LantaoJin commented on code in PR #51:
URL: https://github.com/apache/datafusion-java/pull/51#discussion_r3256649533
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native/src/lib.rs:
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@@ -152,6 +156,62 @@ pub extern "system" fn
Java_org_apache_datafusion_DataFrame_collectDataFrame<'lo
})
}
+/// Bridges DataFusion's async [`SendableRecordBatchStream`] to the synchronous
+/// [`RecordBatchReader`] interface that `FFI_ArrowArrayStream` (and therefore
+/// the Java `ArrowReader`) consumes. Each call to `next()` drives one
+/// `runtime().block_on(stream.next())`, so memory pressure stays bounded by
the
+/// executor pipeline plus a single in-flight batch.
+struct StreamingReader {
+ schema: SchemaRef,
+ stream: SendableRecordBatchStream,
+}
+
+impl Iterator for StreamingReader {
+ type Item = Result<RecordBatch, ArrowError>;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ runtime()
+ .block_on(self.stream.next())
Review Comment:
Done. The body is now wrapped in `catch_unwind` and any panic is surfaced as
`ArrowError::ExternalError` so Java sees a normal exception. Or do you think we
should call `process::abort()` here? @andygrove
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