Merge pull request #9554 from taosdata/fix/TS-445-V24

[TS-445]<fix>(query):Limit offset optimition of performance

src/inc/tsdb.h

@@ -173,6 +173,7 @@ typedef void *TsdbQueryHandleT;  // Use void to hide implementation details
 typedef struct STsdbQueryCond {
   STimeWindow  twindow;
   int32_t      order;             // desc|asc order to iterate the data block
+  int64_t      offset;            // skip offset put down to tsdb
   int32_t      numOfCols;
   SColumnInfo *colList;
   bool         loadExternalRows;  // load external rows or not
@@ -391,6 +392,9 @@ void tsdbResetQueryHandleForNewTable(TsdbQueryHandleT queryHandle, STsdbQueryCon
 
 int32_t tsdbGetFileBlocksDistInfo(TsdbQueryHandleT* queryHandle, STableBlockDist* pTableBlockInfo);
 
+// obtain queryHandle attribute
+int64_t tsdbSkipOffset(TsdbQueryHandleT queryHandle);
+
 /**
  * get the statistics of repo usage
  * @param repo. point to the tsdbrepo

src/query/inc/qExecutor.h

@@ -237,6 +237,7 @@ typedef struct SQueryAttr {
   bool             createFilterOperator; // if filter operator is needed
   bool             multigroupResult; // multigroup result can exist in one SSDataBlock
   bool             needSort;         // need sort rowRes
+  bool             skipOffset;       // can skip offset if true 
   int32_t          interBufSize;     // intermediate buffer sizse
 
   int32_t          havingNum;        // having expr number

src/query/src/qExecutor.c

@@ -4905,6 +4905,11 @@ STsdbQueryCond createTsdbQueryCond(SQueryAttr* pQueryAttr, STimeWindow* win) {
       .loadExternalRows = false,
   };
 
+  // set offset with
+  if(pQueryAttr->skipOffset) {
+     cond.offset = pQueryAttr->limit.offset;
+  }
+
   TIME_WINDOW_COPY(cond.twindow, *win);
   return cond;
 }
@@ -5858,19 +5863,38 @@ static SSDataBlock* doLimit(void* param, bool* newgroup) {
       return NULL;
     }
 
+    bool move = false;
+    int32_t skip = 0;
+    int32_t remain = 0;
+    int64_t srows  = tsdbSkipOffset(pRuntimeEnv->pQueryHandle);
+
     if (pRuntimeEnv->currentOffset == 0) {
       break;
+    }
+    else if(srows > 0) {
+      if(pRuntimeEnv->currentOffset - srows >= pBlock->info.rows) {
+        pRuntimeEnv->currentOffset -= pBlock->info.rows;
+      } else {
+        move   = true;
+        skip   = (int32_t)(pRuntimeEnv->currentOffset - srows);
+        remain = (int32_t)(pBlock->info.rows - skip);
+      }
     } else if (pRuntimeEnv->currentOffset >= pBlock->info.rows) {
       pRuntimeEnv->currentOffset -= pBlock->info.rows;
     } else {
-      int32_t remain = (int32_t)(pBlock->info.rows - pRuntimeEnv->currentOffset);
+      move   = true;
+      skip   = (int32_t)pRuntimeEnv->currentOffset;
+      remain = (int32_t)(pBlock->info.rows - pRuntimeEnv->currentOffset);
+    }
+    
+    // need move
+    if(move) {
       pBlock->info.rows = remain;
-
       for (int32_t i = 0; i < pBlock->info.numOfCols; ++i) {
         SColumnInfoData* pColInfoData = taosArrayGet(pBlock->pDataBlock, i);
 
         int16_t bytes = pColInfoData->info.bytes;
-        memmove(pColInfoData->pData, pColInfoData->pData + bytes * pRuntimeEnv->currentOffset, remain * bytes);
+        memmove(pColInfoData->pData, pColInfoData->pData + skip * bytes, remain * bytes);
       }
 
       pRuntimeEnv->currentOffset = 0;

src/tsdb/src/tsdbRead.c

@@ -39,6 +39,9 @@
                     .tid = (_checkInfo)->tableId.tid,                                  \
                     .uid = (_checkInfo)->tableId.uid})
 
