fix: try again to fix Miri in ParquetOpener#21680
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mbutrovich merged 2 commits intoapache:mainfrom Apr 16, 2026
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Testing the fix in Comet CI: apache/datafusion-comet#3960 |
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Miri is green in Comet CI with the latest commit: https://github.com/apache/datafusion-comet/actions/runs/24522903075/job/71685242268?pr=3960 |
comphead
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| let result = self.project_batch(&batch); | ||
| timer.stop(); | ||
| return Some(result); | ||
| // Release the borrow on baseline_metrics before moving self |
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Thanks @mbutrovich IMO it is good to go.
alamb
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| /// - [`Finished`](DecodeResult::Finished) – signals end-of-stream (`None`). | ||
| async fn transition(&mut self) -> Option<Result<RecordBatch>> { | ||
| /// | ||
| /// Takes `self` by value (rather than `&mut self`) so the generated future |
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Which issue does this PR close?
PushDecoderStreamState::transition#21662.Rationale for this change
#21663 removed the nested async block in
PushDecoderStreamState::transitionto fix a Stacked Borrows violation under miri. However, miri still flags the same violation because&mut selfis still a single opaque borrow — inlining the async block alone doesn't let miri split the disjoint field borrows across the.awaityield point.Comet CI reproduces this reliably: https://github.com/apache/datafusion-comet/actions/runs/24518967597/job/71671004017?pr=3916
What changes are included in this PR?
Change
PushDecoderStreamState::transitionto takeselfby value instead of&mut self. With&mut self, the generated future stores a mutable reference, and whenunfoldpins and polls it, miri sees the&mut selfas a single opaque borrow that conflicts across the.awaityield point. With ownedself, the future owns the state directly — no reference means no Stacked Borrows conflict. The struct fields are all heap-allocated or reference-counted, so the move is just pointer-sized copies, not a deep copy.Are these changes tested?
Existing tests cover this code path. The fix is validated by miri passing in CI (the same test that currently fails:
test_nested_types_extract_missing_struct_names_missing_field). We'll run Comet CI against this branch first to confirm the miri violation is resolved before merging.Are there any user-facing changes?
No.