"
 #include "qtsbuf.h"
-#include "queryExecutor.h"
 
 // forward declaration
 struct SSqlInfo;
diff --git a/src/inc/taosdef.h b/src/inc/taosdef.h
index 23436fe6a589a805a165da4d1260b5c97dc3fa84..ec9655a66e49648a509bcd0b6ebdf561d971b37e 100644
--- a/src/inc/taosdef.h
+++ b/src/inc/taosdef.h
@@ -32,7 +32,7 @@ extern "C" {
 #define TSKEY int64_t
 #endif
 
-#define TSWINDOW_INITIALIZER {INT64_MIN, INT64_MAX};
+#define TSWINDOW_INITIALIZER ((STimeWindow) {INT64_MIN, INT64_MAX})
 #define TSKEY_INITIAL_VAL    INT64_MIN
 
 // ----------------- For variable data types such as TSDB_DATA_TYPE_BINARY and TSDB_DATA_TYPE_NCHAR
diff --git a/src/inc/tsdb.h b/src/inc/tsdb.h
index 32e35416927d144cdf3dabaa51e29ada6d390ac9..b1877838ca2b291b1109e85d5860c0de7a44b0f9 100644
--- a/src/inc/tsdb.h
+++ b/src/inc/tsdb.h
@@ -167,12 +167,6 @@ typedef struct {
   SArray *pGroupList;
 } STableGroupInfo;
 
-typedef struct {
-} SFields;
-
-#define TSDB_TS_GREATER_EQUAL 1
-#define TSDB_TS_LESS_EQUAL 2
-
 typedef struct SQueryRowCond {
   int32_t rel;
   TSKEY   ts;
diff --git a/src/query/inc/queryExecutor.h b/src/query/inc/qExecutor.h
similarity index 100%
rename from src/query/inc/queryExecutor.h
rename to src/query/inc/qExecutor.h
diff --git a/src/query/inc/queryUtil.h b/src/query/inc/qUtil.h
similarity index 100%
rename from src/query/inc/queryUtil.h
rename to src/query/inc/qUtil.h
diff --git a/src/query/inc/tlosertree.h b/src/query/inc/tlosertree.h
index 197d27a76126097f23cfc47a227957301f5b2c5c..4c731625dd5c7950c321b2180ca913e49362059b 100644
--- a/src/query/inc/tlosertree.h
+++ b/src/query/inc/tlosertree.h
@@ -32,7 +32,7 @@ typedef struct SLoserTreeNode {
 typedef struct SLoserTreeInfo {
   int32_t              numOfEntries;
   int32_t              totalEntries;
-  __merge_compare_fn_t comparaFn;
+  __merge_compare_fn_t comparFn;
   void *               param;
 
   SLoserTreeNode *pNode;
diff --git a/src/query/src/queryExecutor.c b/src/query/src/qExecutor.c
similarity index 99%
rename from src/query/src/queryExecutor.c
rename to src/query/src/qExecutor.c
index 913cd4280c4661e8c658ea60d9d5409c0ca7ebf5..81b179fbe636fb11f0b19f3e26d1b55888d4b0c1 100644
--- a/src/query/src/queryExecutor.c
+++ b/src/query/src/qExecutor.c
@@ -17,18 +17,18 @@
 
 #include "hash.h"
 #include "hashfunc.h"
+#include "qExecutor.h"
+#include "qUtil.h"
 #include "qast.h"
 #include "qresultBuf.h"
 #include "query.h"
-#include "queryExecutor.h"
 #include "queryLog.h"
-#include "queryUtil.h"
 #include "taosmsg.h"
+#include "tdataformat.h"
 #include "tlosertree.h"
+#include "tscUtil.h"  // todo move the function to common module
 #include "tscompression.h"
 #include "ttime.h"
-#include "tscUtil.h"   // todo move the function to common module
-#include "tdataformat.h"
 
 #define DEFAULT_INTERN_BUF_SIZE 16384L
 
diff --git a/src/query/src/queryFilterFunc.c b/src/query/src/qFilterFunc.c
similarity index 99%
rename from src/query/src/queryFilterFunc.c
rename to src/query/src/qFilterFunc.c
index 41a888e92d6134f004afce614719e07376b8a198..bcc9531c4e888e8a5bf70a363cb4b148df0aac53 100644
--- a/src/query/src/queryFilterFunc.c
+++ b/src/query/src/qFilterFunc.c
@@ -16,10 +16,10 @@
 #define _DEFAULT_SOURCE
 #include "os.h"
 
+#include "qExecutor.h"
 #include "taosmsg.h"
-#include "tsqlfunction.h"
-#include "queryExecutor.h"
 #include "tcompare.h"
+#include "tsqlfunction.h"
 
 bool less_i8(SColumnFilterElem *pFilter, char *minval, char *maxval) {
   return (*(int8_t *)minval < pFilter->filterInfo.upperBndi);
diff --git a/src/query/src/queryUtil.c b/src/query/src/qUtil.c
similarity index 99%
rename from src/query/src/queryUtil.c
rename to src/query/src/qUtil.c
index 9da02f9f0f9d97c5087027309bde844c09589ecd..87ad9dbeb4601e08c92de4ba98f296c3eb30c0db 100644
--- a/src/query/src/queryUtil.c
+++ b/src/query/src/qUtil.c
@@ -23,8 +23,8 @@
 #include "qinterpolation.h"
 #include "ttime.h"
 