+// limit offset start optimization for rows read over this value
+#define OFFSET_SKIP_THRESHOLD 5000
+
 enum {
   TSDB_QUERY_TYPE_ALL      = 1,
   TSDB_QUERY_TYPE_LAST     = 2,
@@ -117,6 +120,9 @@ typedef struct STsdbQueryHandle {
   STsdbRepo*     pTsdb;
   SQueryFilePos  cur;              // current position
   int16_t        order;
+  int64_t        offset;           // limit offset
+  int64_t        srows;            // skip offset rows
+  int64_t        frows;            // forbid skip offset rows
   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;
@@ -155,6 +161,11 @@ typedef struct STableGroupSupporter {
   STSchema*  pTagSchema;
 } STableGroupSupporter;
 
+typedef struct SRange {
+  int32_t from;
+  int32_t to;
+} SRange;
+
 static STimeWindow updateLastrowForEachGroup(STableGroupInfo *groupList);
 static int32_t checkForCachedLastRow(STsdbQueryHandle* pQueryHandle, STableGroupInfo *groupList);
 static int32_t checkForCachedLast(STsdbQueryHandle* pQueryHandle);
@@ -413,6 +424,9 @@ static STsdbQueryHandle* tsdbQueryTablesImpl(STsdbRepo* tsdb, STsdbQueryCond* pC
   }
 
   pQueryHandle->order       = pCond->order;
+  pQueryHandle->offset      = pCond->offset;
+  pQueryHandle->srows       = 0;
+  pQueryHandle->frows       = 0;
   pQueryHandle->pTsdb       = tsdb;
   pQueryHandle->type        = TSDB_QUERY_TYPE_ALL;
   pQueryHandle->cur.fid     = INT32_MIN;
@@ -529,6 +543,9 @@ void tsdbResetQueryHandle(TsdbQueryHandleT queryHandle, STsdbQueryCond *pCond) {
   }
 
   pQueryHandle->order       = pCond->order;
+  pQueryHandle->offset      = pCond->offset;
+  pQueryHandle->srows       = 0;
+  pQueryHandle->frows       = 0;
   pQueryHandle->window      = pCond->twindow;
   pQueryHandle->type        = TSDB_QUERY_TYPE_ALL;
   pQueryHandle->cur.fid     = -1;
@@ -1073,63 +1090,302 @@ static int32_t binarySearchForBlock(SBlock* pBlock, int32_t numOfBlocks, TSKEY s
   return midSlot;
 }
 
-static int32_t loadBlockInfo(STsdbQueryHandle * pQueryHandle, int32_t index, int32_t* numOfBlocks) {
-  int32_t code = 0;
+// array :1 2 3 5 7 -2 (8 9) skip 4 and 6
+int32_t memMoveByArray(SBlock *blocks, SArray *pArray) {
+  // pArray is NULL or size is zero , no need block to move 
+  if(pArray == NULL)
+    return 0;
+  size_t count = taosArrayGetSize(pArray);
+  if(count == 0)
+    return 0;
 
-  STableCheckInfo* pCheckInfo = taosArrayGet(pQueryHandle->pTableCheckInfo, index);
-  pCheckInfo->numOfBlocks = 0;
+  // memmove
+  int32_t num = 0;
+  SRange* ranges = (SRange*)TARRAY_GET_START(pArray);
+  for(size_t i = 0; i < count; i++) {
+    int32_t step = ranges[i].to - ranges[i].from + 1;
+    memmove(blocks + num, blocks + ranges[i].from, sizeof(SBlock) * step);
+    num += step;
+  }
 
-  if (tsdbSetReadTable(&pQueryHandle->rhelper, pCheckInfo->pTableObj) != TSDB_CODE_SUCCESS) {
-    code = terrno;
-    return code;
+  return num;
+}
+
+// if block data in memory return false else true
+bool blockNoItemInMem(STsdbQueryHandle* q, SBlock* pBlock) {
+  if(q->pMemRef == NULL) {
+    return false;
   }
 
