GH-10676: Fix IPC StreamReader projected schema - #10677
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Jefffrey merged 1 commit intoAug 15, 2026
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When a projection is set, StreamReader::schema() returned the full stream schema while the batches it produces carry the projected schema, breaking the RecordBatchReader contract. Return the projected schema that try_new already computes, mirroring the FileReader fix in apache#10627. Assisted-by: Cursor (Opus 5)
Rich-T-kid
approved these changes
Aug 13, 2026
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| match &self.projection { | ||
| Some((_, projected_schema)) => projected_schema.clone(), | ||
| None => self.schema.clone(), | ||
| } |
Jefffrey
approved these changes
Aug 14, 2026
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|
thanks @codeAnqiang-ma & @Rich-T-kid |
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Which issue does this PR close?
Rationale for this change
With a projection set,
StreamReaderyields batches with the projected schema, butStreamReader::schema()and itsRecordBatchReader::schema()impl return the full stream schema. Same as #10382 (csv) and #10613 (ipc file reader); #10627 fixedFileReader,StreamReaderwas the remaining case.What changes are included in this PR?
StreamReader::try_newalready computes as aSchemaRefand return it fromStreamReader::schema(); theRecordBatchReaderimpl delegates to it, asFileReaderdoes.test_file_reader_projected_schema_matches_batch_schema.Are these changes tested?
Yes, the new test fails before this change (14 column stream schema vs 3 column batch schema) and passes after. I ran:
cargo test -p arrow-ipc(143 passed) and--all-features(148 passed)cargo clippy -p arrow-ipc --all-targets --all-features -- -D warningscargo fmt --all -- --checkI did not run the full workspace suite; outside
arrow-ipceveryStreamReader::try_newcall site passesNone, which is unaffected.Are there any user-facing changes?
Yes. A projected IPC
StreamReadernow reports the same schema as the batches it produces. No public API signature changes.AI assistance: an AI agent found this by auditing the remaining
RecordBatchReaderimpls after #10613 and drafted the fix and its test; I reviewed every line and ran the reproduction and the checks above locally.