Will Jones created ARROW-16761:
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Summary: [C++][Python] Track bytes_written on FileWriter /
WrittenFile
Key: ARROW-16761
URL: https://issues.apache.org/jira/browse/ARROW-16761
Project: Apache Arrow
Issue Type: New Feature
Components: C++, Python
Affects Versions: 8.0.0
Reporter: Will Jones
Fix For: 9.0.0
For Apache Iceberg and Delta Lake tables, we need to be able to get the size of
the files written in bytes. In Iceberg, this is the required field
{{file_size_in_bytes}} ([docs|https://iceberg.apache.org/spec/#manifests]). In
Delta, this is the required field {{size}} as part of the Add action.
I think this could be exposed on
[FileWriter|https://github.com/apache/arrow/blob/8c63788ff7d52812599a546989b7df10887cb01e/cpp/src/arrow/dataset/file_base.h#L305]
and then through that
[WrittenFile|https://github.com/apache/arrow/blob/8c63788ff7d52812599a546989b7df10887cb01e/python/pyarrow/_dataset.pyx#L766-L769].
But lower-level than that I'm not yet sure. {{FileWriter}} owns its
{{OutputStream}}; would {{OutputStream::Tell()}} give the correct count?
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