diff --git a/alert/README.md b/alert/README.md
index 547f3a0381..b8b8c92a27 100644
--- a/alert/README.md
+++ b/alert/README.md
@@ -61,7 +61,7 @@ The use of each configuration item is:
 
 * **port**: This is the `http` service port which enables other application to manage rules by `restful API`.
 * **database**: rules are stored in a `sqlite` database, this is the path of the database file (if the file does not exist, the alert application creates it automatically).
-* **tdengine**: connection string of `TDEngine` server, note the database name should be put in the `sql` field of a rule in most cases, thus it should NOT be included in the string.
+* **tdengine**: connection string of `TDEngine` server (please refer the documentation of GO connector for the detailed format of this string), note the database name should be put in the `sql` field of a rule in most cases, thus it should NOT be included in the string.
 * **log > level**: log level, could be `production` or `debug`.
 * **log > path**: log output file path.
 * **receivers > alertManager**: the alert application pushes alerts to `AlertManager` at this URL.
diff --git a/alert/README_cn.md b/alert/README_cn.md
index 938b23a584..f659e997e3 100644
--- a/alert/README_cn.md
+++ b/alert/README_cn.md
@@ -58,7 +58,7 @@ $ go build
 
 * **port**：报警监测程序支持使用 `restful API` 对规则进行管理，这个参数用于配置 `http` 服务的侦听端口。
 * **database**：报警监测程序将规则保存到了一个 `sqlite` 数据库中，这个参数用于指定数据库文件的路径（不需要提前创建这个文件，如果它不存在，程序会自动创建它）。
-* **tdengine**：`TDEngine` 的连接字符串，一般来说，数据库名应该在报警规则的 `sql` 语句中指定，所以这个字符串中 **不** 应包含数据库名。
+* **tdengine**：`TDEngine` 的连接字符串（这个字符串的详细格式说明请见 GO 连接器的文档），一般来说，数据库名应该在报警规则的 `sql` 语句中指定，所以这个字符串中 **不** 应包含数据库名。
 * **log > level**：日志的记录级别，可选 `production` 或 `debug`。
 * **log > path**：日志文件的路径。
 * **receivers > alertManager**：报警监测程序会将报警推送到 `AlertManager`，在这里指定 `AlertManager` 的接收地址。
diff --git a/alert/app/rule.go b/alert/app/rule.go
index 44596ca26d..236e5bd755 100644
--- a/alert/app/rule.go
+++ b/alert/app/rule.go
@@ -84,6 +84,7 @@ func (alert *Alert) doRefresh(firing bool, rule *Rule) bool {
 
 	case firing && (alert.State == AlertStateWaiting):
 		alert.StartsAt = time.Now()
+		alert.EndsAt = time.Time{}
 		if rule.For.Nanoseconds() > 0 {
 			alert.State = AlertStatePending
 			return false
@@ -95,6 +96,7 @@ func (alert *Alert) doRefresh(firing bool, rule *Rule) bool {
 			return false
 		}
 		alert.StartsAt = alert.StartsAt.Add(rule.For.Duration)
+		alert.EndsAt = time.Time{}
 		alert.State = AlertStateFiring
 
 	case firing && (alert.State == AlertStateFiring):
diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index b55326bbd3..069f7303d6 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -6412,7 +6412,7 @@ int32_t doCheckForQuery(SSqlObj* pSql, SQuerySQL* pQuerySql, int32_t index) {
       return code;
     }
 