-  SBlockIdx* compIndex = pQueryHandle->rhelper.pBlkIdx;
+  // mem
+  if(q->pMemRef->snapshot.mem) {
+    SMemTable* mem = q->pMemRef->snapshot.mem;
+    if(timeIntersect(mem->keyFirst, mem->keyLast, pBlock->keyFirst, pBlock->keyLast))
+      return false;
+  }
+  // imem
+  if(q->pMemRef->snapshot.imem) {
+    SMemTable* imem = q->pMemRef->snapshot.imem;
+    if(timeIntersect(imem->keyFirst, imem->keyLast, pBlock->keyFirst, pBlock->keyLast))
+      return false;
+  }
 
-  // no data block in this file, try next file
-  if (compIndex == NULL || compIndex->uid != pCheckInfo->tableId.uid) {
-    return 0;  // no data blocks in the file belongs to pCheckInfo->pTable
+  return true;
+}
+
+#define MAYBE_IN_MEMORY_ROWS 4000  // approximately the capacity of one block
+// skip blocks . return value is skip blocks number, skip rows reduce from *pOffset
+static int32_t offsetSkipBlock(STsdbQueryHandle* q, SBlockInfo* pBlockInfo, int64_t skey, int64_t ekey,
+                              int32_t sblock, int32_t eblock, SArray** ppArray, bool order) {
+  int32_t num = 0;
+  SBlock* blocks = pBlockInfo->blocks;
+  SArray* pArray = NULL;
+  SRange range;
+  range.from = -1;
+
+  //
+  // ASC
+  //
+  if(order) {
+    for(int32_t i = sblock; i < eblock; i++) {
+      bool skip = false;
+      SBlock* pBlock = &blocks[i];
+      if(i == sblock && skey > pBlock->keyFirst) {
+        q->frows += pBlock->numOfRows;  // some rows time < s
+      } else {
+        // check can skip
+        if(q->srows + q->frows + pBlock->numOfRows + MAYBE_IN_MEMORY_ROWS < q->offset) { // approximately calculate
+          if(blockNoItemInMem(q, pBlock)) {
+            // can skip
+            q->srows += pBlock->numOfRows;
+            skip = true;
+          } else {
+            q->frows += pBlock->numOfRows; // maybe have some row in memroy
+          }
+        } else {
+          // the remainder be put to pArray
+          if(pArray == NULL)
+              pArray = taosArrayInit(1, sizeof(SRange));
+          if(range.from == -1) {
+            range.from = i;
+          } else {
+            if(range.to + 1 != i) {
+              // add the previous
+              taosArrayPush(pArray, &range);
+              range.from = i;
+            }
+          }
+          range.to = eblock - 1;
+          taosArrayPush(pArray, &range);
+          range.from = -1;
+          break;
+        }
+      }
+
+      if(skip) {
+        num ++;
+      } else {
+        // can't skip, append block index to pArray
+        if(pArray == NULL)
+            pArray = taosArrayInit(10, sizeof(SRange));
+        if(range.from == -1) {
+          range.from = i;
+        } else {
+          if(range.to + 1 != i) {
+            // add the previous
+            taosArrayPush(pArray, &range);
+            range.from = i;
+          }
+        }
+        range.to = i;
+      }
+    }
+    // end append
+    if(range.from != -1) {
+      if(pArray == NULL)
+          pArray = taosArrayInit(1, sizeof(SRange));
+      taosArrayPush(pArray, &range);
+    }
+
+    // ASC return
+    *ppArray = pArray;
+    return num;
   }
+  
+  // DES
+  for(int32_t i = eblock - 1; i >= sblock; i--) {
+    bool skip = false;
+    SBlock* pBlock = &blocks[i];
+    if(i == eblock - 1 && ekey < pBlock->keyLast) {
+      q->frows += pBlock->numOfRows; // some rows time > e
+    } else {
+      // check can skip
+      if(q->srows + q->frows + pBlock->numOfRows + MAYBE_IN_MEMORY_ROWS < q->offset) { // approximately calculate
+        if(blockNoItemInMem(q, pBlock)) {
+          // can skip
+          q->srows += pBlock->numOfRows;
+          skip = true;
+        } else {
+          q->frows += pBlock->numOfRows; // maybe have some row in memroy
+        }
+      } else {
+          // the remainder be put to pArray
+          if(pArray == NULL)
+              pArray = taosArrayInit(1, sizeof(SRange));
+          if(range.from == -1) {
+            range.from = i;
+          } else {
+            if(range.to - 1 != i) {
+              // add the previous
+              taosArrayPush(pArray, &range);
+              range.from = i;
+            }
+          }
+          range.to = 0;
+          taosArrayPush(pArray, &range);
+          range.from = -1;
+          break;
+      }
+    }
 
