Jan-Erik Hedbom created HIVE-6057:
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Summary: Enable bucketed sorted merge joins of arbitrary subqueries
Key: HIVE-6057
URL: https://issues.apache.org/jira/browse/HIVE-6057
Project: Hive
Issue Type: Improvement
Components: Query Processor
Affects Versions: 0.12.0
Reporter: Jan-Erik Hedbom
Priority: Minor
Currently, you cannot use bucketed SMJ when joining subquery results. It would
make sense to be able to explicitly specify bucketing of the intermediate
output from a subquery to enable bucketed SMJ.
For example, the following query will NOT use bucketed SMJ:
(gameends and dummymapping are clustered and sorted by hashid into 128 buckets)
select * from (select hashid,count(*) as c from gameends group by hashid
distribute by hashid sort by hashid) e join dummymapping m on e.hashid=m.hashid
Suggestion: Implement an INTO n BUCKETS syntax for subqueries to enable
bucketed SMJ:
select * from (select hashid,count(*) as c from gameends group by hashid
distribute by hashid sort by hashid INTO 128 BUCKETS) e join dummymapping m on
e.hashid=m.hashid
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