-    tVariantListItem* p1 = taosArrayGet(pQuerySql->from, i);
+    tVariantListItem* p1 = taosArrayGet(pQuerySql->from, i + 1);
     if (p1->pVar.nType != TSDB_DATA_TYPE_BINARY) {
       return invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg11);
     }
diff --git a/tests/perftest-scripts/perftest-query.sh b/tests/perftest-scripts/perftest-query.sh
index bb5d9e0a9d..51bb9b36c3 100755
--- a/tests/perftest-scripts/perftest-query.sh
+++ b/tests/perftest-scripts/perftest-query.sh
@@ -1,8 +1,8 @@
 #!/bin/bash
 
 today=`date +"%Y%m%d"`
-WORK_DIR=/home/ubuntu/pxiao/
-PERFORMANCE_TEST_REPORT=$TDENGINE_DIR/tests/performance-test-report-$today.log
+WORK_DIR=/home/ubuntu/pxiao
+PERFORMANCE_TEST_REPORT=$WORK_DIR/TDengine/tests/performance-test-report-$today.log
 
 # Coloured Echoes                                                                                                       #
 function red_echo      { echo -e "\033[31m$@\033[0m";   }                                                               #
@@ -60,11 +60,12 @@ function buildTDengine {
 }
 
 function runQueryPerfTest {
-	nohup $WORK_DIR/TDengine/debug/build/bin/taosd -c /etc/taodperf/ > /dev/null 2>&1 &
+	[ -f $PERFORMANCE_TEST_REPORT ] && rm $PERFORMANCE_TEST_REPORT
+	nohup $WORK_DIR/TDengine/debug/build/bin/taosd -c /etc/taosperf/ > /dev/null 2>&1 &
 	echoInfo "Run Performance Test"
 	cd $WORK_DIR/TDengine/tests/pytest
 	
-	python3 query/queryPerformance.py | tee -a $PERFORMANCE_TEST_REPORT
+	python3 query/queryPerformance.py 0 | tee -a $PERFORMANCE_TEST_REPORT
 }
 
 
@@ -77,9 +78,9 @@ function sendReport {
 
 	sed -i 's/\x1b\[[0-9;]*m//g' $PERFORMANCE_TEST_REPORT
 	BODY_CONTENT=`cat $PERFORMANCE_TEST_REPORT`
-	echo -e "to: ${receiver}\nsubject: Query Performace Report ${today}, commit ID: ${LOCAL_COMMIT}\n\n${today}:\n${BODY_CONTENT}" | \
+	echo -e "From: <support@taosdata.com>\nto: ${receiver}\nsubject: Query Performace Report ${today}, commit ID: ${LOCAL_COMMIT}\n\n${today}:\n${BODY_CONTENT}" | \
 	(cat - && uuencode $PERFORMANCE_TEST_REPORT performance-test-report-$today.log) | \
-	ssmtp "${receiver}" && echo "Report Sent!"
+	/usr/sbin/ssmtp "${receiver}" && echo "Report Sent!"
 }
 
 
diff --git a/tests/pytest/fulltest.sh b/tests/pytest/fulltest.sh
index 3a9aa00617..525fbad6c1 100755
--- a/tests/pytest/fulltest.sh
+++ b/tests/pytest/fulltest.sh
@@ -202,6 +202,7 @@ python3 queryCount.py
 python3 ./test.py -f query/queryGroupbyWithInterval.py
 python3 client/twoClients.py
 python3 test.py -f query/queryInterval.py
+python3 test.py -f query/queryFillTest.py
 