-  assert(compIndex->len > 0);
+    if(skip) {
+      num ++;
+    } else {
+      // can't skip, append block index to pArray
+      if(pArray == NULL)
+          pArray = taosArrayInit(10, sizeof(SRange));
+      if(range.from == -1) {
+        range.from = i;
+      } else {
+        if(range.to + 1 != i) {
+          // add the previous
+          taosArrayPush(pArray, &range);
+          range.from = i;
+        }
+      }
+      range.to = i;
+    }
+  }
 
-  if (tsdbLoadBlockInfo(&(pQueryHandle->rhelper), (void**)(&pCheckInfo->pCompInfo),
-                        (uint32_t*)(&pCheckInfo->compSize)) < 0) {
-    return terrno;
+  // end append
+  if(range.from != -1) {
+    if(pArray == NULL)
+        pArray = taosArrayInit(1, sizeof(SRange));
+    taosArrayPush(pArray, &range);
   }
-  SBlockInfo* pCompInfo = pCheckInfo->pCompInfo;
+  if(pArray == NULL)
+    return num;
 
-  TSKEY s = TSKEY_INITIAL_VAL, e = TSKEY_INITIAL_VAL;
+  // reverse array
+  size_t count = taosArrayGetSize(pArray);
+  SRange* ranges = TARRAY_GET_START(pArray);
+  SArray* pArray1 = taosArrayInit(count, sizeof(SRange));
 
-  if (ASCENDING_TRAVERSE(pQueryHandle->order)) {
+  size_t i = count - 1;
+  while(i >= 0) {
+    range.from = ranges[i].to;
+    range.to   = ranges[i].from;
+    taosArrayPush(pArray1, &range);
+    if(i == 0)
+      break;
+    i --;
+  }
+
+  *ppArray = pArray1;
+  taosArrayDestroy(&pArray);
+  return num;
+}
+
+// shrink blocks by condition of query
+static void shrinkBlocksByQuery(STsdbQueryHandle *pQueryHandle, STableCheckInfo *pCheckInfo) {
+  SBlockInfo *pCompInfo = pCheckInfo->pCompInfo;
+  SBlockIdx  *compIndex = pQueryHandle->rhelper.pBlkIdx;
+  bool order = ASCENDING_TRAVERSE(pQueryHandle->order);
+
+  if (order) {
     assert(pCheckInfo->lastKey <= pQueryHandle->window.ekey && pQueryHandle->window.skey <= pQueryHandle->window.ekey);
   } else {
     assert(pCheckInfo->lastKey >= pQueryHandle->window.ekey && pQueryHandle->window.skey >= pQueryHandle->window.ekey);
   }
 
+  TSKEY s = TSKEY_INITIAL_VAL, e = TSKEY_INITIAL_VAL;
   s = MIN(pCheckInfo->lastKey, pQueryHandle->window.ekey);
   e = MAX(pCheckInfo->lastKey, pQueryHandle->window.ekey);
 
   // discard the unqualified data block based on the query time window
   int32_t start = binarySearchForBlock(pCompInfo->blocks, compIndex->numOfBlocks, s, TSDB_ORDER_ASC);
-  int32_t end = start;
-
   if (s > pCompInfo->blocks[start].keyLast) {
-    return 0;
+    return ;
   }
 
-  // todo speedup the procedure of located end block
+  int32_t end = start;
+  // locate e index of blocks -> end
   while (end < (int32_t)compIndex->numOfBlocks && (pCompInfo->blocks[end].keyFirst <= e)) {
     end += 1;
   }
 
