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https://issues.apache.org/jira/browse/HIVE-3915?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13557311#comment-13557311
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Hudson commented on HIVE-3915:
------------------------------
Integrated in Hive-trunk-h0.21 #1921 (See
[https://builds.apache.org/job/Hive-trunk-h0.21/1921/])
HIVE-3915 Union with map-only query on one side and two MR job query on the
other
produces wrong results (Kevin Wilfong via namit) (Revision 1435203)
Result = FAILURE
namit : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1435203
Files :
* /hive/trunk/ql/src/java/org/apache/hadoop/hive/ql/Driver.java
* /hive/trunk/ql/src/java/org/apache/hadoop/hive/ql/optimizer/GenMRUnion1.java
* /hive/trunk/ql/src/test/queries/clientpositive/union33.q
* /hive/trunk/ql/src/test/results/clientpositive/union33.q.out
> Union with map-only query on one side and two MR job query on the other
> produces wrong results
> ----------------------------------------------------------------------------------------------
>
> Key: HIVE-3915
> URL: https://issues.apache.org/jira/browse/HIVE-3915
> Project: Hive
> Issue Type: Bug
> Components: Query Processor
> Affects Versions: 0.11.0
> Reporter: Kevin Wilfong
> Assignee: Kevin Wilfong
> Fix For: 0.11.0
>
> Attachments: HIVE-3915.1.patch.txt
>
>
> When a query contains a union with a map only subquery on one side and a
> subquery involving two sequential map reduce jobs on the other, it can
> produce wrong results. It appears that if the map only queries table scan
> operator is processed first the task involving a union is made a root task.
> Then when the other subquery is processed, the second map reduce job gains
> the task involving the union as a child and it is made a root task. This
> means that both the first and second map reduce jobs are root tasks, so the
> dependency between the two is ignored. If they are run in parallel (i.e. the
> cluster has more than one node) no results will be produced for the side of
> the union with the two map reduce jobs and only the results of the other side
> of the union will be returned.
> The order TableScan operators are processed is crucial to reproducing this
> bug, and it is determined by the order values are retrieved from a map, and
> hence hard to predict, so it doesn't always reproduce.
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