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  1. Hive
  2. HIVE-960

Lateral View optimizations

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    Details

    • Type: New Feature
    • Status: Open
    • Priority: Major
    • Resolution: Unresolved
    • Affects Version/s: None
    • Fix Version/s: None
    • Component/s: Query Processor
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      Description

      Had a offline discussion with Paul yesterday.

      This is a followup on https://issues.apache.org/jira/browse/HIVE-935
      Say, the query is

      select .. from T LATERAL VIEW explode(c2_list) as c2 LATERAL VIEW explode(c3_list) as c3

      If we follow the suggestion from https://issues.apache.org/jira/browse/HIVE-935,
      (Lateral View Join operator will always have 2 inputs - the inputs will not be merged like join),
      the explode operator for c3_list will be called once for each input on c2, which can be expensive.

      Instead, if we merge the inputs and let LATERAL VIEW have 3 inputs, we will be invoking explode
      operator for c3_list once for each row.

      So, merging should be performed when the right side lateral views are not referencing anything from the
      left side lateral views.

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              • Assignee:
                pauly Paul Yang
                Reporter:
                namit Namit Jain
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                • Created:
                  Updated: