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

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

Joris Van den Bossche created ARROW-8733:
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             Summary: [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
             Fix For: 1.0.0


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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