Namit Jain created HIVE-3773:
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Summary: Share input scan by unions across multiple queries
Key: HIVE-3773
URL: https://issues.apache.org/jira/browse/HIVE-3773
Project: Hive
Issue Type: Improvement
Components: Query Processor
Reporter: Namit Jain
Assignee: Namit Jain
Consider a query like:
select * from
(
select key, 1 as value, count(1) from src group by key
union all
select 1 as key, value, count(1) from src group by value
union all
select key, value, count(1) from src group by key, value
) s;
src is scanned multiple times currently (one per sub-query).
This should be treated like a multi-table insert by the optimizer.
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