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https://issues.apache.org/jira/browse/HIVE-22198?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16934016#comment-16934016
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LuGuangMing commented on HIVE-22198:
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【analyze】
explain SELECT sum(1) as a
FROM tab1 t1
INNER JOIN tab2 t2
ON t1.com = t2.com
UNION ALL
SELECT sum(1) as a
FROM tab3 t3
INNER JOIN tab4 t4
ON t3.com = t4.com;
!image-2019-09-20-11-38-37-433.png|width=456,height=176!!image-2019-09-20-11-39-30-347.png|width=378,height=303!
Analysis explian plan and resouce code, shows that stage-3 is added to the
runnable queue when one of stage-2 or stage-6 runs is finished, due to
ConditionalTask stage-9 and ConditionalTask stage-11 was invoked by parallel,
remove the parent dependency of stage-3 on stage-2 and stage-6, The Driver
scheduler finds that one of the stage-2 or stage-6 runtimes is finished, The
children stage-3 will be found for scheduling add to runnable queue to run, At
this time, there is still one node in stage-2 or stage-6 that has not run
finished, and the result of the stage that has not finished will not be read by
stage-3, so part of the result data is missing
> Execute unoin-all with childs Join in parallel
> ----------------------------------------------
>
> Key: HIVE-22198
> URL: https://issues.apache.org/jira/browse/HIVE-22198
> Project: Hive
> Issue Type: Bug
> Affects Versions: 1.2.0, 3.0.0, 3.1.0
> Reporter: LuGuangMing
> Assignee: LuGuangMing
> Priority: Major
> Attachments: image-2019-09-20-11-38-37-433.png,
> image-2019-09-20-11-39-30-347.png, test-parallel.sql
>
>
> set parallel is true, set skewjoin is false, set auto convert join is false.
> run a unoin all, There is nothing error message, but some result data is
> missing, details check attatchment sql file
> create table tab1(tid int, com string) row format delimited fields terminated
> by '\t' stored as textfile;
> create table tab2(tid int, com string) row format delimited fields
> terminated by '\t' stored as textfile;
> create table tab3(tid int, com string) row format delimited fields
> terminated by '\t' stored as textfile;
> create table tab4(tid int, com string) row format delimited fields
> terminated by '\t' stored as textfile;
> insert into tab1 values(1,'abc'),(2,'bcd'),(3,'cde');
> insert into tab2 values(1,'abc'),(2,'bcd'),(3,'cde');
> insert into tab3 values(1,'abc'),(2,'bcd'),(3,'cde');
> insert into tab4 values(1,'abc'),(2,'bcd'),(3,'cde');
> set hive.auto.convert.join=false;
> set hive.optimize.skewjoin=true;
> set hive.exec.parallel=true;
> SELECT sum(1) as a
> FROM tab1 t1
> INNER JOIN tab2 t2
> ON t1.com = t2.com
> UNION ALL
> SELECT sum(1) as a
> FROM tab3 t3
> INNER JOIN tab4 t4
> ON t3.com = t4.com;
> create table test_parallel stored as orcfile as
> SELECT sum(1) as a
> FROM tab1 t1
> INNER JOIN tab2 t2
> ON t1.com = t2.com
> UNION ALL
> SELECT sum(1) as a
> FROM tab3 t3
> INNER JOIN tab4 t4
> ON t3.com = t4.com;
> select * from test_parallel;
> The result data should be two, but only one.
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