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https://issues.apache.org/jira/browse/HIVE-384?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12696173#action_12696173
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Namit Jain commented on HIVE-384:
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The patch has a few bug fixes:
1. The total number of jobs were counted wrongly, which made it very difficult
to debug (specially big union queries).
2. The job name for a query was incorrect, , which made it very difficult to
debug (specially big union queries).
These two are fixed in Driver.java
3. Union plans were very complex and inefficient - since the unions were not
getting merged - the simple fix to to merge
them in the SemanticAnalyzer - no need to check anything, union schema should
be the same.
4. No special case for ReduceSink followed by Union -- the fix is in
GenMRRedSink3
Added a bunch of new tests
> problem in union if the first subquery is a map-only job
> --------------------------------------------------------
>
> Key: HIVE-384
> URL: https://issues.apache.org/jira/browse/HIVE-384
> Project: Hadoop Hive
> Issue Type: Bug
> Reporter: Namit Jain
> Assignee: Namit Jain
> Attachments: hive.384.1.patch, hive.384.2.patch, hive.384.3.patch,
> hive.384.4.patch
>
>
> Union needs special handling.
> explain
> select unionsrc.key, count(1) FROM (select s2.key as key, s2.value as value
> from src1 s2
> UNION ALL
> select 'tst1' as key, cast(count(1) as
> string) as value from src s1)
> unionsrc group by unionsrc.key;
> results in a null pointer exception
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