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https://issues.apache.org/jira/browse/PARQUET-1537?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Valery Meleshkin updated PARQUET-1537:
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    Attachment: example.parquet

> [C++] The patch for PARQUET-1508 leads to infinite loop and infinite memory 
> allocation when reading very sparse ByteArray columns
> ---------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: PARQUET-1537
>                 URL: https://issues.apache.org/jira/browse/PARQUET-1537
>             Project: Parquet
>          Issue Type: Bug
>          Components: parquet-cpp
>            Reporter: Valery Meleshkin
>            Assignee: Hatem Helal
>            Priority: Major
>             Fix For: cpp-1.6.0
>
>         Attachments: example.parquet
>
>
> In this loop
> [https://github.com/apache/arrow/commit/3d435e4f8d5fb7a54a4a9d285e1a42d60186d8dc#diff-47fe879cb9baad6c633c55f0a34a09c3R739]
> The branch of if dealing with null values does not increment variable 'i'. 
> Therefore on chunks containing only NULLs once a thread enters the loop, it 
> stays in that loop forever. I'm not entirely sure whether 'num_values' 
> variable was meant to be the number of non-NULL values, yet the total number 
> of values is passed here 
> [https://github.com/apache/arrow/blob/3d435e4f8d5fb7a54a4a9d285e1a42d60186d8dc/cpp/src/parquet/arrow/record_reader.cc#L528]
>  
> On my local machine adding `++i` to the NULL-handling branch seems to fix the 
> problem. Unfortunately, I'm not familiar with the codebase enough to be 
> certain it's a proper fix.



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