Henry Robinson created SPARK-23852:
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Summary: Parquet MR bug can lead to incorrect SQL results
Key: SPARK-23852
URL: https://issues.apache.org/jira/browse/SPARK-23852
Project: Spark
Issue Type: Bug
Components: SQL
Affects Versions: 2.3.0
Reporter: Henry Robinson
Parquet 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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