[DRILL-636] Push Limit operator past project, left outer join, union all operator and down into scan operator

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Fix Version/s: Future
• Component/s: Query Planning & Optimization
• Assignee: Unassigned
• Reporter: Jinfeng Ni
• Created: 05/May/14 18:55
• Updated: 01/Oct/15 16:38

Description

When we have a limit operator on top of project, left outer join, union all operator, we should push the limit operator, until the limit is put into scan operator. Doing so, it will reduce the amount of data scanned by the scan operator.

For instance,

Select COL1, COL2 FROM T1 LIMIT 5;

LIMIT (5)
\
PROJECT (COL1, COL2)
\
SCAN (T1).

We need push limit past project, down into scan.

Similar applies to left outer join, or union all.

Issue Links

• is related to: DRILL-1457 Limit operator optimization : push limit operator past exchange operator