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From "Jinfeng Ni (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DRILL-636) Push Limit operator past project, left outer join, union all operator and down into scan operator
Date Mon, 05 May 2014 18:57:14 GMT
Jinfeng Ni created DRILL-636:
--------------------------------

             Summary: Push Limit operator past project, left outer join, union all operator
and down into scan operator 
                 Key: DRILL-636
                 URL: https://issues.apache.org/jira/browse/DRILL-636
             Project: Apache Drill
          Issue Type: Improvement
            Reporter: Jinfeng Ni


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.





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