-#include "queryExecutor.h"
-#include "queryUtil.h"
+#include "qExecutor.h"
+#include "qUtil.h"
 
 int32_t initWindowResInfo(SWindowResInfo *pWindowResInfo, SQueryRuntimeEnv *pRuntimeEnv, int32_t size,
                           int32_t threshold, int16_t type) {
diff --git a/src/query/src/qast.c b/src/query/src/qast.c
index f727acb72096e66bba6f377be20bcc3b46187df0..d784fa4102194558c7e3149d07491c2c6e319d4f 100644
--- a/src/query/src/qast.c
+++ b/src/query/src/qast.c
@@ -476,44 +476,6 @@ typedef struct {
   SEndPoint* end;
 } SQueryCond;
 
-//static void setInitialValueForRangeQueryCondition(tSKipListQueryCond *q, int8_t type) {
-//  q->lowerBndRelOptr = TSDB_RELATION_GREATER;
-//  q->upperBndRelOptr = TSDB_RELATION_LESS;
-//
-//  switch (type) {
-//    case TSDB_DATA_TYPE_BOOL:
-//    case TSDB_DATA_TYPE_TINYINT:
-//    case TSDB_DATA_TYPE_SMALLINT:
-//    case TSDB_DATA_TYPE_INT:
-//    case TSDB_DATA_TYPE_BIGINT: {
-//      q->upperBnd.nType = TSDB_DATA_TYPE_BIGINT;
-//      q->lowerBnd.nType = TSDB_DATA_TYPE_BIGINT;
-//
-//      q->upperBnd.i64Key = INT64_MAX;
-//      q->lowerBnd.i64Key = INT64_MIN;
-//      break;
-//    };
-//    case TSDB_DATA_TYPE_FLOAT:
-//    case TSDB_DATA_TYPE_DOUBLE: {
-//      q->upperBnd.nType = TSDB_DATA_TYPE_DOUBLE;
-//      q->lowerBnd.nType = TSDB_DATA_TYPE_DOUBLE;
-//      q->upperBnd.dKey = DBL_MAX;
-//      q->lowerBnd.dKey = -DBL_MIN;
-//      break;
-//    };
-//    case TSDB_DATA_TYPE_NCHAR:
-//    case TSDB_DATA_TYPE_BINARY: {
-//      q->upperBnd.nType = type;
-//      q->upperBnd.pz = NULL;
-//      q->upperBnd.nLen = -1;
-//
-//      q->lowerBnd.nType = type;
-//      q->lowerBnd.pz = NULL;
-//      q->lowerBnd.nLen = -1;
-//    }
-//  }
-//}
-
 // todo check for malloc failure
 static int32_t setQueryCond(tQueryInfo *queryColInfo, SQueryCond* pCond) {
   int32_t optr = queryColInfo->optr;
@@ -788,7 +750,6 @@ static void exprTreeTraverseImpl(tExprNode *pExpr, SArray *pResult, SExprTravers
   taosArrayCopy(pResult, array);
 }
 
-
 static void tSQLBinaryTraverseOnSkipList(tExprNode *pExpr, SArray *pResult, SSkipList *pSkipList, SExprTraverseSupp *param ) {
   SSkipListIterator* iter = tSkipListCreateIter(pSkipList);
 
@@ -834,8 +795,6 @@ static void tQueryIndexlessColumn(SSkipList* pSkipList, tQueryInfo* pQueryInfo,
   tSkipListDestroyIter(iter);
 }
 
-
-
 // post-root order traverse syntax tree
 void tExprTreeTraverse(tExprNode *pExpr, SSkipList *pSkipList, SArray *result, SExprTraverseSupp *param) {
   if (pExpr == NULL) {
@@ -1100,7 +1059,6 @@ static char* exception_strdup(const char* str) {
   return p;
 }
 
-
 static tExprNode* exprTreeFromBinaryImpl(SBufferReader* br) {
   int32_t anchor = CLEANUP_GET_ANCHOR();
 
diff --git a/src/query/src/qinterpolation.c b/src/query/src/qinterpolation.c
index c1939badcc697056f39fe8490967607006db4db6..6573f38682062bef41e9d25ecc89b4874a6f16a8 100644
--- a/src/query/src/qinterpolation.c
+++ b/src/query/src/qinterpolation.c
@@ -185,6 +185,7 @@ int32_t taosNumOfRemainRows(SFillInfo* pFillInfo) {
                                                 : pFillInfo->rowIdx + 1;
 }
 
+// todo: refactor
 static double linearInterpolationImpl(double v1, double v2, double k1, double k2, double k) {
   return v1 + (v2 - v1) * (k - k1) / (k2 - k1);
 }
@@ -449,14 +450,6 @@ int32_t taosDoInterpoResult(SFillInfo* pFillInfo, tFilePage** data, int32_t numO
   }
 }
 
-void taosFillInfoSetSource(SFillInfo* pFillInfo, tFilePage **data, TSKEY endKey) {
-  pFillInfo->endKey = endKey;
-  
-  for (int32_t i = 0; i < pFillInfo->numOfCols; ++i) {
-    memcpy(pFillInfo->pData[i], data[i]->data, pFillInfo->numOfRows * pFillInfo->pFillCol[i].col.bytes);
-  }
-}
-
 void taosGenerateDataBlock(SFillInfo* pFillInfo, tFilePage** output, int64_t* outputRows, int32_t capacity) {
     int32_t remain = taosNumOfRemainRows(pFillInfo);  // todo use iterator?
     
