Davies Liu created SPARK-12213:
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             Summary: Query with only one distinct should not having on expand
                 Key: SPARK-12213
                 URL: https://issues.apache.org/jira/browse/SPARK-12213
             Project: Spark
          Issue Type: Improvement
            Reporter: Davies Liu


Expand will double the number of records, slow down projection and aggregation, 
it's better to generate a plan without Expand for a query with only one 
distinct (for example, ss_max in TPCDS)



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