[TS-2016](query,insert,other,connector,tools):fix app error of select from...

[TS-2016](query,insert,other,connector,tools):fix app error of select from (select * from empty_stable) by set subquery command to retrieve empty results

src/client/src/tscUtil.c

@@ -4300,7 +4300,11 @@ void executeQuery(SSqlObj* pSql, SQueryInfo* pQueryInfo) {
       pSql->pSubs[i] = pNew;
 
       SSqlCmd* pCmd = &pNew->cmd;
-      pCmd->command = TSDB_SQL_SELECT;
+      if (pSub->command == TSDB_SQL_RETRIEVE_EMPTY_RESULT) {
+        pCmd->command = TSDB_SQL_RETRIEVE_EMPTY_RESULT;
+      } else {
+        pCmd->command = TSDB_SQL_SELECT;
+      }
       if ((code = tscAddQueryInfo(pCmd)) != TSDB_CODE_SUCCESS) {
         goto _error;
       }

tests/develop-test/2-query/ts_2016.py

+###################################################################
+#           Copyright (c) 2021 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 util.log import *
+from util.cases import *
+from util.sql import *
+
+
+class TDTestCase:
+    def caseDescription(self):
+        '''
+        case1<shenglian zhou>: [TS-2016]fix select * from (select * from empty_stable) 
+        ''' 
+        return
+    
+    def init(self, conn, logSql):
+        tdLog.debug("start to execute %s" % __file__)
+        tdSql.init(conn.cursor(), logSql)
+        self._conn = conn
+
+    def run(self):
+        print("running {}".format(__file__))
+        tdSql.execute("drop database if exists td12229")
+        tdSql.execute("create database if not exists td12229")
+        tdSql.execute('use td12229')
+
+        tdSql.execute('create stable st(ts timestamp , value int ) tags (ind int)') 
+        tdSql.execute('insert into tb1 using st tags(1) values(now ,1)') 
+        tdSql.execute('insert into tb1 using st tags(1) values(now+1s ,2)') 
+        tdSql.execute('insert into tb1 using st tags(1) values(now+2s ,3)') 
+        tdSql.execute('create stable ste(ts timestamp , value int ) tags (ind int)') 
+        tdSql.query('select * from st')
+        tdSql.checkRows(3)
+        tdSql.query('select * from (select * from ste)')
+        tdSql.checkRows(0)
+        tdSql.query('select * from st union all select * from ste')
+        tdSql.checkRows(3)
+        tdSql.query('select * from ste union all select * from st')
+        tdSql.checkRows(3)
+        tdSql.query('select elapsed(ts) from ste group by tbname union all select elapsed(ts) from st group by tbname;')
+        tdSql.checkRows(1)
+        tdSql.query('select elapsed(ts) from st group by tbname union all select elapsed(ts) from ste group by tbname;')
+        tdSql.checkRows(1)
+        tdSql.execute('drop database td12229')
+    def stop(self):
+        tdSql.close()
+        tdLog.success("%s successfully executed" % __file__)
+
+
+tdCases.addWindows(__file__, TDTestCase())
+tdCases.addLinux(__file__, TDTestCase())

tests/develop-test/fulltest-query.sh

 python3 ./test.py -f 2-query/ts_hidden_column.py
 python3 ./test.py -f 2-query/union-order.py
 python3 ./test.py -f 2-query/session_two_stage.py
+python3 ./test.py -f 2-query/ts_2016.py