diff --git a/src/query/src/tlosertree.c b/src/query/src/tlosertree.c
index 4e3063da03c675999c4f00cae4163b3d163baf37..0d81f4604bfde20548a8eedf0e323a5a7125adf0 100644
--- a/src/query/src/tlosertree.c
+++ b/src/query/src/tlosertree.c
@@ -54,7 +54,7 @@ uint32_t tLoserTreeCreate(SLoserTreeInfo** pTree, int32_t numOfEntries, void* pa
   (*pTree)->numOfEntries = numOfEntries;
   (*pTree)->totalEntries = totalEntries;
   (*pTree)->param = param;
-  (*pTree)->comparaFn = compareFn;
+  (*pTree)->comparFn = compareFn;
 
   // set initial value for loser tree
   tLoserTreeInit(*pTree);
@@ -95,7 +95,7 @@ void tLoserTreeAdjust(SLoserTreeInfo* pTree, int32_t idx) {
       return;
     }
 
-    int32_t ret = pTree->comparaFn(&pTree->pNode[parentId], &kLeaf, pTree->param);
+    int32_t ret = pTree->comparFn(&pTree->pNode[parentId], &kLeaf, pTree->param);
     if (ret < 0) {
       SLoserTreeNode t = pTree->pNode[parentId];
       pTree->pNode[parentId] = kLeaf;
diff --git a/src/tsdb/src/tsdbRead.c b/src/tsdb/src/tsdbRead.c
index a5cba70219a542963cc92b7e276866a8f1461c53..c84b55f11081fda7ea97bb6e8a06cd84ad50b2ab 100644
--- a/src/tsdb/src/tsdbRead.c
+++ b/src/tsdb/src/tsdbRead.c
@@ -49,6 +49,9 @@ typedef struct SQueryFilePos {
   int32_t slot;
   int32_t pos;
   int64_t lastKey;
+  int32_t rows;
+  bool    mixBlock;
+  STimeWindow win;
 } SQueryFilePos;
 
 typedef struct SDataBlockLoadInfo {
@@ -61,7 +64,6 @@ typedef struct SDataBlockLoadInfo {
 typedef struct SLoadCompBlockInfo {
   int32_t tid; /* table tid */
   int32_t fileId;
-  int32_t fileListIndex;
 } SLoadCompBlockInfo;
 
 typedef struct STableCheckInfo {
@@ -71,10 +73,13 @@ typedef struct STableCheckInfo {
   int32_t    start;
   SCompInfo* pCompInfo;
   int32_t    compSize;
-  int32_t    numOfBlocks;  // number of qualified data blocks not the original blocks
+  int32_t    numOfBlocks;    // number of qualified data blocks not the original blocks
   SDataCols* pDataCols;
   
-  SSkipListIterator* iter;
+  SSkipListIterator* iter;   // skip list iterator
+  SSkipListIterator* iiter;  // imem iterator
+  
+  bool       hasObtainBuf;   // if we should initialize the in-memory skip list iterator
 } STableCheckInfo;
 
 typedef struct {
@@ -110,6 +115,7 @@ typedef struct STsdbQueryHandle {
   SField**    pFields;
   SArray*     pColumns;    // column list, SColumnInfoData array list
   bool        locateStart;
+  int32_t     outputCapacity;
   int32_t     realNumOfRows;
   SArray*     pTableCheckInfo;  //SArray<STableCheckInfo>
   int32_t     activeIndex;
@@ -134,7 +140,6 @@ static void tsdbInitDataBlockLoadInfo(SDataBlockLoadInfo* pBlockLoadInfo) {
 static void tsdbInitCompBlockLoadInfo(SLoadCompBlockInfo* pCompBlockLoadInfo) {
   pCompBlockLoadInfo->tid = -1;
   pCompBlockLoadInfo->fileId = -1;
-  pCompBlockLoadInfo->fileListIndex = -1;
 }
 
 TsdbQueryHandleT* tsdbQueryTables(TsdbRepoT* tsdb, STsdbQueryCond* pCond, STableGroupInfo* groupList) {
@@ -149,6 +154,7 @@ TsdbQueryHandleT* tsdbQueryTables(TsdbRepoT* tsdb, STsdbQueryCond* pCond, STable
   tsdbInitReadHelper(&pQueryHandle->rhelper, (STsdbRepo*) tsdb);
 
   pQueryHandle->cur.fid = -1;
+  pQueryHandle->cur.win = TSWINDOW_INITIALIZER;
 
   size_t sizeOfGroup = taosArrayGetSize(groupList->pGroupList);
   assert(sizeOfGroup >= 1 && pCond != NULL && pCond->numOfCols > 0);
@@ -186,15 +192,15 @@ TsdbQueryHandleT* tsdbQueryTables(TsdbRepoT* tsdb, STsdbQueryCond* pCond, STable
 
   // allocate buffer in order to load data blocks from file
   int32_t numOfCols = pCond->numOfCols;
-  size_t  bufferCapacity = 4096;
-
+  pQueryHandle->outputCapacity = 4096;
+  
   pQueryHandle->pColumns = taosArrayInit(numOfCols, sizeof(SColumnInfoData));
   for (int32_t i = 0; i < pCond->numOfCols; ++i) {
-    SColumnInfoData  pDest = {{0}, 0};
-
-    pDest.info = pCond->colList[i];
-    pDest.pData = calloc(1, EXTRA_BYTES + bufferCapacity * pCond->colList[i].bytes);
-    taosArrayPush(pQueryHandle->pColumns, &pDest);
+    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);
   }
 
   tsdbInitDataBlockLoadInfo(&pQueryHandle->dataBlockLoadInfo);
@@ -223,6 +229,72 @@ TsdbQueryHandleT tsdbQueryRowsInExternalWindow(TsdbRepoT *tsdb, STsdbQueryCond*
   return pQueryHandle;
 }
 
