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https://issues.apache.org/jira/browse/PARQUET-2443?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17823825#comment-17823825
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Gang Wu commented on PARQUET-2443:
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I need take some time to read related code to get familiar with the context.
In the meanwhile, Apache Iceberg uses an iterator pattern to read from values,
pages and even files. It may be helpful to check this out if you haven't:
https://github.com/apache/iceberg/blob/2519ab43d654927802cc02e19c917ce90e8e0265/parquet/src/main/java/org/apache/iceberg/parquet/BasePageIterator.java#L40
> Support lazy materialization of row groups in ParquetFileReader
> ---------------------------------------------------------------
>
> Key: PARQUET-2443
> URL: https://issues.apache.org/jira/browse/PARQUET-2443
> Project: Parquet
> Issue Type: Improvement
> Reporter: Claire McGinty
> Priority: Major
>
> Motivation: The current behavior of ParquetFilterReader#readNextRowGroup is
> to eagerly enumerate all chunks in the row group, then read all pages in the
> chunk. For distributed data workloads, this can cause significant memory
> pressure, particularly for use cases that require the colocation of multiple
> Parquet files on a single worker.
>
> Proposal: A Parquet Configuration option that enables lazy row group reading,
> i.e., only a page at a time (plus whatever header is necessary to read that
> header). The Configuration option could be either a flag, or an int value for
> how many pages/page bytes to buffer at a time.
>
> I think this could be accomplished by modifying
> [ParquetFileReader#readAllPages|https://github.com/apache/parquet-mr/blob/cf294a35ca4b635f44357fe4c170f3b66870dc6e/parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileReader.java#L1727]
> to re-implement pagesInChunk as an Iterator<DataPage>, rather than a
> List<DataPage>. Then, ColumnChunkPageReader could parse the Configuration
> option above and decide whether to fully materialize the iterator or not.
>
> I'm happy to try to create a draft/branch for this to get some early feedback
> on the idea!
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