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https://issues.apache.org/jira/browse/HIVE-3638?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13486602#comment-13486602
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Shreepadma Venugopalan commented on HIVE-3638:
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Yes, thats correct. When no splits are generated Hive takes a different code
path and a NULL is emitted from the closeOp() of the groupByOperator. I
originally noticed this problem with hadoop20 after HDFS-3672 was committed. I
believe MAPREDUCE-4470 fixes the behavior on hadoop23 i.e., hadoop23 generates
1 split even when the directory is empty. I checked the behavior on hadoop20
and hadoop23 a month or so back and behavior seemed consistent with the empty
result set. However, NULL is the correct behavior as per the SQL standard. Do
you see this difference in behavior on the latest trunk? Thanks.
> metadataonly1.q test fails with Hadoop23
> ----------------------------------------
>
> Key: HIVE-3638
> URL: https://issues.apache.org/jira/browse/HIVE-3638
> Project: Hive
> Issue Type: Bug
> Components: Tests
> Affects Versions: 0.10.0, 0.9.1
> Reporter: Chris Drome
>
> Hive creates an empty file as a hack to get Hadoop to run a mapper.
> This no longer works with Hadoop23, causing this test to fail. Note that this
> tests empty partitions.
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