offset skip block is ok except think about mem delay data

src/inc/tsdb.h

@@ -172,6 +172,7 @@ 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

@@ -228,6 +228,7 @@ 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

@@ -4922,6 +4922,7 @@ static void doTableQueryInfoTimeWindowCheck(SQueryAttr* pQueryAttr, STableQueryI
   }
 }
 
+
 STsdbQueryCond createTsdbQueryCond(SQueryAttr* pQueryAttr, STimeWindow* win) {
   STsdbQueryCond cond = {
       .colList   = pQueryAttr->tableCols,
@@ -4931,6 +4932,12 @@ 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;
 }
@@ -5851,19 +5858,38 @@ 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);
-      pBlock->info.rows = remain;
+      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;
@@ -8470,6 +8496,18 @@ SQInfo* createQInfoImpl(SQueryTableMsg* pQueryMsg, SGroupbyExpr* pGroupbyExpr, S
     goto _cleanup;
   }
 
+  // calc skipOffset 
+  if(pQueryMsg->offset > 0 && TSDB_QUERY_HAS_TYPE(pQueryMsg->queryType, TSDB_QUERY_TYPE_PROJECTION_QUERY)) {
+     pQueryAttr->skipOffset = true;
+     for (int32_t i = 0; i < pQueryAttr->numOfCols; ++i) {
+       if (pQueryAttr->tableCols[i].flist.numOfFilters > 0 
+        && pQueryAttr->tableCols[i].colId != PRIMARYKEY_TIMESTAMP_COL_INDEX) {
+         pQueryAttr->skipOffset = false;  
+         break;    
+       }
+     }
+  }
+
   if (pSecExprs != NULL) {
     int32_t resultRowSize = 0;
 

src/tsdb/src/tsdbRead.c

@@ -37,6 +37,9 @@
                     .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,
@@ -115,6 +118,9 @@ 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 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;
@@ -409,6 +415,9 @@ 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;
@@ -525,6 +534,9 @@ 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;
@@ -1033,6 +1045,51 @@ static int32_t binarySearchForBlock(SBlock* pBlock, int32_t numOfBlocks, TSKEY s
   return midSlot;
 }
 
+// skip blocks . return value is skip blocks number, skip rows reduce from *pOffset
+static int32_t offsetSkipBlock(STsdbQueryHandle* q, SBlockInfo* pBlockInfo, uint32_t numBlocks, int64_t s, int64_t e) {
+  int32_t num = 0;
+  SBlock* blocks = pBlockInfo->blocks;
+
+  // asc
+  if(ASCENDING_TRAVERSE(q->order)) {
+    for(int32_t i = 0; i < numBlocks; i++) {
+      SBlock* pBlock = &blocks[i];
+      if(i == 0 && pBlock->keyFirst != s) { 
+        //first block only keyFirst == s can skip
+        q->frows += pBlock->numOfRows;
+        continue;
+      } else {
+        // skip to read
+        if(q->srows + q->frows + pBlock->numOfRows <= q->offset) {
+          q->srows += pBlock->numOfRows;
+          num ++;
+        } else {
+          break;
+        }
+      }
+    }
+  } else { // des
+    for(int32_t i = numBlocks - 1; i >= 0; i--) {
+      SBlock* pBlock = &blocks[i];
+      if(i == numBlocks - 1 && pBlock->keyLast != e) { 
+        //first block only keyFirst == s can skipƒ
+        q->frows += pBlock->numOfRows;
+        continue;
+      } else {
+        // skip to read
+        if(q->srows + q->frows + pBlock->numOfRows <= q->offset) {
+          q->srows += pBlock->numOfRows;
+          num ++;
+        } else {
+          break;
+        }
+      }
+    }    
+  }
+
+  return num;
+}
+
 static int32_t loadBlockInfo(STsdbQueryHandle * pQueryHandle, int32_t index, int32_t* numOfBlocks) {
   int32_t code = 0;
 
@@ -1083,22 +1140,39 @@ static int32_t loadBlockInfo(STsdbQueryHandle * pQueryHandle, int32_t index, int
 
   // 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;
   }
 
+  int32_t end = start;
   // todo speedup the procedure of located end block
   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;
+  if(pQueryHandle->offset > 0) {
+     nSkip = offsetSkipBlock(pQueryHandle, pCompInfo, compIndex->numOfBlocks, s, e);
+  }
 
-  if (start > 0) {
+  pCheckInfo->numOfBlocks = (end - start) - nSkip;
+  if(pCheckInfo->numOfBlocks > 0) {
+    if(nSkip > 0) {
+      if(ASCENDING_TRAVERSE(pQueryHandle->order)) {
+        if(start > 0)
+          memmove(pCompInfo->blocks, &pCompInfo->blocks[start], 1 * sizeof(SBlock));
+        if(pCheckInfo->numOfBlocks > 1)
+          memmove(pCompInfo->blocks + 1, &pCompInfo->blocks[start + nSkip + 1], (pCheckInfo->numOfBlocks - 1) * sizeof(SBlock));
+      } else {
+        if(start > 0 && pCheckInfo->numOfBlocks > 1)
+          memmove(pCompInfo->blocks, &pCompInfo->blocks[start], (pCheckInfo->numOfBlocks - 1) * sizeof(SBlock));
+        memmove(pCompInfo->blocks + (pCheckInfo->numOfBlocks - 1), &pCompInfo->blocks[end - 1], 1 * sizeof(SBlock)); 
+      }
+    } else if(start > 0) {
       memmove(pCompInfo->blocks, &pCompInfo->blocks[start], pCheckInfo->numOfBlocks * sizeof(SBlock));
     }
+  }
 
   (*numOfBlocks) += pCheckInfo->numOfBlocks;
   return 0;
@@ -4208,3 +4282,12 @@ void getTableListfromSkipList(tExprNode *pExpr, SSkipList *pSkipList, SArray *re
   //apply the hierarchical filter expression to every node in skiplist to find the qualified nodes
   applyFilterToSkipListNode(pSkipList, pExpr, result, param);
 }
+
+// obtain queryHandle attribute
+int64_t tsdbSkipOffset(TsdbQueryHandleT queryHandle) {
+  STsdbQueryHandle* pQueryHandle = (STsdbQueryHandle*)queryHandle;
+  if (pQueryHandle) {
+    return pQueryHandle->srows;
+  }
+  return 0;
+}
\ No newline at end of file