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Posted to dev@parquet.apache.org by "Xinli Shang (Jira)" <ji...@apache.org> on 2020/10/23 16:15:00 UTC
[jira] [Assigned] (PARQUET-1927) ColumnIndex should provide number
of records skipped
[ https://issues.apache.org/jira/browse/PARQUET-1927?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Xinli Shang reassigned PARQUET-1927:
------------------------------------
Assignee: Xinli Shang
> 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
> Assignee: Xinli Shang
> Priority: Major
> 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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