-  pCheckInfo->numOfBlocks = (end - start);
+  // calc offset can skip blocks number
+  int32_t nSkip = 0;
+  SArray *pArray = NULL;
+  if(pQueryHandle->offset > 0) {
+     nSkip = offsetSkipBlock(pQueryHandle, pCompInfo, s, e, start, end, &pArray, order);
+  }
+
+  if(nSkip > 0) { // have offset and can skip
+    pCheckInfo->numOfBlocks = memMoveByArray(pCompInfo->blocks, pArray);
+  } else { // no offset
+    pCheckInfo->numOfBlocks = end - start;
+    if(start > 0)
+      memmove(pCompInfo->blocks, &pCompInfo->blocks[start], pCheckInfo->numOfBlocks * sizeof(SBlock));
+  }
+
+  if(pArray)
+    taosArrayDestroy(&pArray);
+}
+
+// load one table (tsd_index point to) need load blocks info and put into pCheckInfo->pCompInfo->blocks
+static int32_t loadBlockInfo(STsdbQueryHandle * pQueryHandle, int32_t tsd_index, int32_t* numOfBlocks) {
+  //
+  // ONE PART. Load all blocks info from one table of tsd_index
+  //
+  int32_t code = 0;
+  STableCheckInfo* pCheckInfo = taosArrayGet(pQueryHandle->pTableCheckInfo, tsd_index);
+  pCheckInfo->numOfBlocks = 0;
+  if (tsdbSetReadTable(&pQueryHandle->rhelper, pCheckInfo->pTableObj) != TSDB_CODE_SUCCESS) {
+    code = terrno;
+    return code;
+  }
+
+  SBlockIdx* compIndex = pQueryHandle->rhelper.pBlkIdx;
+  // no data block in this file, try next file
+  if (compIndex == NULL || compIndex->uid != pCheckInfo->tableId.uid) {
+    return 0;  // no data blocks in the file belongs to pCheckInfo->pTable
+  }
 
-  if (start > 0) {
-    memmove(pCompInfo->blocks, &pCompInfo->blocks[start], pCheckInfo->numOfBlocks * sizeof(SBlock));
+  if (pCheckInfo->compSize < (int32_t)compIndex->len) {
+    assert(compIndex->len > 0);
+    char* t = realloc(pCheckInfo->pCompInfo, compIndex->len);
+    if (t == NULL) {
+      terrno = TSDB_CODE_TDB_OUT_OF_MEMORY;
+      code = TSDB_CODE_TDB_OUT_OF_MEMORY;
+      return code;
+    }
+
+    pCheckInfo->pCompInfo = (SBlockInfo*)t;
+    pCheckInfo->compSize = compIndex->len;
+  }
+
+  if (tsdbLoadBlockInfo(&(pQueryHandle->rhelper), (void**)(&pCheckInfo->pCompInfo),
+                        (uint32_t*)(&pCheckInfo->compSize)) < 0) {
+    return terrno;
   }
 
+  //
+  // TWO PART. shrink no need blocks from all blocks by condition of query
+  //
+  shrinkBlocksByQuery(pQueryHandle, pCheckInfo);
   (*numOfBlocks) += pCheckInfo->numOfBlocks;
+
   return 0;
 }
 
@@ -4312,4 +4568,11 @@ end:
   return string;
 }
 
-
+// obtain queryHandle attribute
+int64_t tsdbSkipOffset(TsdbQueryHandleT queryHandle) {
+  STsdbQueryHandle* pQueryHandle = (STsdbQueryHandle*)queryHandle;
+  if (pQueryHandle) {
+    return pQueryHandle->srows;
+  }
+  return 0;
+}

src/util/inc/tutil.h

@@ -58,6 +58,13 @@ static FORCE_INLINE void taosEncryptPass(uint8_t *inBuf, size_t inLen, char *tar
   memcpy(target, context.digest, TSDB_KEY_LEN);
 }
 
+//
+// TSKEY util
+//
+
+// if time area(s1,e1) intersect with time area(s2,e2) then return true else return false
+bool timeIntersect(TSKEY s1, TSKEY e1, TSKEY s2, TSKEY e2);
+
 #ifdef __cplusplus
 }
 #endif

src/util/src/tutil.c

@@ -549,3 +549,16 @@ FORCE_INLINE double taos_align_get_double(const char* pBuf) {
   memcpy(&dv, pBuf, sizeof(dv)); // in ARM, return *((const double*)(pBuf)) may cause problem
   return dv; 
 }
+
+//
+// TSKEY util
+//
+
+// if time area(s1,e1) intersect with time area(s2,e2) then return true else return false
+bool timeIntersect(TSKEY s1, TSKEY e1, TSKEY s2, TSKEY e2) {
+  // s1,e1 and s2,e2 have 7 scenarios, 5 is intersection, 2 is no intersection, so we pick up 2.
+  if(e2 < s1 || s2 > e1)
+    return false;
+  else
+    return true;
+}
\ No newline at end of file

