[jira] [Created] (SPARK-11580) Just do final aggregation when there is no Exchange

["Yadong Qi (JIRA)" <ji...@apache.org>]

Yadong Qi created SPARK-11580:
---------------------------------

             Summary: Just do final aggregation when there is no Exchange
                 Key: SPARK-11580
                 URL: https://issues.apache.org/jira/browse/SPARK-11580
             Project: Spark
          Issue Type: Improvement
          Components: SQL
    Affects Versions: 1.5.1
            Reporter: Yadong Qi


I do the SQL as below:
{code}
cache table src as select * from src distribute by key;
select key, count(value) from src group by key;
{code}
and the Physical Plan is 
{code}
TungstenAggregate(key=[key#0], functions=[(count(value#1),mode=Final,isDistinct=false)], output=[key#0,_c1#28L])
 TungstenAggregate(key=[key#0], functions=[(count(value#1),mode=Partial,isDistinct=false)], output=[key#0,currentCount#41L])
  InMemoryColumnarTableScan [key#0,value#1], (InMemoryRelation [key#0,value#1], true, 10000, StorageLevel(true, true, false, true, 1), (TungstenExchange hashpartitioning(key#0)), Some(src))
{code}
I think if there is no Exchange, just do final aggregation is better, like:
{code}
TungstenAggregate(key=[key#0], functions=[(count(value#1),mode=Final,isDistinct=false)], output=[key#0,_c1#28L])
  InMemoryColumnarTableScan [key#0,value#1], (InMemoryRelation [key#0,value#1], true, 10000, StorageLevel(true, true, false, true, 1), (TungstenExchange hashpartitioning(key#0)), Some(src))
{code}



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