`select colum1,AVG(colum2) ...`, dble hangs

[actiontech-bot]

Raised by: @sevenFH

mysql> select * from mytest_test1;
+-----+-----------+----------+-------------+--------+
| ID  | FirstName | LastName | Department  | Salary |
+-----+-----------+----------+-------------+--------+
| 202 | Jozzh     | Lnanyo   | Finance     |  45800 |
| 206 | Dnnaao    | Errllov  | Development |  55000 |
| 204 | Gecrrcc   | Srlkrt   | Finance     |  62000 |
| 201 | Mazojys   | Fxoj     | Finance     |   7800 |
| 203 | Syllauu   | Dfaafk   | Finance     |  57000 |
| 207 | Tyoysww   | Osk      | Development |  49000 |
| 205 | Jssme     | Bdnaa    | Development |  75000 |
+-----+-----------+----------+-------------+--------+
7 rows in set (0.14 sec)

mysql> select department,sum(salary) from mytest_test1 group by department;
+-------------+--------------------------+
| department  | SUM(mytest_test1.salary) |
+-------------+--------------------------+
| Development | 179000                   |
| Finance     | 172600                   |
+-------------+--------------------------+
2 rows in set (0.12 sec)

mysql> select department,avg(salary) from mytest_test1 group by department;
//no response and the connection is not released 

