GH-26818: [C++][Python] Preserve order when writing dataset multi-threaded (#44470)#5
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EnricoMi merged 2 commits intoG-Research:20.0.0-grfrom May 23, 2025
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…ti-threaded (apache#44470) ### Rationale for this change The order of rows in a dataset might be important for users and should be preserved when writing to a filesystem. With multi-threaded write, the order is currently not guaranteed, ### What changes are included in this PR? Preserving the dataset order of rows requires the `SourceNode` to sequence the fragments output (this keeps exec batches in the order of fragments), to provide an `ImplicitOrdering` (this gives exec batches an index), and the `ConsumingSinkNode` to sequence exec batches (finally preserve order of batches according to their index). User-facing changes: - Add option `preserve_order` to `FileSystemDatasetWriteOptions` (C++) and `arrow.dataset.write_dataset` (Python). Default behaviour is current behaviour. ### Are these changes tested? Unit tests have been added, ### Are there any user-facing changes? Users can set `FileSystemDatasetWriteOptions.preserve_order = true` (C++) / `arrow.dataset.write_dataset(..., preserve_order=True)` (Python). * GitHub Issue: apache#26818 Lead-authored-by: Enrico Minack <github@enrico.minack.dev> Co-authored-by: Rok Mihevc <rok@mihevc.org> Signed-off-by: Rok Mihevc <rok@mihevc.org>
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❌ GitHub issue apache#26818 could not be retrieved. |
adamreeve
approved these changes
May 23, 2025
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Backports apache#44470 to 20.0.0-gr.
Rationale for this change
The order of rows in a dataset might be important for users and should be preserved when writing to a filesystem. With multi-threaded write, the order is currently not guaranteed,
What changes are included in this PR?
Preserving the dataset order of rows requires the
SourceNodeto sequence the fragments output (this keeps exec batches in the order of fragments), to provide anImplicitOrdering(this gives exec batches an index), and theConsumingSinkNodeto sequence exec batches (finally preserve order of batches according to their index).User-facing changes:
preserve_ordertoFileSystemDatasetWriteOptions(C++) andarrow.dataset.write_dataset(Python).Default behaviour is current behaviour.
Are these changes tested?
Unit tests have been added,
Are there any user-facing changes?
Users can set
FileSystemDatasetWriteOptions.preserve_order = true(C++) /arrow.dataset.write_dataset(..., preserve_order=True)(Python).Lead-authored-by: Enrico Minack github@enrico.minack.dev
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Rationale for this change
What changes are included in this PR?
Are these changes tested?
Are there any user-facing changes?
This PR includes breaking changes to public APIs. (If there are any breaking changes to public APIs, please explain which changes are breaking. If not, you can remove this.)
This PR contains a "Critical Fix". (If the changes fix either (a) a security vulnerability, (b) a bug that caused incorrect or invalid data to be produced, or (c) a bug that causes a crash (even when the API contract is upheld), please provide explanation. If not, you can remove this.)