Namit Jain created HIVE-4137:
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Summary: optimize group by followed by joins for bucketed/sorted
tables
Key: HIVE-4137
URL: https://issues.apache.org/jira/browse/HIVE-4137
Project: Hive
Issue Type: Improvement
Components: Query Processor
Reporter: Namit Jain
Consider the following scenario:
create table T1 (...) clustered by (key) sorted by (key) into 2 buckets;
create table T2 (...) clustered by (key) sorted by (key) into 2 buckets;
create table T3 (...) clustered by (key) sorted by (key) into 2 buckets;
SET hive.enforce.sorting=true;
SET hive.enforce.bucketing=true;
insert overwrite table T3
select ..
from
(select key, aggr() from T1 group by key) s1
full outer join
(select key, aggr() from T2 group by key) s2
on s1.key=s2.ley;
Ideally, this query can be performed in a single map-only job.
Group By -> SortMerge Join.
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