[jira] [Updated] (ARROW-8733) [C++][Dataset][Python] ParquetFileFragment should provide access to parquet FileMetadata

["Joris Van den Bossche (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ARROW-8733?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Joris Van den Bossche updated ARROW-8733:
-----------------------------------------
    Fix Version/s:     (was: 1.0.0)

> [C++][Dataset][Python] ParquetFileFragment should provide access to parquet FileMetadata
> ----------------------------------------------------------------------------------------
>
>                 Key: ARROW-8733
>                 URL: https://issues.apache.org/jira/browse/ARROW-8733
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: C++, Python
>            Reporter: Joris Van den Bossche
>            Priority: Major
>              Labels: dataset
>
> Related to ARROW-8062 (as there we will also need a way to expose the global FileMetadata). But independently, it would be useful to get access to the FileMetadata on each {{ParquetFileFragment}} (eg to get access to the statistics).
> This would be relatively simple to code on the Python/R side, since we have access to the file path, and could read the metadata from the file backing the fragment, and return this as a FileMetadata object. 
> I am wondering if we want to integrate this with ARROW-8062, since when the fragments were created from a {{_metadata}} file, a {{ParquetFileFragment.metadata}} attribute would not need to read it from the parquet file in this case, but from the global metadata (at least for eg the row group data).
> Another question: what for a ParquetFileFragment that maps to a single row group?



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