[TD-2512]

src/query/src/qExecutor.c

@@ -4662,7 +4662,6 @@ static int32_t setupQueryHandle(void* tsdb, SQInfo* pQInfo, bool isSTableQuery)
 
     // update the query time window
     pQuery->window = cond.twindow;
-
     if (pQInfo->tableGroupInfo.numOfTables == 0) {
       pQInfo->tableqinfoGroupInfo.numOfTables = 0;
     } else {

src/tsdb/src/tsdbRead.c

@@ -111,6 +111,7 @@ typedef struct STsdbQueryHandle {
   int32_t        activeIndex;
   bool           checkFiles;       // check file stage
   bool           cachelastrow;     // check if last row cached
+  SArray*        cachedRows;       // cached last rows
   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;
@@ -135,7 +136,8 @@ typedef struct STableGroupSupporter {
 } STableGroupSupporter;
 
 static STimeWindow updateLastrowForEachGroup(STableGroupInfo *groupList);
-static void checkCachedLastRow(STsdbQueryHandle* pQueryHandle, STableGroupInfo *groupList);
+static int32_t extractCachedLastRow(STsdbQueryHandle* pQueryHandle, STableGroupInfo *groupList);
+static int32_t tsdbGetCachedLastRow(STable* pTable, SDataRow* pRes, TSKEY* lastKey);
 
 static void    changeQueryHandleForInterpQuery(TsdbQueryHandleT pHandle);
 static void    doMergeTwoLevelData(STsdbQueryHandle* pQueryHandle, STableCheckInfo* pCheckInfo, SCompBlock* pBlock);
@@ -380,7 +382,11 @@ TsdbQueryHandleT tsdbQueryLastRow(TSDB_REPO_T *tsdb, STsdbQueryCond *pCond, STab
   }
 
   STsdbQueryHandle *pQueryHandle = (STsdbQueryHandle*) tsdbQueryTables(tsdb, pCond, groupList, qinfo, pMemRef);
-  checkCachedLastRow(pQueryHandle, groupList);
+  int32_t code = extractCachedLastRow(pQueryHandle, groupList);
+  if (code != TSDB_CODE_SUCCESS) { // set the numOfTables to be 0
+    terrno = code;
+    return NULL;
+  }
 
   assert(pCond->order == TSDB_ORDER_ASC && pCond->twindow.skey <= pCond->twindow.ekey);
   return pQueryHandle;
@@ -2150,7 +2156,36 @@ bool tsdbNextDataBlock(TsdbQueryHandleT* pHandle) {
   } else if (pQueryHandle->type == TSDB_QUERY_TYPE_LAST && pQueryHandle->cachelastrow) {
     // the last row is cached in buffer, return it directly.
     // here note that the pQueryHandle->window may need to be updated.
-    assert(0);
+    int32_t numOfCols = (int32_t)(QH_GET_NUM_OF_COLS(pQueryHandle));
+    SQueryFilePos* cur = &pQueryHandle->cur;
+
+    SDataRow pRow = NULL;
+    TSKEY    key  = TSKEY_INITIAL_VAL;
+    int32_t  step = ASCENDING_TRAVERSE(pQueryHandle->order)? 1:-1;
+
+    while (pQueryHandle->activeIndex < numOfTables) {
+      STableCheckInfo* pCheckInfo = taosArrayGet(pQueryHandle->pTableCheckInfo, pQueryHandle->activeIndex);
+      int32_t ret = tsdbGetCachedLastRow(pCheckInfo->pTableObj, &pRow, &key);
+      if (ret != TSDB_CODE_SUCCESS) {
+        return false;
+      }
+
+      copyOneRowFromMem(pQueryHandle, pQueryHandle->outputCapacity, 0, pRow, numOfCols, pCheckInfo->pTableObj);
+      tfree(pRow);
+
+      // update the last key value
+      pCheckInfo->lastKey = key + step;
+
+      cur->rows     = 1;  // only one row
+      cur->lastKey  = key + step;
+      cur->mixBlock = true;
+
+      pQueryHandle->activeIndex += 1;
+
+      return true;
+    }
+
+    return false;
   }
 
   if (pQueryHandle->checkFiles) {
@@ -2188,33 +2223,42 @@ bool tsdbNextDataBlock(TsdbQueryHandleT* pHandle) {
  * 2. has data but not loaded, just return lastKey but not set pRes
  * 3. has data and loaded, return lastKey and set pRes
  */
-TSKEY tsdbGetCachedLastRow(STable* pTable, void** pRes) {
-  TSKEY lastKey;
-
+int32_t tsdbGetCachedLastRow(STable* pTable, SDataRow* pRes, TSKEY* lastKey) {
   TSDB_RLOCK_TABLE(pTable);
-  lastKey = pTable->lastKey;
+  *lastKey = pTable->lastKey;
 
-  if (lastKey != TSKEY_INITIAL_VAL && pTable->lastRow) {
+  if ((*lastKey) != TSKEY_INITIAL_VAL && pTable->lastRow) {
     *pRes = tdDataRowDup(pTable->lastRow);
     if (*pRes == NULL) {
-      // TODO: handle error
+      TSDB_RUNLOCK_TABLE(pTable);
+      return TSDB_CODE_TDB_OUT_OF_MEMORY;
     }
   }
+
   TSDB_RUNLOCK_TABLE(pTable);
-  return lastKey;
+  return TSDB_CODE_SUCCESS;
 }
 
-void checkCachedLastRow(STsdbQueryHandle* pQueryHandle, STableGroupInfo *groupList) {
+int32_t extractCachedLastRow(STsdbQueryHandle* pQueryHandle, STableGroupInfo *groupList) {
   assert(pQueryHandle != NULL && groupList != NULL);
 
-  void* pRes = NULL;
-  SArray* group = taosArrayGet(groupList->pGroupList, 0);
+  SDataRow pRow = NULL;
+  TSKEY    key = TSKEY_INITIAL_VAL;
+
+  SArray* group = taosArrayGetP(groupList->pGroupList, 0);
   assert(group != NULL);
 
   STableKeyInfo* pInfo = (STableKeyInfo*)taosArrayGet(group, 0);
 
-  int32_t ret = tsdbGetCachedLastRow(pInfo->pTable, &pRes);
-  pQueryHandle->cachelastrow = (ret == TSDB_CODE_SUCCESS);
+  int32_t code = tsdbGetCachedLastRow(pInfo->pTable, &pRow, &key);
+  if (code != TSDB_CODE_SUCCESS) {
+    pQueryHandle->cachelastrow = false;
+  } else {
+    pQueryHandle->cachelastrow = (pRow != NULL);
+  }
+
+  tfree(pRow);
+  return code;
 }
 
 STimeWindow updateLastrowForEachGroup(STableGroupInfo *groupList) {