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https://issues.apache.org/jira/browse/ARROW-1983?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16818319#comment-16818319
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Matthew Rocklin commented on ARROW-1983:
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My understanding is that there is already a standard around using a "_metadata" 
file that presumably is expected to have certain data laid out in a certain 
way.  It may be that [~mdurant] can provide a nice reference to the 
expectations.

It also looks like PyArrow has a nice reader for this information.  If I open 
up a Parquet Dataset that has a `_metadata` file I find that my object has all 
of the right information, so that might also be a good place to look.

> [Python] Add ability to write parquet `_metadata` file
> ------------------------------------------------------
>
>                 Key: ARROW-1983
>                 URL: https://issues.apache.org/jira/browse/ARROW-1983
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: C++, Python
>            Reporter: Jim Crist
>            Priority: Major
>              Labels: beginner, parquet
>             Fix For: 0.14.0
>
>
> Currently {{pyarrow.parquet}} can only write the {{_common_metadata}} file 
> (mostly just schema information). It would be useful to add the ability to 
> write a {{_metadata}} file as well. This should include information about 
> each row group in the dataset, including summary statistics. Having this 
> summary file would allow filtering of row groups without needing to access 
> each file beforehand.
> This would require that the user is able to get the written RowGroups out of 
> a {{pyarrow.parquet.write_table}} call and then give these objects as a list 
> to new function that then passes them on as C++ objects to {{parquet-cpp}} 
> that generates the respective {{_metadata}} file.



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