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Posted to dev@hive.apache.org by "Harish Butani (JIRA)" <ji...@apache.org> on 2013/10/31 18:27:22 UTC
[jira] [Created] (HIVE-5709) Extend Join merging logic to merge 2
Joins when one Join expression list is a subset of the other.
Harish Butani created HIVE-5709:
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Summary: Extend Join merging logic to merge 2 Joins when one Join expression list is a subset of the other.
Key: HIVE-5709
URL: https://issues.apache.org/jira/browse/HIVE-5709
Project: Hive
Issue Type: Improvement
Components: Query Processor
Reporter: Harish Butani
As pointed out by [~ashutoshc] here: https://reviews.apache.org/r/14953/
For the following query
{noformat}
select p1.name, p2.name, p3.name
from part p1 join p2 on p1.name = p2.name and p1.key = p2.key join
part p3 on p1.name = p3.name
{noformat}
2 jobs are generated:
- p1 join p2 on name, key
- join p3 on name
This can be done as:
- 1 3-way join of p1,p2,p3 on name
- followed by a Filter on p1.key = p2.key
This is valid only for inner joins.
This can be done by extending the Merge Join logic to check for a subset relation between 2 QBJoinTree expression lists.
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