[HIVE-3562] Some limit can be pushed down to map stage

• Type: Bug
• Status: Closed
• Priority: Trivial
• Resolution: Fixed
• Fix Version/s: 0.12.0
• Assignee: Navis Ryu
• Reporter: Navis Ryu
• Created: 10/Oct/12 05:12
• Updated: 14/Sep/21 01:37
• Resolved: 28/Aug/13 15:02

Description

Queries with limit clause (with reasonable number), for example

select * from src order by key limit 10;

makes operator tree,
TS-SEL-RS-EXT-LIMIT-FS

But LIMIT can be partially calculated in RS, reducing size of shuffling.
TS-SEL-RS(TOP-N)-EXT-LIMIT-FS

Issue Links

• is related to: HIVE-12329 Turn on limit pushdown optimization by default
• relates to: HIVE-5093 Use a combiner for LIMIT with GROUP BY and ORDER BY operators
• supercedes: HIVE-5093 Use a combiner for LIMIT with GROUP BY and ORDER BY operators