+static bool initSkipListIterator(STsdbQueryHandle* pHandle, STableCheckInfo* pCheckInfo) {
+  STable* pTable = pCheckInfo->pTableObj;
+  assert(pTable != NULL);
+  
+  if (pCheckInfo->hasObtainBuf) {
+    return true;
+  }
+  
+  pCheckInfo->hasObtainBuf = 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
+    uTrace("%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 {
+    uTrace("%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
+    uTrace("%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 {
+    uTrace("%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);
@@ -270,9 +342,8 @@ static bool hasMoreDataInCache(STsdbQueryHandle* pHandle) {
   return true;
 }
 
-// todo dynamic get the daysperfile
-static int32_t getFileIdFromKey(TSKEY key) {
-  int64_t fid = (int64_t)(key / (10 * tsMsPerDay[0]));  // set the starting fileId
+static int32_t getFileIdFromKey(TSKEY key, int32_t daysPerFile) {
+  int64_t fid = (int64_t)(key / (daysPerFile * tsMsPerDay[0]));  // set the starting fileId
   if (fid > INT32_MAX) {
     fid = INT32_MAX;
   }
@@ -409,7 +480,7 @@ static SArray* getDefaultLoadColumns(STsdbQueryHandle* pQueryHandle, bool loadTS
   return pLocalIdList;
 }
 
-static void    filterDataInDataBlock(STsdbQueryHandle* pQueryHandle, STableCheckInfo* pCheckInfo, SCompBlock* pBlock,
+static void    mergeDataInDataBlock(STsdbQueryHandle* pQueryHandle, STableCheckInfo* pCheckInfo, SCompBlock* pBlock,
                                      SArray* sa);
 static int32_t binarySearchForKey(char* pValue, int num, TSKEY key, int order);
 
@@ -456,17 +527,17 @@ static bool loadFileDataBlock(STsdbQueryHandle* pQueryHandle, SCompBlock* pBlock
         return false;
       }
   
-      SDataCols* pCols = pQueryHandle->rhelper.pDataCols[0];
-      assert(pCols->numOfPoints == pBlock->numOfPoints);
+      SDataCols* pTSCol = pQueryHandle->rhelper.pDataCols[0];
+      assert(pTSCol->cols->type == TSDB_DATA_TYPE_TIMESTAMP && pTSCol->numOfPoints == pBlock->numOfPoints);
       
       if (pCheckInfo->lastKey > pBlock->keyFirst) {
         cur->pos =
-            binarySearchForKey(pCols->cols[0].pData, pBlock->numOfPoints, pCheckInfo->lastKey, pQueryHandle->order);
+            binarySearchForKey(pTSCol->cols[0].pData, pBlock->numOfPoints, pCheckInfo->lastKey, pQueryHandle->order);
       } else {
         cur->pos = 0;
       }
-
-      filterDataInDataBlock(pQueryHandle, pCheckInfo, pBlock, sa);
+      
+      mergeDataInDataBlock(pQueryHandle, pCheckInfo, pBlock, sa);
     } else {  // the whole block is loaded in to buffer
       pQueryHandle->realNumOfRows = pBlock->numOfPoints;
       cur->pos = 0;
@@ -486,7 +557,8 @@ static bool loadFileDataBlock(STsdbQueryHandle* pQueryHandle, SCompBlock* pBlock
         cur->pos = pBlock->numOfPoints - 1;
       }
       
-      filterDataInDataBlock(pQueryHandle, pCheckInfo, pBlock, sa);
+      
+      mergeDataInDataBlock(pQueryHandle, pCheckInfo, pBlock, sa);
     } else {
       pQueryHandle->realNumOfRows = pBlock->numOfPoints;
       cur->pos = pBlock->numOfPoints - 1;
@@ -559,87 +631,208 @@ static int vnodeBinarySearchKey(char* pValue, int num, TSKEY key, int order) {
   return midPos;
 }
 
