Correlation Optimizer lead to NPE when there's multi subquery(select distinct) union all operation after join

SELECT DISTINCT a.logday AS push_day, a.mtype, a.t, If(b.msgid IS NULL, 'no', 'yes') AS isnotdaoda, a.platform
    , a.uid, a.dt
FROM (SELECT DISTINCT If(tokentype = '7', msgid, If(tokentype = '6', regexp_extract(sendpushresult, 'msgId":"([^"]+)', 1), regexp_extract(sendpushresult, 'msgId=(.+?),', 1))) AS msgid, logday, If(vid LIKE '60%', 'adr', If(vid LIKE '8%', 'ios', 'other')) AS platform, mtype, t
        , If(vid LIKE '8%', uid, gid) AS uid, concat(substr(logday, 1, 4), '-', substr(logday, 5, 2), '-', substr(logday, 7, 2)) AS dt
    FROM wirelessdata.orig_push_client
    ) a
    LEFT JOIN (SELECT DISTINCT msgid
        FROM (
            SELECT DISTINCT msgid
            FROM wirelessdata.orig_push_return
            UNION ALL
            SELECT DISTINCT msgid
            FROM wirelessdata.orig_push_return_xiaomi
            UNION ALL
            SELECT DISTINCT regexp_extract(action, '"id"："([^"]+)', 1) AS msgid
            FROM wirelessdata.ods_client_behavior_hour4spark
        ) bb
        ) b ON lower(a.msgid) = lower(b.msgid)

2017-11-10T16:01:21,123 ERROR [9b7d82f5-dfc8-43ac-8d6f-a019d8677392 main] ql.Driver: FAILED: NullPointerException null
java.lang.NullPointerException
	at org.apache.hadoop.hive.ql.optimizer.GenMapRedUtils.setUnionPlan(GenMapRedUtils.java:230)
	at org.apache.hadoop.hive.ql.optimizer.GenMapRedUtils.joinUnionPlan(GenMapRedUtils.java:287)
	at org.apache.hadoop.hive.ql.optimizer.GenMRRedSink3.process(GenMRRedSink3.java:100)
	at org.apache.hadoop.hive.ql.lib.DefaultRuleDispatcher.dispatch(DefaultRuleDispatcher.java:90)
	at org.apache.hadoop.hive.ql.lib.DefaultGraphWalker.dispatchAndReturn(DefaultGraphWalker.java:105)
	at org.apache.hadoop.hive.ql.parse.GenMapRedWalker.walk(GenMapRedWalker.java:54)
	at org.apache.hadoop.hive.ql.parse.GenMapRedWalker.walk(GenMapRedWalker.java:65)
	at org.apache.hadoop.hive.ql.parse.GenMapRedWalker.walk(GenMapRedWalker.java:65)
	at org.apache.hadoop.hive.ql.parse.GenMapRedWalker.walk(GenMapRedWalker.java:65)
	at org.apache.hadoop.hive.ql.parse.GenMapRedWalker.walk(GenMapRedWalker.java:65)
	at org.apache.hadoop.hive.ql.parse.GenMapRedWalker.walk(GenMapRedWalker.java:65)
	at org.apache.hadoop.hive.ql.parse.GenMapRedWalker.walk(GenMapRedWalker.java:65)
	at org.apache.hadoop.hive.ql.parse.GenMapRedWalker.walk(GenMapRedWalker.java:65)
	at org.apache.hadoop.hive.ql.parse.GenMapRedWalker.walk(GenMapRedWalker.java:65)
	at org.apache.hadoop.hive.ql.parse.GenMapRedWalker.walk(GenMapRedWalker.java:65)
	at org.apache.hadoop.hive.ql.lib.DefaultGraphWalker.startWalking(DefaultGraphWalker.java:120)
	at org.apache.hadoop.hive.ql.parse.MapReduceCompiler.generateTaskTree(MapReduceCompiler.java:323)
	at org.apache.hadoop.hive.ql.parse.TaskCompiler.compile(TaskCompiler.java:267)
	at org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.analyzeInternal(SemanticAnalyzer.java:11008)
	at org.apache.hadoop.hive.ql.parse.SemanticAnalyzer.analyzeInternal(SemanticAnalyzer.java:10547)
	at org.apache.hadoop.hive.ql.parse.BaseSemanticAnalyzer.analyze(BaseSemanticAnalyzer.java:250)
	at org.apache.hadoop.hive.ql.Driver.compile(Driver.java:483)
	at org.apache.hadoop.hive.ql.Driver.compileInternal(Driver.java:1254)
	at org.apache.hadoop.hive.ql.Driver.runInternal(Driver.java:1396)
	at org.apache.hadoop.hive.ql.Driver.run(Driver.java:1181)
	at org.apache.hadoop.hive.ql.Driver.run(Driver.java:1170)
	at org.apache.hadoop.hive.cli.CliDriver.processLocalCmd(CliDriver.java:229)
	at org.apache.hadoop.hive.cli.CliDriver.processCmd(CliDriver.java:180)
	at org.apache.hadoop.hive.cli.CliDriver.processLine(CliDriver.java:396)
	at org.apache.hadoop.hive.cli.CliDriver.executeDriver(CliDriver.java:770)
	at org.apache.hadoop.hive.cli.CliDriver.run(CliDriver.java:711)
	at org.apache.hadoop.hive.cli.CliDriver.main(CliDriver.java:638)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:497)
	at org.apache.hadoop.util.RunJar.main(RunJar.java:212)