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  1. Hive
  2. HIVE-72

wrong results if partition pruning not strict and no mep-reduce job needed

    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 0.3.0
    • Component/s: Query Processor
    • Labels:
      None
    • Hadoop Flags:
      Reviewed

      Description

      Suppose T is a partitioned table on ds, where ds is a string column, the following queries:

      SELECT a.* FROM T a WHERE a.ds=2008-09-08 LIMIT 1;
      SELECT a.* FROM T a WHERE a.ds=2008-11-10 LIMIT 1;

      return the first row from the first partition.

      This is because of the typecast to double.

      for a.ds=2008-01-01 or anything (a.ds=1),

      evaluate (Double, Double) is invoked at partition pruning.

      Since '2008-11-01' is not a valid double, it is converted to a null, and therefore the result of pruning returns null (unknown) - not FALSE.
      All unknowns are also accepted, therefore all partitions are accepted which explains this behavior.

      filter is not invoked since it is a select * query, so map-reduce job is started.
      We just turn off this optimization if pruning indicates that there can be unknown partitions.

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            • Assignee:
              namit Namit Jain
              Reporter:
              namit Namit Jain
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              • Created:
                Updated:
                Resolved: