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FFI_RecordBatchStream was causing a memory leak #17190

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Merged
alamb merged 2 commits into from
Aug 19, 2025
Merged

FFI_RecordBatchStream was causing a memory leak #17190

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327f8bc
FFI_RecordBatchStream was causing a memory leak
timsaucer Aug 14, 2025
afcc677
Merge remote-tracking branch 'apache/main' into bugfix/drop-ffi-rbs-p…
alamb Aug 18, 2025
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16 changes: 16 additions & 0 deletions datafusion/ffi/src/record_batch_stream.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,9 @@ pub struct FFI_RecordBatchStream {
/// Return the schema of the record batch
pub schema: unsafe extern "C" fn(stream: &Self) -> WrappedSchema,

/// Release the memory of the private data when it is no longer being used.
pub release: unsafe extern "C" fn(arg: &mut Self),

/// Internal data. This is only to be accessed by the provider of the plan.
/// The foreign library should never attempt to access this data.
pub private_data: *mut c_void,
Expand All @@ -82,6 +85,7 @@ impl FFI_RecordBatchStream {
FFI_RecordBatchStream {
poll_next: poll_next_fn_wrapper,
schema: schema_fn_wrapper,
release: release_fn_wrapper,
private_data,
}
}
Expand All @@ -96,6 +100,12 @@ unsafe extern "C" fn schema_fn_wrapper(stream: &FFI_RecordBatchStream) -> Wrappe
(*stream).schema().into()
}

unsafe extern "C" fn release_fn_wrapper(provider: &mut FFI_RecordBatchStream) {
let private_data =
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@alamb alamb Aug 18, 2025

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I double checked that the private_data is actually a RecordBatchStreamPrivateData that is created with the constructor

datafusion/datafusion/ffi/src/record_batch_stream.rs

Lines 80 to 84 in 327f8bc

pub fn new(stream: SendableRecordBatchStream, runtime: Option<Handle>) -> Self {
let private_data = Box::into_raw(Box::new(RecordBatchStreamPrivateData {
rbs: stream,
runtime,
})) as *mut c_void;

Box::from_raw(provider.private_data as *mut RecordBatchStreamPrivateData);
drop(private_data);
}

fn record_batch_to_wrapped_array(
record_batch: RecordBatch,
) -> RResult<WrappedArray, RString> {
Expand Down Expand Up @@ -197,6 +207,12 @@ impl Stream for FFI_RecordBatchStream {
}
}

impl Drop for FFI_RecordBatchStream {
fn drop(&mut self) {
unsafe { (self.release)(self) }
}
}

#[cfg(test)]
mod tests {
use std::sync::Arc;
Expand Down