+static int32_t copyDataFromFileBlock(STsdbQueryHandle* pQueryHandle, SDataBlockInfo* pBlockInfo, int32_t capacity,
+    int32_t numOfRows, int32_t* pos, int32_t endPos) {
+  char* pData = NULL;
+  SDataCols* pCols = pQueryHandle->rhelper.pDataCols[0];
+  TSKEY* tsArray = pCols->cols[0].pData;
+  
+  int32_t numOfCols = pCols->numOfCols;
+  
+  int32_t n = (*pos);  // todo: the output buffer limitation and the query time window?
+  while(n < pBlockInfo->rows && n <= endPos && ((n - (*pos) + numOfRows) < capacity)) { n++;}
+  
+  int32_t num = n - (*pos);
+  int32_t reqiredNumOfCols = taosArrayGetSize(pQueryHandle->pColumns);
+  
+  //data in buffer has greater timestamp, copy data in file block
+  for (int32_t i = 0; i < reqiredNumOfCols; ++i) {
+    SColumnInfoData* pColInfo = taosArrayGet(pQueryHandle->pColumns, i);
+    int32_t          bytes = pColInfo->info.bytes;
+    
+    if (ASCENDING_ORDER_TRAVERSE(pQueryHandle->order)) {
+      pData = pColInfo->pData + numOfRows * pColInfo->info.bytes;
+    } else {
+      pData = pColInfo->pData + (capacity - numOfRows - 1) * pColInfo->info.bytes;
+    }
+    
+    for (int32_t j = 0; j < 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 * (*pos), bytes * num);
+        } else {  // handle the var-string
+          char* dst = pData;
+          
+          // todo refactor, only copy one-by-one
+          for (int32_t k = (*pos); k < num + (*pos); ++k) {
+            char* p = tdGetColDataOfRow(src, k);
+            memcpy(dst, p, varDataTLen(p));
+            dst += bytes;
+          }
+        }
+        
+        break;
+      }
+    }
+  }
+  
+  *pos += num;
+  numOfRows += num;
+  
+  pQueryHandle->cur.win.ekey = tsArray[(*pos) - 1];
+  pQueryHandle->cur.lastKey = pQueryHandle->cur.win.ekey + 1; // todo ???
+  
+  return numOfRows;
+}
+
+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_ORDER_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 filterDataInDataBlock(STsdbQueryHandle* pQueryHandle, STableCheckInfo* pCheckInfo, SCompBlock* pBlock,
+static void mergeDataInDataBlock(STsdbQueryHandle* pQueryHandle, STableCheckInfo* pCheckInfo, SCompBlock* pBlock,
                                   SArray* sa) {
   SQueryFilePos* cur = &pQueryHandle->cur;
   SDataBlockInfo blockInfo = getTrueDataBlockInfo(pCheckInfo, pBlock);
   
+  initSkipListIterator(pQueryHandle, pCheckInfo);
   SDataCols* pCols = pQueryHandle->rhelper.pDataCols[0];
   
   int32_t endPos = cur->pos;
   if (ASCENDING_ORDER_TRAVERSE(pQueryHandle->order) && pQueryHandle->window.ekey > blockInfo.window.ekey) {
     endPos = blockInfo.rows - 1;
-    pQueryHandle->realNumOfRows = endPos - cur->pos + 1;
-    pCheckInfo->lastKey = blockInfo.window.ekey + 1;
   } else if (!ASCENDING_ORDER_TRAVERSE(pQueryHandle->order) && pQueryHandle->window.ekey < blockInfo.window.skey) {
     endPos = 0;
-    pQueryHandle->realNumOfRows = cur->pos + 1;
-    pCheckInfo->lastKey = blockInfo.window.ekey - 1;
   } else {
     int32_t order = (pQueryHandle->order == TSDB_ORDER_ASC)? TSDB_ORDER_DESC:TSDB_ORDER_ASC;
     endPos = vnodeBinarySearchKey(pCols->cols[0].pData, pCols->numOfPoints, pQueryHandle->window.ekey, order);
 
-    if (ASCENDING_ORDER_TRAVERSE(pQueryHandle->order)) {
-      if (endPos < cur->pos) {
-        pQueryHandle->realNumOfRows = 0;
-        return;
-      } else {
-        pQueryHandle->realNumOfRows = endPos - cur->pos + 1;
-      }
-
-      pCheckInfo->lastKey = ((int64_t*)(pCols->cols[0].pData))[endPos] + 1;
-    } else {
-      if (endPos > cur->pos) {
-        pQueryHandle->realNumOfRows = 0;
-        return;
-      } else {
-        pQueryHandle->realNumOfRows = cur->pos - endPos + 1;
-      }
-    }
+//    if (ASCENDING_ORDER_TRAVERSE(pQueryHandle->order)) {
+//      if (endPos < cur->pos) {
+//        pQueryHandle->realNumOfRows = 0;
+//        return;
+//      } else {
+//        pQueryHandle->realNumOfRows = endPos - cur->pos + 1;
+//      }
+//
+//      pCheckInfo->lastKey = ((int64_t*)(pCols->cols[0].pData))[endPos] + 1;
+//    } else {
+//      if (endPos > cur->pos) {
+//        pQueryHandle->realNumOfRows = 0;
+//        return;
+//      } else {
+//        pQueryHandle->realNumOfRows = cur->pos - endPos + 1;
+//      }
+//    }
   }
-
-  int32_t start = MIN(cur->pos, endPos);
   
-//  if (start > 0) {
-//    tdPopDataColsPoints(pQueryHandle->rhelper.pDataCols[0], start);
-//  }
-
-  // move the data block in the front to data block if needed
-  int32_t numOfCols = pQueryHandle->rhelper.pDataCols[0]->numOfCols;
-  int32_t reqCols = taosArrayGetSize(pQueryHandle->pColumns);
+  // compared with the data from in-memory buffer, to generate the correct timestamp array list
+  int32_t pos = MIN(cur->pos, endPos);
   
-  for (int32_t i = 0; i < reqCols; ++i) {
-    SColumnInfoData* pCol = taosArrayGet(pQueryHandle->pColumns, i);
-    int32_t bytes = pCol->info.bytes;
-
-    for (int32_t j = 0; j < numOfCols; ++j) {  //todo opt performance
-      SDataCol* src = &pQueryHandle->rhelper.pDataCols[0]->cols[j];
-
-      if (pCol->info.colId == src->colId) {
-        if (pCol->info.type != TSDB_DATA_TYPE_BINARY && pCol->info.type != TSDB_DATA_TYPE_NCHAR) {
-          memmove(pCol->pData, src->pData + bytes * start, bytes * pQueryHandle->realNumOfRows);
-        } else { // handle the var-string
-          char* dst = pCol->pData;
+  assert(pCols->cols[0].type == TSDB_DATA_TYPE_TIMESTAMP && pCols->cols[0].colId == 0);
+  TSKEY* tsArray = pCols->cols[0].pData;
   
