[jira] [Created] (HIVE-3773) Share input scan by unions across multiple queries

["Namit Jain (JIRA)" <ji...@apache.org>]

Namit Jain created HIVE-3773:
--------------------------------

             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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