Cheng Hao created SPARK-4367:
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Summary: Process the "distinct" value before shuffling for
aggregation
Key: SPARK-4367
URL: https://issues.apache.org/jira/browse/SPARK-4367
Project: Spark
Issue Type: Improvement
Components: SQL
Reporter: Cheng Hao
Most of aggregate function(e.g average) with "distinct" value will requires all
of the records in the same group to be shuffled into a single node, however, as
part of the optimization, those records can be partially aggregated before
shuffling, that probably reduces the overhead of shuffling significantly.
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