-          // todo refactor, only copy one-by-one
-          for(int32_t k = start; k < pQueryHandle->realNumOfRows + start; ++k) {
-            char* p = tdGetColDataOfRow(src, k);
-            memcpy(dst, p, varDataTLen(p));
-            dst += bytes;
-          }
+  int32_t numOfRows = 0;
+  pQueryHandle->cur.win = TSWINDOW_INITIALIZER;
+  
+  // no data in buffer, load data from file directly
+  if (pCheckInfo->iiter == NULL && pCheckInfo->iter == NULL) {
+    cur->win.skey = tsArray[pos];
+    copyDataFromFileBlock(pQueryHandle, &blockInfo, pQueryHandle->outputCapacity, numOfRows, &pos, endPos);
+    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);
+  
+    while (1) {
+      SSkipListNode* node = tSkipListIterGet(pCheckInfo->iter);
+      if (node == NULL) {
+        if (cur->win.skey == TSKEY_INITIAL_VAL) {
+          cur->win.skey = tsArray[pos];
         }
         
+        numOfRows = copyDataFromFileBlock(pQueryHandle, &blockInfo, pQueryHandle->outputCapacity, numOfRows, &pos, endPos);
         break;
       }
+  
+      SDataRow row = SL_GET_NODE_DATA(node);
+      TSKEY    key = dataRowKey(row);
+      
+      if (key < tsArray[pos]) {
+        copyOneRowFromMem(pQueryHandle, pCheckInfo, pQueryHandle->outputCapacity, numOfRows, row, pSchema);
+        numOfRows += 1;
+        cur->mixBlock = true;
+        
+        if (cur->win.skey == TSKEY_INITIAL_VAL) {
+          cur->win.skey = key;
+        }
+        
+        cur->win.ekey = key;
+        tSkipListIterNext(pCheckInfo->iter);
+        
+        if (numOfRows >= pQueryHandle->outputCapacity) {
+          break;
+        }
+      } 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]) {
+        if (cur->win.skey == TSKEY_INITIAL_VAL) {
+          cur->win.skey = tsArray[pos];
+        }
+        
+        numOfRows = copyDataFromFileBlock(pQueryHandle, &blockInfo, pQueryHandle->outputCapacity, numOfRows, &pos, endPos);
+        
+        if (numOfRows >= pQueryHandle->outputCapacity ||
+            pQueryHandle->cur.lastKey >= blockInfo.window.ekey ||
+            pQueryHandle->cur.lastKey > pQueryHandle->window.ekey) {
+          break;
+        }
+      }
     }
   }
 
-  assert(pQueryHandle->realNumOfRows <= blockInfo.rows);
+  pCheckInfo->lastKey = cur->lastKey;
+  pQueryHandle->realNumOfRows = numOfRows;
+  cur->rows = numOfRows;
+  cur->pos = pos;
 
-  // forward(backward) the position for cursor
-  cur->pos = endPos;
+  uTrace("%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) {
@@ -879,7 +1072,7 @@ static bool getDataBlocksInFilesImpl(STsdbQueryHandle* pQueryHandle) {
   // no data in file anymore
   if (pQueryHandle->numOfBlocks <= 0) {
     assert(pQueryHandle->pFileGroup == NULL);
-    cur->fid = -1;
+    cur->fid = -1;  // denote that there are no data in file anymore
     
     return false;
   }
@@ -888,10 +1081,7 @@ static bool getDataBlocksInFilesImpl(STsdbQueryHandle* pQueryHandle) {
   cur->fid = pQueryHandle->pFileGroup->fileId;
   
   STableBlockInfo* pBlockInfo = &pQueryHandle->pDataBlockInfo[cur->slot];
-  STableCheckInfo* pCheckInfo = pBlockInfo->pTableCheckInfo;
-  SCompBlock*      pBlock = pBlockInfo->pBlock.compBlock;
-  
-  return loadFileDataBlock(pQueryHandle, pBlock, pCheckInfo);
+  return loadFileDataBlock(pQueryHandle, pBlockInfo->pBlock.compBlock, pBlockInfo->pTableCheckInfo);
 }
 
 static bool getDataBlocksInFiles(STsdbQueryHandle* pQueryHandle) {
@@ -901,30 +1091,34 @@ static bool getDataBlocksInFiles(STsdbQueryHandle* pQueryHandle) {
   // find the start data block in file
   if (!pQueryHandle->locateStart) {
     pQueryHandle->locateStart = true;
-
-    int32_t fid = getFileIdFromKey(pQueryHandle->window.skey);
+    int32_t fid = getFileIdFromKey(pQueryHandle->window.skey, pQueryHandle->pTsdb->config.daysPerFile);
     
     tsdbInitFileGroupIter(pFileHandle, &pQueryHandle->fileIter, pQueryHandle->order);
     tsdbSeekFileGroupIter(&pQueryHandle->fileIter, fid);
 
