[PR] GH-49285: [Python] Add `buffer` parameter to `RecordBatch.serialize()` [arrow]

["rustyconover (via GitHub)" <gi...@apache.org>]

rustyconover opened a new pull request, #49286:
URL: https://github.com/apache/arrow/pull/49286

   ### Rationale for this change
   
   Addresses https://github.com/apache/arrow/issues/49285
   
   When serializing many `RecordBatch` objects in a hot loop (e.g. streaming IPC to a socket, writing to shared memory), `RecordBatch.serialize()` allocates a new buffer on every call. This creates unnecessary allocation pressure when the caller already knows the required size and could reuse a single buffer across calls.
   
   ### What changes are included in this PR?
   
   Add an optional `buffer` parameter to `RecordBatch.serialize()`. When provided, the method serializes directly into the pre-allocated buffer instead of allocating a new one, and returns a zero-copy slice with the exact serialized size.
   
   Changes:
   - **`pyarrow/includes/libarrow.pxd`** — Add Cython declarations for `GetRecordBatchSize(batch, options, &size)` and `SerializeRecordBatch(batch, options, out)` overloads
   - **`pyarrow/table.pxi`** — Add `buffer` parameter to `RecordBatch.serialize()` with size validation and mutability checks
   - **`pyarrow/tests/test_ipc.py`** — Add tests for round-trip correctness, oversized buffers, exact-size buffers, too-small buffers, and immutable buffers
   
   ### Are these changes tested?
   
   Yes. New test `test_serialize_record_batch_to_buffer` covers all cases.
   
   ### Are there any user-facing changes?
   
   Yes. `RecordBatch.serialize()` now accepts an optional `buffer` keyword argument.
   
   * GitHub Issue: #49285


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Re: [PR] GH-49285: [Python] Add `buffer` parameter to `RecordBatch.serialize()` [arrow]

["github-actions[bot] (via GitHub)" <gi...@apache.org>]

github-actions[bot] commented on PR #49286:
URL: https://github.com/apache/arrow/pull/49286#issuecomment-3901931161

   :warning: GitHub issue #49285 **has been automatically assigned in GitHub** to PR creator.


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