[HIVE-3773] Share input scan by unions across multiple queries

• Type: Improvement
• Status: In Progress
• Priority: Major
• Resolution: Unresolved
• Component/s: Query Processor
• Assignee: Gang Tim Liu
• Reporter: Namit Jain
• Created: 05/Dec/12 11:08
• Updated: 10/Jan/13 02:54

Description

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.

Issue Links

• is related to: HIVE-2206 add a new optimizer for query correlation discovery and optimization