[jira] [Created] (SPARK-22536) VectorizedParquetRecordReader doesn't use Parquet's dictionary filtering feature

["Ivan Gozali (JIRA)" <ji...@apache.org>]

Ivan Gozali created SPARK-22536:
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             Summary: VectorizedParquetRecordReader doesn't use Parquet's dictionary filtering feature
                 Key: SPARK-22536
                 URL: https://issues.apache.org/jira/browse/SPARK-22536
             Project: Spark
          Issue Type: Improvement
          Components: SQL
    Affects Versions: 2.2.0
         Environment: Spark 2.2.0
            Reporter: Ivan Gozali


The VectorizedParquetRecordReader currently only uses statistics filtering, and does not make use of dictionary filtering in Parquet. Having dictionary filtering would be very useful for string/binary columns that have low cardinality

Some relevant code paths:
* https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetFileFormat.scala#L367-L387 When vectorizedReader is enabled, the code will use VectorizedParquetRecordReader, which uses SpecificParquetRecordReaderBase below
* https://github.com/apache/spark/blob/master/sql/core/src/main/java/org/apache/spark/sql/execution/datasources/parquet/SpecificParquetRecordReaderBase.java#L109 This is where the row group filtering is being performed. It calls the method below
* https://github.com/apache/parquet-mr/blob/apache-parquet-1.8.2/parquet-hadoop/src/main/java/org/apache/parquet/filter2/compat/RowGroupFilter.java#L64-L70

The RowGroupFilter constructor used in Spark's {{VectorizedParquetRecordReader}} hard-codes the {{FilterLevel}} used to only {{FilterLevel.STATISTICS}}, and is deprecated.
{code}
  @Deprecated
  private RowGroupFilter(List<BlockMetaData> blocks, MessageType schema) {
    this.blocks = checkNotNull(blocks, "blocks");
    this.schema = checkNotNull(schema, "schema");
    this.levels = Collections.singletonList(FilterLevel.STATISTICS);
    this.reader = null;
{code}

Compare this to {{org.apache.parquet.hadoop.ParquetRecordReader.initialize()}}, which uses the second RowGroupFilter constructor that allows it to set the {{FilterLevel}}. Relevant code here:
https://github.com/apache/parquet-mr/blob/master/parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetRecordReader.java#L166-L182






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