[HIVE-1392] minimize execution for (sub)queries which are guaranteed to return no results

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 0.5.0
• Component/s: Query Processor
• Labels: optimization
• Assignee: Unassigned
• Reporter: John Sichi
• Created: 04/Jun/10 18:50
• Updated: 05/Apr/11 22:07

Description

Examples would be a predicate like

WHERE 1=0

or

WHERE ds='2010-01-01'

if the table is partitioned on ds and no partition exists for that date.

Per HIVE-838, we have to be careful with the relational algebra analysis; operators like union, outer join, and full-table aggregation can cause rows to be produced even when one of the inputs is guaranteed to be completely filtered out.