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  1. Spark
  2. SPARK-23852

Parquet MR bug can lead to incorrect SQL results

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    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Blocker
    • Resolution: Fixed
    • Affects Version/s: 2.3.0
    • Fix Version/s: 2.3.1, 2.4.0
    • Component/s: SQL
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      Description

      Parquet MR 1.9.0 and 1.8.2 both have a bug, PARQUET-1217, that means that pushing certain predicates to Parquet scanners can return fewer results than they should.

      The bug triggers in Spark when:

      • The Parquet file being scanner has stats for the null count, but not the max or min on the column with the predicate (Apache Impala writes files like this).
      • The vectorized Parquet reader path is not taken, and the parquet-mr reader is used.
      • A suitable <, <=, > or >= predicate is pushed down to Parquet.

      The bug is that the parquet-mr interprets the max and min of a row-group's column as 0 in the absence of stats. So col > 0 will filter all results, even if some are > 0.

      There is no upstream release of Parquet that contains the fix for PARQUET-1217, although a 1.10 release is planned.

      The least impactful workaround is to set the Parquet configuration parquet.filter.stats.enabled to false.

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              • Assignee:
                rdblue Ryan Blue
                Reporter:
                henryr Henry Robinson
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