Jesus Camacho Rodriguez created HIVE-17037:
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Summary: Extend join algorithm selection to avoid unnecessary
input data shuffle
Key: HIVE-17037
URL: https://issues.apache.org/jira/browse/HIVE-17037
Project: Hive
Issue Type: Improvement
Components: Physical Optimizer
Affects Versions: 3.0.0
Reporter: Jesus Camacho Rodriguez
Assignee: Jesus Camacho Rodriguez
As an example, consider the following query:
{code:sql}
SELECT *
FROM (
SELECT a.value
FROM src1 a
JOIN src1 b
ON (a.value = b.value)
GROUP BY a.value
) a
JOIN src
ON (a.value = src.value);
{code}
Currently, the plan generated for Tez will contain an unnecessary shuffle
operation between the subquery and the join, since the records produced by the
subquery are already sorted by the value.
This issue is to extend join algorithm selection to be able to shuffle only
some of the inputs for a given join and avoid unnecessary shuffle operations.
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