From 6b8b293c44b1b33d0ff7e8894693f20bdbfd17b9 Mon Sep 17 00:00:00 2001
From: Haojun Liao <hjliao@taosdata.com>
Date: Fri, 25 Dec 2020 16:43:47 +0800
Subject: [PATCH] [TD-2512]

---
 src/tsdb/src/tsdbRead.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/src/tsdb/src/tsdbRead.c b/src/tsdb/src/tsdbRead.c
index ed0ad76b1e..7e2e135c4b 100644
--- a/src/tsdb/src/tsdbRead.c
+++ b/src/tsdb/src/tsdbRead.c
@@ -111,7 +111,6 @@ 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;
@@ -136,7 +135,7 @@ typedef struct STableGroupSupporter {
 } STableGroupSupporter;
 
 static STimeWindow updateLastrowForEachGroup(STableGroupInfo *groupList);
-static int32_t extractCachedLastRow(STsdbQueryHandle* pQueryHandle, STableGroupInfo *groupList);
+static int32_t checkForCachedLastRow(STsdbQueryHandle* pQueryHandle, STableGroupInfo *groupList);
 static int32_t tsdbGetCachedLastRow(STable* pTable, SDataRow* pRes, TSKEY* lastKey);
 
 static void    changeQueryHandleForInterpQuery(TsdbQueryHandleT pHandle);
@@ -382,13 +381,14 @@ TsdbQueryHandleT tsdbQueryLastRow(TSDB_REPO_T *tsdb, STsdbQueryCond *pCond, STab
   }
 
   STsdbQueryHandle *pQueryHandle = (STsdbQueryHandle*) tsdbQueryTables(tsdb, pCond, groupList, qinfo, pMemRef);
-  int32_t code = extractCachedLastRow(pQueryHandle, groupList);
+  int32_t code = checkForCachedLastRow(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);
+  pQueryHandle->type = TSDB_QUERY_TYPE_LAST;
   return pQueryHandle;
 }
 
@@ -2155,15 +2155,15 @@ bool tsdbNextDataBlock(TsdbQueryHandleT* pHandle) {
     return ret;
   } 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.
-    int32_t numOfCols = (int32_t)(QH_GET_NUM_OF_COLS(pQueryHandle));
+    // here note that the pQueryHandle->window must be the TS_INITIALIZER
+    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) {
+    if (++pQueryHandle->activeIndex < numOfTables) {
       STableCheckInfo* pCheckInfo = taosArrayGet(pQueryHandle->pTableCheckInfo, pQueryHandle->activeIndex);
       int32_t ret = tsdbGetCachedLastRow(pCheckInfo->pTableObj, &pRow, &key);
       if (ret != TSDB_CODE_SUCCESS) {
@@ -2179,8 +2179,8 @@ bool tsdbNextDataBlock(TsdbQueryHandleT* pHandle) {
       cur->rows     = 1;  // only one row
       cur->lastKey  = key + step;
       cur->mixBlock = true;
-
-      pQueryHandle->activeIndex += 1;
+      cur->win.skey = key;
+      cur->win.ekey = key;
 
       return true;
     }
@@ -2239,7 +2239,7 @@ int32_t tsdbGetCachedLastRow(STable* pTable, SDataRow* pRes, TSKEY* lastKey) {
   return TSDB_CODE_SUCCESS;
 }
 
-int32_t extractCachedLastRow(STsdbQueryHandle* pQueryHandle, STableGroupInfo *groupList) {
+int32_t checkForCachedLastRow(STsdbQueryHandle* pQueryHandle, STableGroupInfo *groupList) {
   assert(pQueryHandle != NULL && groupList != NULL);
 
   SDataRow pRow = NULL;
@@ -2257,6 +2257,13 @@ int32_t extractCachedLastRow(STsdbQueryHandle* pQueryHandle, STableGroupInfo *gr
     pQueryHandle->cachelastrow = (pRow != NULL);
   }
 
+  // update the tsdb query time range
+  if (pQueryHandle->cachelastrow) {
+    pQueryHandle->window      = TSWINDOW_INITIALIZER;
+    pQueryHandle->checkFiles  = false;
+    pQueryHandle->activeIndex = -1;  // start from -1
+  }
+
   tfree(pRow);
   return code;
 }
-- 
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