[jira] [Assigned] (ARROW-3020) [Python] Addition of option to allow empty Parquet row groups

["Wes McKinney (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-3020?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Wes McKinney reassigned ARROW-3020:
-----------------------------------

    Assignee: Wes McKinney

> [Python] Addition of option to allow empty Parquet row groups
> -------------------------------------------------------------
>
>                 Key: ARROW-3020
>                 URL: https://issues.apache.org/jira/browse/ARROW-3020
>             Project: Apache Arrow
>          Issue Type: New Feature
>          Components: C++, Python
>            Reporter: Alex Mendelson
>            Assignee: Wes McKinney
>            Priority: Major
>              Labels: parquet, pull-request-available
>             Fix For: 0.12.0
>
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> While our use case is not common, I was able to find one related request from roughly a year ago. Could this be added as a feature?
> https://issues.apache.org/jira/browse/PARQUET-1047
> *Motivation*
> We have an application where each row is associated with one of N contexts, though a minority of contexts may have no associated rows. When encountering the Nth context, we will wish to retrieve all the associated rows. Row groups would provide a natural way to index the data, as the nth context could naturally relate to the nth row group.
> Unfortunately, this is not possible at the present time, as pyarrow does not support writing empty row groups. If one writes a pyarrow.Table containing zero rows using pyarrow.parquet.ParquetWriter, it is omitted from the final file, and this distorts the indexing.



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