     return getDataBlocksInFilesImpl(pQueryHandle);
   } else {
-    if ((cur->slot == pQueryHandle->numOfBlocks - 1 && ASCENDING_ORDER_TRAVERSE(pQueryHandle->order)) ||
-        (cur->slot == 0 && !ASCENDING_ORDER_TRAVERSE(pQueryHandle->order))) { // all blocks
-      
-      return getDataBlocksInFilesImpl(pQueryHandle);
-    } else {  // next block of the same file
-      int32_t step = ASCENDING_ORDER_TRAVERSE(pQueryHandle->order)? 1:-1;
-      cur->slot += step;
-      
-      STableBlockInfo* pBlockInfo = &pQueryHandle->pDataBlockInfo[cur->slot];
-      if (ASCENDING_ORDER_TRAVERSE(pQueryHandle->order)) {
-        cur->pos = 0;
-      } else {
-        cur->pos = pBlockInfo->pBlock.compBlock->numOfPoints - 1;
+    // 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->pos >= pBlockInfo->pBlock.compBlock->numOfPoints) {
+      if ((cur->slot == pQueryHandle->numOfBlocks - 1 && ASCENDING_ORDER_TRAVERSE(pQueryHandle->order)) ||
+          (cur->slot == 0 && !ASCENDING_ORDER_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_ORDER_TRAVERSE(pQueryHandle->order) ? 1 : -1;
+        cur->slot += step;
+
+        STableBlockInfo* pNext = &pQueryHandle->pDataBlockInfo[cur->slot];
+        return loadFileDataBlock(pQueryHandle, pNext->pBlock.compBlock, pNext->pTableCheckInfo);
       }
-
-      return loadFileDataBlock(pQueryHandle, pBlockInfo->pBlock.compBlock, pBlockInfo->pTableCheckInfo);
+    } else {
+      SArray* sa = getDefaultLoadColumns(pQueryHandle, true);
+      mergeDataInDataBlock(pQueryHandle, pCheckInfo, pBlockInfo->pBlock.compBlock, sa);
+      return pQueryHandle->pColumns;
     }
   }
 }
@@ -1032,7 +1226,7 @@ static int tsdbReadRowsFromCache(SSkipListIterator* pIter, STable* pTable, TSKEY
                                  STsdbQueryHandle* pQueryHandle) {
   int     numOfRows = 0;
   int32_t numOfCols = taosArrayGetSize(pQueryHandle->pColumns);
-  *skey = INT64_MIN;
+  *skey = TSKEY_INITIAL_VAL;
 
   do {
     SSkipListNode* node = tSkipListIterGet(pIter);
@@ -1117,34 +1311,89 @@ SDataBlockInfo tsdbRetrieveDataBlockInfo(TsdbQueryHandleT* pQueryHandle) {
   STsdbQueryHandle* pHandle = (STsdbQueryHandle*)pQueryHandle;
 
   STable* pTable = NULL;
-
-  TSKEY   skey = 0, ekey = 0;
   int32_t rows = 0;
 
   int32_t step = ASCENDING_ORDER_TRAVERSE(pHandle->order)? 1:-1;
   
-  // data in file
+  // there are data in file
   if (pHandle->cur.fid >= 0) {
     STableBlockInfo* pBlockInfo = &pHandle->pDataBlockInfo[pHandle->cur.slot];
+    STableCheckInfo* pCheckInfo = pBlockInfo->pTableCheckInfo;
 
-    pTable = pBlockInfo->pTableCheckInfo->pTableObj;
-
-    SDataBlockInfo binfo = getTrueDataBlockInfo(pBlockInfo->pTableCheckInfo, pBlockInfo->pBlock.compBlock);
-    if (binfo.rows == pHandle->realNumOfRows) {
-      pBlockInfo->pTableCheckInfo->lastKey = pBlockInfo->pBlock.compBlock->keyLast + 1;
-      return binfo;
+    pTable = pCheckInfo->pTableObj;
+    
+    SDataBlockInfo binfo = getTrueDataBlockInfo(pCheckInfo, pBlockInfo->pBlock.compBlock);
+    /*bool hasData = */initSkipListIterator(pHandle, pCheckInfo);
+    
+    TSKEY k1 = TSKEY_INITIAL_VAL, k2 = TSKEY_INITIAL_VAL;
+    if (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) {
+      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;
+        }
+      }
+    }
+    
+    assert(0);
+    if ((k1 != TSKEY_INITIAL_VAL && k1 < binfo.window.ekey) || (k2 != TSKEY_INITIAL_VAL && k2 < binfo.window.ekey)) {
+      doLoadFileDataBlock(pHandle, pBlockInfo->pBlock.compBlock, pCheckInfo);
+
+      SArray* sa = getDefaultLoadColumns(pHandle, true);
+      mergeDataInDataBlock(pHandle, pCheckInfo, pBlockInfo->pBlock.compBlock, sa);
+      taosArrayDestroy(sa);
+  
+      SDataBlockInfo blockInfo = {
+          .uid = pTable->tableId.uid,
+          .tid = pTable->tableId.tid,
+          .rows = pHandle->cur.rows,
+          .window = pHandle->cur.win,
+      };
+  
+      return blockInfo;
     } else {
-      /* not a whole disk block, only the qualified rows, so this block is loaded in to buffer during the
-       * block next function
+      /*
+       * no data in mem or imem, or data in mem|imem with greater timestamp, no need to load data in buffer
+       * return the file block info directly
        */
-      SColumnInfoData* pColInfoEx = taosArrayGet(pHandle->pColumns, 0);
-
-      rows = pHandle->realNumOfRows;
-      skey = *(TSKEY*)pColInfoEx->pData;
-      ekey = *(TSKEY*)((char*)pColInfoEx->pData + TSDB_KEYSIZE * (rows - 1));
-
-      // update the last key value
-      pBlockInfo->pTableCheckInfo->lastKey = ekey + step;
+      if (!pHandle->cur.mixBlock && pHandle->cur.rows == pBlockInfo->pBlock.compBlock->numOfPoints) {
+        pBlockInfo->pTableCheckInfo->lastKey = pBlockInfo->pBlock.compBlock->keyLast + step;
+        assert(pHandle->outputCapacity >= pBlockInfo->pBlock.compBlock->numOfPoints);
+        
+        return binfo;
+      } else {
+        SDataBlockInfo blockInfo = {
+            .uid = pTable->tableId.uid,
+            .tid = pTable->tableId.tid,
+            .rows = pHandle->cur.rows,
+            .window = pHandle->cur.win,
+        };
+        
+        return blockInfo;
+      }
     }
   } else {
     STableCheckInfo* pCheckInfo = taosArrayGet(pHandle->pTableCheckInfo, pHandle->activeIndex);
@@ -1153,21 +1402,24 @@ SDataBlockInfo tsdbRetrieveDataBlockInfo(TsdbQueryHandleT* pQueryHandle) {
     if (pTable->mem != NULL) {
       // create mem table iterator if it is not created yet
       assert(pCheckInfo->iter != NULL);
-      rows = tsdbReadRowsFromCache(pCheckInfo->iter, pCheckInfo->pTableObj, pHandle->window.ekey, 4000, &skey, &ekey, pHandle);
+      STimeWindow* win = &pHandle->cur.win;
+      
+      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 = ekey + step;
+      pCheckInfo->lastKey = win->ekey + step;
     }
+  
+    SDataBlockInfo blockInfo = {
+        .uid = pTable->tableId.uid,
+        .tid = pTable->tableId.tid,
+        .rows = rows,
+        .window = pHandle->cur.win,
+    };
+  
+    return blockInfo;
   }
-
-  SDataBlockInfo blockInfo = {
-      .uid = pTable->tableId.uid,
-      .tid = pTable->tableId.tid,
-      .rows = rows,
-      .window = {.skey = MIN(skey, ekey), .ekey = MAX(skey, ekey)}
-  };
-
-  return blockInfo;
 }
 
