Review Request 42081: HIVE-12788: Setting hive.optimize.union.remove to TRUE will break UNION ALL with aggregate functions

[Chaoyu Tang]

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https://reviews.apache.org/r/42081/
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Review request for hive, Ashutosh Chauhan and Pengcheng Xu.


Bugs: HIVE-12788
    https://issues.apache.org/jira/browse/HIVE-12788


Repository: hive-git


Description
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adds StatsOptimizator support to union with aggregate function. Otherwise, it 
always returns one row.


Diffs
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  ql/src/java/org/apache/hadoop/hive/ql/optimizer/StatsOptimizer.java 03c1c3f 
  ql/src/test/queries/clientpositive/union_remove_26.q PRE-CREATION 
  ql/src/test/results/clientpositive/union_remove_26.q.out PRE-CREATION 

Diff: https://reviews.apache.org/r/42081/diff/


Testing
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1. Manual tests for some partitcular cases
2. submitted to precommit-tests


Thanks,

Chaoyu Tang