tests/pytest/fulltest.sh

@@ -286,6 +286,7 @@ python3 ./test.py -f query/queryCnameDisplay.py
 python3 test.py -f query/nestedQuery/queryWithSpread.py
 python3 ./test.py -f query/bug6586.py
 # python3 ./test.py -f query/bug5903.py
+python3 ./test.py -f query/queryLimit.py
 
 #stream
 python3 ./test.py -f stream/metric_1.py

tests/pytest/query/queryLimit.py

+###################################################################
+#           Copyright (c) 2016 by TAOS Technologies, Inc.
+#                     All rights reserved.
+#
+#  This file is proprietary and confidential to TAOS Technologies.
+#  No part of this file may be reproduced, stored, transmitted,
+#  disclosed or used in any form or by any means other than as
+#  expressly provided by the written permission from Jianhui Tao
+#
+###################################################################
+
+# -*- coding: utf-8 -*-
+
+import sys
+
+from numpy.lib.function_base import insert
+import taos
+from util.log import *
+from util.cases import *
+from util.sql import *
+import numpy as np
+
+# constant define
+WAITS = 5 # wait seconds
+
+class TDTestCase:
+    #
+    # --------------- main frame -------------------
+    #
+    
+    def caseDescription(self):
+        '''
+        limit and offset keyword function test cases;
+        case1: limit offset base function test
+        case2: limit offset advance test
+        '''
+        return 
+
+    # init
+    def init(self, conn, logSql):
+        tdLog.debug("start to execute %s" % __file__)
+        tdSql.init(conn.cursor())
+        tdSql.prepare()
+        self.create_tables();
+        self.ts = 1500000000000
+
+
+    # run case  
+    def run(self):
+        # insert data
+        self.insert_data("t1", self.ts, 300*10000, 30000);
+        # test base case
+        self.test_case1()
+        tdLog.debug(" LIMIT test_case1 ............ [OK]")
+        # test advance case
+        self.test_case2()
+        tdLog.debug(" LIMIT test_case2 ............ [OK]")
+
+
+    # stop 
+    def stop(self):
+        tdSql.close()
+        tdLog.success("%s successfully executed" % __file__)
+
+    #
+    # --------------- case  -------------------
+    #
+
+    # create table
+    def create_tables(self):
+        # super table
+        tdSql.execute("create table st(ts timestamp, i1 int) tags(area int)");
+        # child table
+        tdSql.execute("create table t1 using st tags(1)");
+        tdSql.execute("create table t2 using st tags(2)");
+        tdSql.execute("create table t3 using st tags(3)");
+        return 
+
+    # insert data1
+    def insert_data(self, tbname, ts_start, count, batch_num):
+        pre_insert = "insert into %s values"%tbname
+        sql = pre_insert
+        tdLog.debug("doing insert table %s rows=%d ..."%(tbname, count))
+        for i in range(count):
+            sql += " (%d,%d)"%(ts_start + i*1000, i)
+            if i >0 and i%batch_num == 0:
+                tdSql.execute(sql)
+                sql = pre_insert
+        # end sql        
+        if sql != pre_insert:
+            tdSql.execute(sql)
+
+        tdLog.debug("INSERT TABLE DATA ............ [OK]")
+        return
+
+    # test case1 base 
+    def test_case1(self):
+        # 
+        # limit base function
+        #
+        # base no where
+        sql = "select * from t1 limit 10"
+        tdSql.waitedQuery(sql, 10, WAITS)
+        tdSql.checkData(0, 1, 0)
+        tdSql.checkData(9, 1, 9)
+        sql = "select * from t1 order by ts desc limit 10" # desc
