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Posted to dev@parquet.apache.org by "Xinli Shang (Jira)" <ji...@apache.org> on 2020/10/17 14:43:00 UTC

[jira] [Created] (PARQUET-1927) ColumnIndex should provide number of records skipped

Xinli Shang created PARQUET-1927:
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             Summary: ColumnIndex should provide number of records skipped 
                 Key: PARQUET-1927
                 URL: https://issues.apache.org/jira/browse/PARQUET-1927
             Project: Parquet
          Issue Type: Improvement
          Components: parquet-mr
    Affects Versions: 1.11.0
            Reporter: Xinli Shang
             Fix For: 1.12.0


When integrating Parquet ColumnIndex, I found we need to know from Parquet that how many records that we skipped due to ColumnIndex filtering. When rowCount is 0, readNextFilteredRowGroup() just advance to next without telling the caller. See code here [https://github.com/apache/parquet-mr/blob/master/parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileReader.java#L969]

 

In Iceberg, it reads Parquet record with an iterator. The hasNext() has the following code():

valuesRead + skippedValues < totalValues

See ([https://github.com/apache/iceberg/pull/1566/commits/cd70cac279d3f14ba61f0143f9988d4cc9413651#diff-d80c15b3e5376265436aeab8b79d5a92fb629c6b81f58ad10a11b9b9d3bfcffcR115).] 

So without knowing the skipped values, it is hard to determine hasNext() or not. 

 

Currently, we can workaround by using a flag. When readNextFilteredRowGroup() returns null, we consider it is done for the whole file. Then hasNext() just retrun false. 

 

 

 



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