Phoenix500526 opened a new pull request, #24923:
URL: https://github.com/apache/datafusion/pull/24923
## Which issue does this PR close?
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- Closes #23247.
## Rationale for this change
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`SpillFile` supports asynchronous reads, but spill writes currently use
`std::io::Write`. Backends built on asynchronous storage APIs must either block
while uploading data or buffer an entire spill file in memory before uploading
it.
This PR adds an asynchronous spill writing path so remote backends can
upload spill data as Arrow IPC buffers are produced.
## What changes are included in this PR?
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sometimes worth providing a summary of the individual changes in this PR.
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- Add the public `AsyncSpillWriter` trait and `SpillFile::open_async_writer`.
- Preserve compatibility with existing `SpillFile` implementations through a
default adapter backed by `open_writer`.
- Separate Arrow IPC stream encoding from I/O so encoded buffers can be sent
to synchronous or asynchronous writers.
- Migrate external sort and stream-based spill herlpers to the asychronous
writing path.
- Keep memory reservations active while batches are waiting for asynchronous
writes to complete.
- And best-effort cleanup for incomplete uploads after errors or query
cancellation.
- Update the object store spill example to stream data through multipart
uploads instread of buffering the complete spill file in memory.
Spill paths that require a partially written local file to remain readable
continue to use the synchronous API.
## What is the testing strategy for this PR?
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The added tests cover:
- Arrow IPC round trips through an asynchronous spill writer.
- Cleanup after write errors, failed aborts, and task cancellation.
- Memory accounting while an asynchronous spill write is pending.
- Multipart part uploads before `finish` is called.
- Releasing the source Arrow allocation when a small multipart tail is
buffered.
The object store spill example was also run end to end. The full workspace
test suite, extended tests, Clippy, Rustdoc, and repository lint checks pass.
## Are there any user-facing changes?
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Yes. Custom spill backends can implement `AsyncSpillWriter` and override
`SpillFile::open_async_writer` to use asynchronous storage APIs directly.
This is an additive API change. Existing synchronous `SpillFile`
implementations continue to work through the default adapter and do not need to
be updated.
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