my.log

2017-08-31 15:08:35.157  INFO [BusinessExecutor6] (io.mycat.backend.mysql.nio.handler.query.impl.BaseSelectHandler.execute(BaseSelectHandler.java:63)) - MySQLConnection [id=110, lastTime=1504163315157, user=test, schema=db2, old shema=db2, borrowed=true, fromSlaveDB=false, threadId=2745, charset=utf8, txIsolation=-1, autocommit=true, attachment=null, respHandler=io.mycat.backend.mysql.nio.handler.query.impl.BaseSelectHandler@1b8b7855, host=10.186.23.67, port=3306, statusSync=null, writeQueue=0, modifiedSQLExecuted=false] send sql:select `mytest_test1`.`department`,SUM(mytest_test1.salary) as `_$SUM$_rpda_0`,COUNT(mytest_test1.salary) as `_$COUNT$_rpda_0` from  `mytest_test1` GROUP BY `mytest_test1`.`department` ASC
2017-08-31 15:08:35.157  INFO [BusinessExecutor6] (io.mycat.backend.mysql.nio.handler.builder.HandlerBuilder.build(HandlerBuilder.java:65)) - HandlerBuilder.build cost:1595202
2017-08-31 15:08:35.158  INFO [complexQueryExecutor5] (io.mycat.backend.mysql.nio.handler.query.impl.MultiNodeMergeHandler.fieldEofResponse(MultiNodeMergeHandler.java:94)) - MySQLConnection [id=58, lastTime=1504163315153, user=test, schema=db2, old shema=db2, borrowed=true, fromSlaveDB=false, threadId=4434, charset=utf8, txIsolation=3, autocommit=true, attachment=null, respHandler=io.mycat.backend.mysql.nio.handler.query.impl.BaseSelectHandler@300d77eb, host=10.186.23.11, port=3306, statusSync=io.mycat.backend.mysql.nio.MySQLConnection$StatusSync@4f2fcdef, writeQueue=0, modifiedSQLExecuted=false]'s field is reached.
2017-08-31 15:08:35.159  INFO [complexQueryExecutor4] (io.mycat.backend.mysql.nio.handler.query.impl.MultiNodeMergeHandler.fieldEofResponse(MultiNodeMergeHandler.java:94)) - MySQLConnection [id=110, lastTime=1504163315153, user=test, schema=db2, old shema=db2, borrowed=true, fromSlaveDB=false, threadId=2745, charset=utf8, txIsolation=3, autocommit=true, attachment=null, respHandler=io.mycat.backend.mysql.nio.handler.query.impl.BaseSelectHandler@1b8b7855, host=10.186.23.67, port=3306, statusSync=io.mycat.backend.mysql.nio.MySQLConnection$StatusSync@7e611102, writeQueue=0, modifiedSQLExecuted=false]'s field is reached.
2017-08-31 15:08:35.159  INFO [complexQueryExecutor4] (io.mycat.backend.mysql.nio.handler.query.impl.MultiNodeMergeHandler.rowEofResponse(MultiNodeMergeHandler.java:141)) - MySQLConnection [id=110, lastTime=1504163315153, user=test, schema=db2, old shema=db2, borrowed=true, fromSlaveDB=false, threadId=2745, charset=utf8, txIsolation=3, autocommit=true, attachment=null, respHandler=io.mycat.backend.mysql.nio.handler.query.impl.BaseSelectHandler@1b8b7855, host=10.186.23.67, port=3306, statusSync=io.mycat.backend.mysql.nio.MySQLConnection$StatusSync@7e611102, writeQueue=0, modifiedSQLExecuted=false] 's rowEof is reached.
2017-08-31 15:08:35.159  WARN [complexQueryExecutor5] (io.mycat.backend.mysql.nio.MySQLConnectionHandler.handleDataError(MySQLConnectionHandler.java:231)) - MySQLConnection [id=58, lastTime=1504163315153, user=test, schema=db2, old shema=db2, borrowed=true, fromSlaveDB=false, threadId=4434, charset=utf8, txIsolation=3, autocommit=true, attachment=null, respHandler=io.mycat.backend.mysql.nio.handler.query.impl.BaseSelectHandler@300d77eb, host=10.186.23.11, port=3306, statusSync=io.mycat.backend.mysql.nio.MySQLConnection$StatusSync@4f2fcdef, writeQueue=0, modifiedSQLExecuted=false] handle data error:
java.lang.NullPointerException: null
	at io.mycat.backend.mysql.nio.handler.util.HandlerTool.findField(HandlerTool.java:273) ~[Action_Mycat-2.17.08.0-dev.jar:?]
	at io.mycat.backend.mysql.nio.handler.util.HandlerTool.createFieldItem(HandlerTool.java:248) ~[Action_Mycat-2.17.08.0-dev.jar:?]
	at io.mycat.backend.mysql.nio.handler.util.HandlerTool.createPushDownGroupBy(HandlerTool.java:162) ~[Action_Mycat-2.17.08.0-dev.jar:?]
	at io.mycat.backend.mysql.nio.handler.util.HandlerTool.createItem(HandlerTool.java:98) ~[Action_Mycat-2.17.08.0-dev.jar:?]
	at io.mycat.backend.mysql.nio.handler.query.impl.groupby.OrderedGroupByHandler.fieldEofResponse(OrderedGroupByHandler.java:82) ~[Action_Mycat-2.17.08.0-dev.jar:?]
	at io.mycat.backend.mysql.nio.handler.query.impl.MultiNodeMergeHandler.fieldEofResponse(MultiNodeMergeHandler.java:105) ~[Action_Mycat-2.17.08.0-dev.jar:?]
	at io.mycat.backend.mysql.nio.handler.query.impl.BaseSelectHandler.fieldEofResponse(BaseSelectHandler.java:100) ~[Action_Mycat-2.17.08.0-dev.jar:?]
	at io.mycat.backend.mysql.nio.MySQLConnectionHandler.handleFieldEofPacket(MySQLConnectionHandler.java:192) ~[Action_Mycat-2.17.08.0-dev.jar:?]
	at io.mycat.backend.mysql.nio.MySQLConnectionHandler.handleData(MySQLConnectionHandler.java:118) [Action_Mycat-2.17.08.0-dev.jar:?]
	at io.mycat.net.handler.BackendAsyncHandler$1.run(BackendAsyncHandler.java:55) [Action_Mycat-2.17.08.0-dev.jar:?]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [?:1.8.0_121]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [?:1.8.0_121]
	at java.lang.Thread.run(Thread.java:745) [?:1.8.0_121]
2017-08-31 15:08:35.159  INFO [complexQueryExecutor7] (io.mycat.backend.mysql.nio.handler.query.impl.MultiNodeMergeHandler.fieldEofResponse(MultiNodeMergeHandler.java:94)) - MySQLConnection [id=114, lastTime=1504163315153, user=test, schema=db1, old shema=db1, borrowed=true, fromSlaveDB=false, threadId=2757, charset=utf8, txIsolation=3, autocommit=true, attachment=null, respHandler=io.mycat.backend.mysql.nio.handler.query.impl.BaseSelectHandler@36a1eadb, host=10.186.23.67, port=3306, statusSync=io.mycat.backend.mysql.nio.MySQLConnection$StatusSync@70fff4e4, writeQueue=0, modifiedSQLExecuted=false]'s field is reached.