+        tdSql.waitedQuery(sql, 10, WAITS)
+        tdSql.checkData(0, 1, 2999999)
+        tdSql.checkData(9, 1, 2999990)
+
+        # have where
+        sql = "select * from t1 where ts>='2017-07-14 10:40:01' and ts<'2017-07-14 10:40:06' limit 10"
+        tdSql.waitedQuery(sql, 5, WAITS)
+        tdSql.checkData(0, 1, 1)
+        tdSql.checkData(4, 1, 5)
+        sql = "select * from t1 where ts>='2017-08-18 03:59:52' and ts<'2017-08-18 03:59:57' order by ts desc limit 10" # desc
+        tdSql.waitedQuery(sql, 5, WAITS)
+        tdSql.checkData(0, 1, 2999996)
+        tdSql.checkData(4, 1, 2999992)
+
+        # 
+        # offset base function
+        #
+        # no where
+        sql = "select * from t1 limit 10 offset 5"
+        tdSql.waitedQuery(sql, 10, WAITS)
+        tdSql.checkData(0, 1, 5)
+        tdSql.checkData(9, 1, 14)
+        sql = "select * from t1 order by ts desc limit 10 offset 5" # desc
+        tdSql.waitedQuery(sql, 10, WAITS)
+        tdSql.checkData(0, 1, 2999994)
+        tdSql.checkData(9, 1, 2999985)
+
+        # have where only ts
+        sql = "select * from t1 where ts>='2017-07-14 10:40:10' and ts<'2017-07-14 10:40:20' limit 10 offset 5"
+        tdSql.waitedQuery(sql, 5, WAITS)
+        tdSql.checkData(0, 1, 15)
+        tdSql.checkData(4, 1, 19)
+        sql = "select * from t1 where ts>='2017-08-18 03:59:52' and ts<'2017-08-18 03:59:57' order by ts desc limit 10 offset 4" # desc
+        tdSql.waitedQuery(sql, 1, WAITS)
+        tdSql.checkData(0, 1, 2999992)
+
+        # have where with other column condition
+        sql = "select * from t1 where i1>=1 and i1<11 limit 10 offset 5"
+        tdSql.waitedQuery(sql, 5, WAITS)
+        tdSql.checkData(0, 1, 6)
+        tdSql.checkData(4, 1, 10)
+        sql = "select * from t1 where i1>=300000 and i1<=500000 order by ts desc limit 10 offset 100000" # desc
+        tdSql.waitedQuery(sql, 10, WAITS)
+        tdSql.checkData(0, 1, 400000)
+        tdSql.checkData(9, 1, 399991)
+
+        # have where with ts and other column condition
+        sql = "select * from t1 where ts>='2017-07-14 10:40:10' and ts<'2017-07-14 10:40:50' and i1>=20 and i1<=25 limit 10 offset 5"
+        tdSql.waitedQuery(sql, 1, WAITS)
+        tdSql.checkData(0, 1, 25)
+
+        return 
+
+    # test advance 
+    def test_case2(self):
+        # 
+        # OFFSET merge file data with memory data
+        #
+        
+        # offset
+        sql = "select * from t1 limit 10 offset 72000"
+        tdSql.waitedQuery(sql, 10, WAITS)
+        tdSql.checkData(0, 1, 72000)
+
+        # each insert one row into NO.0 NO.2 NO.7 blocks
+        sql = "insert into t1 values (%d, 0) (%d, 2) (%d, 7)"%(self.ts+1, self.ts + 2*3300*1000+1, self.ts + 7*3300*1000+1)
+        tdSql.execute(sql)
+        # query result
+        sql = "select * from t1 limit 10 offset 72000"
+        tdSql.waitedQuery(sql, 10, WAITS)
+        tdSql.checkData(0, 1, 72000 - 3)
+        
+        # have where
+        sql = "select * from t1 where ts>='2017-07-14 10:40:10' and ts<'2017-07-22 18:40:10' limit 10 offset 72000"
+        tdSql.waitedQuery(sql, 10, WAITS)
+        tdSql.checkData(0, 1, 72000 - 3 + 10 + 1)
+
+        # have where desc
+        sql = "select * from t1 where ts<'2017-07-14 20:40:00' order by ts desc limit 15 offset 36000"
+        tdSql.waitedQuery(sql, 3, WAITS)
+        tdSql.checkData(0, 1, 1)
+
+
+#
+# add case with filename
+#
+tdCases.addWindows(__file__, TDTestCase())
+tdCases.addLinux(__file__, TDTestCase())
\ No newline at end of file