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fix: Dispose record batches exported through the C stream interface - #483
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adamreeve merged 2 commits intoOct 22, 2026
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CArrowArrayStreamExporter and CArrowDeviceArrayStreamExporter read each batch from the managed stream, export it and then drop it without disposing it. The exported array holds its own references to the buffers, so when the consumer releases it only those references go away; the batch's references are left for the finalizer, which in a NativeAOT library may never run. The exported array now takes ownership of the batch: the ExportedAllocationOwner disposes it when the array is released, after it has unpinned the exported buffers. Exporting a batch directly with ExportRecordBatch is unchanged and still leaves the batch to the caller. Closes apache#464.
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This looks good to me thanks @ump45nose, I just have one testing suggestion.
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This looks good to me thanks @ump45nose
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What's Changed
CArrowArrayStreamExporter.GetNextandCArrowDeviceArrayStreamExporter.GetNextread a batch from the managed stream, export it and never dispose it. The exported array takes its own references to the buffers, so releasing it on the consumer side doesn't free the batch's references, and withNativeMemoryAllocatorthe memory is only reclaimed by the finalizer.This follows the third option from the issue: the exported array takes ownership of the batch.
ExportedAllocationOwnergetsTakeOwnership(IDisposable). Owned objects are disposed inDispose, after the exported buffers have been unpinned and their shared handles released, so memory managers that throw when disposed while pinned are not affected. This also covers buffers exported by pinning rather than through a shared handle.CArrowArrayExporterandCArrowDeviceArrayExporterget internalExportRecordBatchoverloads with atransferOwnershipflag. The stream exporters passtrue, so a batch is disposed when the consumer releases the exported array (or right away if the export fails). The publicExportRecordBatchmethods still leave the batch to the caller.Batches returned by an
IArrowArrayStreamare owned by the caller, so streams that keep using a batch after handing it out would now see it disposed once the consumer releases it.Tests:
ExportedArrayStreamDisposesBatchesOnReleaseandExportedDeviceStreamDisposesBatchesOnReleaseexport a stream whose batch is built withTestMemoryAllocator, import it again, and check that disposing the imported batch returns every rented buffer. Both fail onmain(buffers stay rented). The fullApache.Arrow.Testssuite passes on net8.0 locally (the pythonnet tests were skipped since Python isn't set up here).This PR was prepared with AI assistance.
Closes #464.