andygrove commented on code in PR #51:
URL: https://github.com/apache/datafusion-java/pull/51#discussion_r3262785555
##########
native/src/lib.rs:
##########
@@ -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:
Thanks @LantaoJin. I am actually not sure of the best approach. Let's go
ahead and merge this and we can keep iterating.
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