[C++] Decide if we implement GcsFileSystem::Move

[asfimport]

There is no atomic move in GCS, so maybe we do not need to implement this.

Reporter: Carlos O'Ryan / @coryan
Assignee: Carlos O'Ryan / @coryan

Related issues:

• [C++] Add filesystem / IO implementation for Google Cloud Storage (is a child of)

PRs and other links:

• GitHub Pull Request #11891

_{Note: This issue was originally created as ARROW-14971. Please see the migration documentation for further details.}

[asfimport]

Weston Pace / @westonpace:
As far as I can tell Arrow does not rely on this operation internally. That being said, there is no documented guarantee I can find that the move must be atomic (and the move method in the Windows implementation of local fs is not truly atomic).

[asfimport]

Antoine Pitrou / @pitrou:
Move need not be atomic, but it should probably be "cheap" (i.e. not imply streaming the whole file through the network). If that can't be done, then better to leave it unimplemented, IMHO.

See the S3 implementation:
https://github.com/apache/arrow/blob/master/cpp/src/arrow/filesystem/s3fs.cc#L2377-L2394

[asfimport]

Carlos O'Ryan / @coryan:
For a single object (aka file) it is cheap, it just moves the bytes (and often just the metadata) on the server side.

For buckets is simply cannot be implemented, and for large directories, with many objects, it could be fairly slow (though we could parallelize it).

I have decided to implement the single object case and leave the rest alone.

[asfimport]

Antoine Pitrou / @pitrou:
Issue resolved by pull request 11891
#11891