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https://issues.apache.org/jira/browse/ARROW-11000?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17252958#comment-17252958
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Joris Van den Bossche commented on ARROW-11000:
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The reason I opened this issue is because I saw large download sizes when using
{{s3fs}} to read a single column of a large parquet file (compared to using our
own S3Filesystem, which downloaded only a little bit of data).
So the example basically is the following. But, with the mentioned print
statements, it seems {{PyReadableFile::ReadAt}} also gets called in this case.
So it might be rather an issue on s3fs side?
{code}
In [7]: import s3fs
In [8]: fs2 = s3fs.S3FileSystem(anon=True)
In [9]: pq.read_table('ursa-labs-taxi-data/2016/01/data.parquet',
filesystem=fs2, columns=["passenger_count"])
Calling PyReadableFile::ReadAt
Called seek successfully
....
{code}
> [Python] Enable random access reading for Python file objects (if supported)
> ----------------------------------------------------------------------------
>
> Key: ARROW-11000
> URL: https://issues.apache.org/jira/browse/ARROW-11000
> Project: Apache Arrow
> Issue Type: Improvement
> Components: Python
> Reporter: Joris Van den Bossche
> Priority: Major
>
> {{arrow::py::PyReadableFile::ReadAt}} is being commented as thread-safe (it
> puts a lock on the underlying python file) and should thus allow random
> access in parallel code (for example, reading a subset (eg column) of a
> parquet file).
> However, based on experimentation, it seems this doesn't work (eg with s3fs
> filesystem to read a specific parquet column
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