gabotechs opened a new pull request, #22010:
URL: https://github.com/apache/datafusion/pull/22010
๐Don't look yet, still experimenting
## Which issue does this PR close?
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- Closes #.
## Rationale for this change
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Why are you proposing this change? If this is already explained clearly in
the issue then this section is not needed.
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Today RepartitionExec emits one small batch per (input batch ร non-empty
output partition), then coalesces those small batches back into target-sized
ones on the consumer side. That means the channel layer (memory accounting,
gate, await suspensions) does work proportional to num_partitions per input
batch, even though each small batch only carries batch_size / num_partitions
rows. Moving the coalescing producer-side, before the gate, collapses the
channel traffic and reduces sensitivity to high output fanout.
## What changes are included in this PR?
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- A producer-side coalescer per output partition, shared across input tasks,
that runs before the channel's gate.
- The redundant consumer-side coalescer in PerPartitionStream is removed.
- BatchPartitioner is unchanged โ only the layer between the partitioner and
the channel.
## Are these changes tested?
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Yes, by existing tests
## Are there any user-facing changes?
No
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