apache / apache/parquet-java

ColumnIndex should provide number of records skipped

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#2,536 17 comments 0 reactions 0 assignees View on GitHub
Component: Java Component: Parquet Priority: Major Type: enhancement
Dominant language
Java
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Description

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

 

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

valuesRead + skippedValues < totalValues

See ( 

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. 

 

 

 

**Reporter**: [Xinli Shang](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=shangxinli) / @shangxinli
**Assignee**: [Xinli Shang](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=shangx@uber.com) / @shangxinli

**Note**: *This issue was originally created as [PARQUET-1927](https://issues.apache.org/jira/browse/PARQUET-1927). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*

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Research direction

Start in parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileReader.java at readNextFilteredRowGroup(), then compare the iterator hasNext() logic in the linked Iceberg change. Trace how a row group with rowCount 0 advances and determine how the skipped record count should reach the caller; done means callers can reliably determine whether records remain after ColumnIndex filtering.

Written by the indexing model from the issue text.

Assessment

Tech stack
java
Domain
data-engineering
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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