Apache Drill
  1. Apache Drill
  2. DRILL-636

Push Limit operator past project, left outer join, union all operator and down into scan operator

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      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.

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            • Assignee:
              Unassigned
              Reporter:
              Jinfeng Ni
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              • Created:
                Updated:

                Development