From b77b767a02b6f461b3352834763639e5683b5a92 Mon Sep 17 00:00:00 2001
From: Haojun Liao <hjliao@taosdata.com>
Date: Thu, 3 Sep 2020 13:53:09 +0800
Subject: [PATCH] [td-1317]

---
 src/query/src/qExecutor.c                     | 28 +++++++++----------
 src/tsdb/src/tsdbRead.c                       |  9 ++++--
 tests/script/general/parser/lastrow_query.sim |  7 ++++-
 3 files changed, 27 insertions(+), 17 deletions(-)

diff --git a/src/query/src/qExecutor.c b/src/query/src/qExecutor.c
index 41daed087c..df4bb009bc 100644
--- a/src/query/src/qExecutor.c
+++ b/src/query/src/qExecutor.c
@@ -1951,36 +1951,36 @@ static void changeExecuteScanOrder(SQInfo *pQInfo, SQueryTableMsg* pQueryMsg, bo
 
   // todo handle the case the the order irrelevant query type mixed up with order critical query type
   // descending order query for last_row query
-  if (isFirstLastRowQuery(pQuery)) {
+  if (isFirstLastRowQuery(pQuery) && !QUERY_IS_ASC_QUERY(pQuery)) {
     qDebug("QInfo:%p scan order changed for last_row query, old:%d, new:%d", GET_QINFO_ADDR(pQuery),
            pQuery->order.order, TSDB_ORDER_ASC);
 
+    SWAP(pQuery->window.skey, pQuery->window.ekey, TSKEY);
     pQuery->order.order = TSDB_ORDER_ASC;
-    if (pQuery->window.skey > pQuery->window.ekey) {
-      SWAP(pQuery->window.skey, pQuery->window.ekey, TSKEY);
-    }
+    assert (pQuery->window.skey <= pQuery->window.ekey);
 
+    doExchangeTimeWindow(pQInfo, &pQuery->window);
     return;
   }
 
-  if (isGroupbyNormalCol(pQuery->pGroupbyExpr) && pQuery->order.order == TSDB_ORDER_DESC) {
+  if (isGroupbyNormalCol(pQuery->pGroupbyExpr) && !QUERY_IS_ASC_QUERY(pQuery)) {
     pQuery->order.order = TSDB_ORDER_ASC;
-    if (pQuery->window.skey > pQuery->window.ekey) {
-      SWAP(pQuery->window.skey, pQuery->window.ekey, TSKEY);
-    }
+    SWAP(pQuery->window.skey, pQuery->window.ekey, TSKEY);
+    assert (pQuery->window.skey <= pQuery->window.ekey);
 
     doExchangeTimeWindow(pQInfo, &pQuery->window);
     return;
   }
 
-  if (isPointInterpoQuery(pQuery) && pQuery->intervalTime == 0) {
-    if (!QUERY_IS_ASC_QUERY(pQuery)) {
-      qDebug(msg, GET_QINFO_ADDR(pQuery), "interp", pQuery->order.order, TSDB_ORDER_ASC, pQuery->window.skey,
-             pQuery->window.ekey, pQuery->window.ekey, pQuery->window.skey);
-      SWAP(pQuery->window.skey, pQuery->window.ekey, TSKEY);
-    }
+  if (isPointInterpoQuery(pQuery) && (pQuery->intervalTime == 0) && !QUERY_IS_ASC_QUERY(pQuery)) {
+    qDebug(msg, GET_QINFO_ADDR(pQuery), "interp", pQuery->order.order, TSDB_ORDER_ASC, pQuery->window.skey,
+           pQuery->window.ekey, pQuery->window.ekey, pQuery->window.skey);
+    SWAP(pQuery->window.skey, pQuery->window.ekey, TSKEY);
 
     pQuery->order.order = TSDB_ORDER_ASC;
+
+    assert (pQuery->window.skey <= pQuery->window.ekey);
+    doExchangeTimeWindow(pQInfo, &pQuery->window);
     return;
   }
 
diff --git a/src/tsdb/src/tsdbRead.c b/src/tsdb/src/tsdbRead.c
index f8ff25ddab..d8f8d8f9f1 100644
--- a/src/tsdb/src/tsdbRead.c
+++ b/src/tsdb/src/tsdbRead.c
@@ -295,9 +295,10 @@ out_of_memory:
 }
 
 TsdbQueryHandleT tsdbQueryLastRow(TSDB_REPO_T *tsdb, STsdbQueryCond *pCond, STableGroupInfo *groupList, void* qinfo) {
-  pCond->order = TSDB_ORDER_ASC;
   pCond->twindow = changeTableGroupByLastrow(groupList);
   STsdbQueryHandle *pQueryHandle = (STsdbQueryHandle*) tsdbQueryTables(tsdb, pCond, groupList, qinfo);
+
+  assert(pCond->order == TSDB_ORDER_ASC && pCond->twindow.skey <= pCond->twindow.ekey);
   return pQueryHandle;
 }
 
@@ -1982,7 +1983,6 @@ STimeWindow changeTableGroupByLastrow(STableGroupInfo *groupList) {
   STimeWindow window = {INT64_MAX, INT64_MIN};
 
   // NOTE: starts from the buffer in case of descending timestamp order check data blocks
-  // todo consider the query time window, current last_row does not apply the query time window
   size_t numOfGroups = taosArrayGetSize(groupList->pGroupList);
   for(int32_t j = 0; j < numOfGroups; ++j) {
     SArray* pGroup = taosArrayGetP(groupList->pGroupList, j);
@@ -2019,6 +2019,11 @@ STimeWindow changeTableGroupByLastrow(STableGroupInfo *groupList) {
     }
   }
 
+  // window does not being updated, so set the original
+  if (window.skey == INT64_MAX && window.ekey == INT64_MIN) {
+    window = TSWINDOW_INITIALIZER;
+  }
+
   return window;
 }
 
diff --git a/tests/script/general/parser/lastrow_query.sim b/tests/script/general/parser/lastrow_query.sim
index 1459b7b470..ef00af3210 100644
--- a/tests/script/general/parser/lastrow_query.sim
+++ b/tests/script/general/parser/lastrow_query.sim
@@ -153,4 +153,9 @@ if $rows != 46 then
   return -1
 endi
 
-
+print ========>td-1317, empty table last_row query crashed
+sql create table t1(ts timestamp, k int)
+sql select last_row(*) from t1
+if $rows != 0 then
+  return -1
+endi
-- 
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