 # tools
 python3 test.py -f tools/taosdemo.py
diff --git a/tests/pytest/query/queryFillTest.py b/tests/pytest/query/queryFillTest.py
new file mode 100644
index 0000000000..d4dfeab13d
--- /dev/null
+++ b/tests/pytest/query/queryFillTest.py
@@ -0,0 +1,70 @@
+###################################################################
+#           Copyright (c) 2016 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
+import taos
+from util.log import tdLog
+from util.cases import tdCases
+from util.sql import tdSql
+
+
+class TDTestCase:
+    def init(self, conn, logSql):
+        tdLog.debug("start to execute %s" % __file__)
+        tdSql.init(conn.cursor(), logSql)
+
+        self.ts = 1537146000000
+
+    def run(self):
+        tdSql.prepare()
+
+        print("==============step1")
+        tdSql.execute(
+            "create table if not exists stb (ts timestamp, col1 int, col2 int, col3 int) tags(loc nchar(20), id int)")
+        tdSql.execute(
+            "insert into tb0 using stb tags('beijing', 1) values(%s, 1, 1, 1)(%s, 2, 2, 2)(%s, 3, 3, 3)(%s, 4, 4, 4)" % (self.ts, self.ts + 1000000, self.ts + 2000000, self.ts + 3000000))
+        tdSql.execute(
+            "insert into tb1 using stb tags('beijing', 2) values(%s, 1, 1, 1)(%s, 2, 2, 2)(%s, 3, 3, 3)(%s, 4, 4, 4)" % (self.ts + 4000000, self.ts + 5000000, self.ts + 6000000, self.ts + 7000000))
+        tdSql.execute(
+            "insert into tb2 using stb tags('shanghai', 1) values(%s, 1, 1, 1)(%s, 2, 2, 2)(%s, 3, 3, 3)(%s, 4, 4, 4)" % (self.ts + 8000000, self.ts + 9000000, self.ts + 10000000, self.ts + 11000000))
+        tdSql.execute(
+            "insert into tb3 using stb tags('shanghai', 2) values(%s, 1, 1, 1)(%s, 2, 2, 2)(%s, 3, 3, 3)(%s, 4, 4, 4)" % (self.ts + 12000000, self.ts + 13000000, self.ts + 14000000, self.ts + 15000000))
+        tdSql.execute(
+            "insert into tb4 using stb tags('shanghai', 3) values(%s, null, null, null)(%s, null, null, null)(%s, null, null, null)(%s, null, null, null)" % (self.ts + 16000000, self.ts + 17000000, self.ts + 18000000, self.ts + 19000000))
+        
+        tdSql.query("select first(col1) - avg(col1) from stb where ts > '2018-09-17 08:00:00.000' and ts < '2018-09-17 14:16:41.000' interval(1h)")
+        tdSql.checkRows(5)
+        tdSql.checkData(0, 1, -1.5)
+        tdSql.checkData(1, 1, -1.5)
+        tdSql.checkData(2, 1, -1.0)
+        tdSql.checkData(3, 1, 1.5)
+        tdSql.checkData(4, 1, 0)
+
+        tdSql.query("select first(col1) - avg(col1) from stb where ts > '2018-09-17 08:00:00.000' and ts < '2018-09-17 14:16:41.000' interval(1h) fill(null)")
+        tdSql.checkRows(7)
+        tdSql.checkData(0, 1, None)
+        tdSql.checkData(6, 1, None)       
+
+        tdSql.query("select max(col1) - min(col1) from stb where ts > '2018-09-17 08:00:00.000' and ts < '2018-09-17 14:16:41.000' and id = 1 group by loc, id")
+        tdSql.checkRows(2)
+
+        tdSql.query("select spread(col1) from stb where ts > '2018-09-17 08:00:00.000' and ts < '2018-09-17 14:16:41.000' and id = 1 group by loc, id")
+        tdSql.checkRows(2)
+        
+    def stop(self):
+        tdSql.close()
+        tdLog.success("%s successfully executed" % __file__)
+
+
+tdCases.addWindows(__file__, TDTestCase())
+tdCases.addLinux(__file__, TDTestCase())
\ No newline at end of file
diff --git a/tests/pytest/query/queryPerformance.py b/tests/pytest/query/queryPerformance.py
index e09900acc4..72af38450c 100644
--- a/tests/pytest/query/queryPerformance.py
+++ b/tests/pytest/query/queryPerformance.py
@@ -23,7 +23,7 @@ class taosdemoQueryPerformace:
         self.host = "127.0.0.1"
         self.user = "root"
         self.password = "taosdata"
-        self.config = "/etc/taos"
+        self.config = "/etc/taosperf"
         self.conn = taos.connect(
             self.host,
             self.user,