fix(shm): split oversized batches so every frame fits its ring#37
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fix(shm): split oversized batches so every frame fits its ring#37mdashti wants to merge 1 commit into
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Operators emit offset slices of their accumulated state, and arrow-ipc writes a sliced variable-length array's whole values buffer, so one frame balloons to the state's size no matter the batch size. Compacting and halving on the oversized path bounds frames by the ring instead of asking embedders to size rings for their widest state.
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What
This PR splits an oversized batch at the shm send path so every encoded frame fits its ring.
Why
Operators emit offset slices of their accumulated state, and arrow-ipc writes a sliced variable-length array's whole values buffer, so one frame balloons to the state's size no matter the batch size. Small rings then fail wide GROUP BY and DISTINCT shapes with
MessageTooLarge, and the only workaround was sizing every ring for the widest state any query might carry.How
BatchChannelSendergainsmax_frame_bytes()(the ring's combined slot payload;Nonefor unbounded in-proc channels). When an encoded frame exceeds it, the send path compacts the rows withtake(dropping the shared buffers that cause the ballooning) and halves by rows until each frame fits, left-to-right so row order survives for sorted streams. The common case pays one length check. A single row larger than the ring still errors with the raise-the-knob message.Tests
Unit: an oversized sliced batch splits into under-cap frames that decode back to the identical rows in order; a single oversized row still errors. End-to-end: a wide
max(s)GROUP BY over 64KiB rings, whose raw partial-aggregate emits are ~10x the ring, matches the serial reference exactly.