 // return null for data block in cache
@@ -1189,12 +1441,12 @@ SArray* tsdbRetrieveDataBlock(TsdbQueryHandleT* pQueryHandle, SArray* pIdList) {
     STableBlockInfo* pBlockInfoEx = &pHandle->pDataBlockInfo[pHandle->cur.slot];
     STableCheckInfo* pCheckInfo = pBlockInfoEx->pTableCheckInfo;
 
-    SDataBlockInfo binfo = getTrueDataBlockInfo(pCheckInfo, pBlockInfoEx->pBlock.compBlock);
-    assert(pHandle->realNumOfRows <= binfo.rows);
-
-    if (pHandle->realNumOfRows < binfo.rows) {
+    if (pHandle->cur.mixBlock) {
       return pHandle->pColumns;
     } else {
+      SDataBlockInfo binfo = getTrueDataBlockInfo(pCheckInfo, pBlockInfoEx->pBlock.compBlock);
+      assert(pHandle->realNumOfRows <= binfo.rows);
+  
       // data block has been loaded, todo extract method
       SDataBlockLoadInfo* pBlockLoadInfo = &pHandle->dataBlockLoadInfo;
       
@@ -1206,7 +1458,7 @@ SArray* tsdbRetrieveDataBlock(TsdbQueryHandleT* pQueryHandle, SArray* pIdList) {
         doLoadFileDataBlock(pHandle, pBlock, pCheckInfo);
 
         SArray* sa = getDefaultLoadColumns(pHandle, true);
-        filterDataInDataBlock(pHandle, pCheckInfo, pBlock, sa);
+        mergeDataInDataBlock(pHandle, pCheckInfo, pBlock, sa);
         taosArrayDestroy(sa);
 
         return pHandle->pColumns;
@@ -1631,7 +1883,7 @@ void tsdbCleanupQueryHandle(TsdbQueryHandleT queryHandle) {
    size_t cols = taosArrayGetSize(pQueryHandle->pColumns);
    for (int32_t i = 0; i < cols; ++i) {
      SColumnInfoData* pColInfo = taosArrayGet(pQueryHandle->pColumns, i);
-      tfree(pColInfo->pData);
+     tfree(pColInfo->pData);
    }
 
   taosArrayDestroy(pQueryHandle->pColumns);
diff --git a/tests/examples/c/demo.c b/tests/examples/c/demo.c
index 70b1b2067f43c11a734a6a13dfec997a6971398b..76bfa5949e4a09afecc6f8c3bba5a408551cc84b 100644
--- a/tests/examples/c/demo.c
+++ b/tests/examples/c/demo.c
@@ -74,9 +74,8 @@ int main(int argc, char *argv[]) {
   printf("success to connect to server\n");
   
   doQuery(taos, "create database if not exists test");
-  doQuery(taos, "create database if not exists test");
-//  doQuery(taos, "use test");
-//  doQuery(taos, "select sum(k)*max(k), sum(k), max(k) from tm99");
+  doQuery(taos, "use test");
+  doQuery(taos, "select count(*) from m1 where ts>='2020-1-1 1:1:1' and ts<='2020-1-1 1:1:59' interval(500a) fill(value, 99)");
   
 //  doQuery(taos, "create table t1(ts timestamp, k binary(12), f nchar(2))");
 //  for(int32_t i = 0; i< 100000; ++i) {