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perf!: remove shuffle buffer #5912

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Merged
westonpace merged 3 commits into from
Feb 10, 2026
Merged

perf!: remove shuffle buffer #5912

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74efab5
perf!: remove shuffle buffer
wkalt Feb 8, 2026
33b50fa
lint
wkalt Feb 8, 2026
8f12f82
make writes concurrent
wkalt Feb 9, 2026
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39 changes: 2 additions & 37 deletions rust/lance-index/src/vector/v3/shuffler.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,6 @@ use std::sync::Arc;
use arrow::{array::AsArray, compute::sort_to_indices};
use arrow_array::{RecordBatch, UInt32Array};
use arrow_schema::Schema;
use future::try_join_all;
use futures::prelude::*;
use lance_arrow::{RecordBatchExt, SchemaExt};
use lance_core::{
Expand Down Expand Up @@ -69,7 +68,6 @@ pub struct IvfShuffler {
num_partitions: usize,

// options
buffer_size: usize,
precomputed_shuffle_buffers: Option<Vec<String>>,
}

Expand All @@ -79,16 +77,10 @@ impl IvfShuffler {
object_store: Arc::new(ObjectStore::local()),
output_dir,
num_partitions,
buffer_size: 4096,
precomputed_shuffle_buffers: None,
}
}

pub fn with_buffer_size(mut self, buffer_size: usize) -> Self {
self.buffer_size = buffer_size;
self
}

pub fn with_precomputed_shuffle_buffers(
mut self,
precomputed_shuffle_buffers: Option<Vec<String>>,
Expand Down Expand Up @@ -163,43 +155,16 @@ impl Shuffler for IvfShuffler {
})
.buffered(get_num_compute_intensive_cpus());

// part_id: | 0 | 1 | 3 |
// partition_buffers: |[batch,batch,..]|[batch,batch,..]|[batch,batch,..]|
let mut partition_buffers = vec![Vec::new(); num_partitions];

let mut counter = 0;
let mut total_loss = 0.0;
while let Some(shuffled) = parallel_sort_stream.next().await {
let (shuffled, loss) = shuffled?;
total_loss += loss;

for (part_id, batches) in shuffled.into_iter().enumerate() {
let part_batches = &mut partition_buffers[part_id];
part_batches.extend(batches);
}

counter += 1;

// do flush
if counter % self.buffer_size == 0 {
let mut futs = vec![];
for (part_id, writer) in writers.iter_mut().enumerate() {
let batches = &partition_buffers[part_id];
if !batches.is_empty() {
partition_sizes[part_id] += batches.iter().map(|b| b.num_rows()).sum::<usize>();
futs.push(writer.write_batches(batches.iter()));
writers[part_id].write_batches(batches.iter()).await?;

@westonpace westonpace Feb 9, 2026

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We can do this in a follow-up but it might be nice to still do all the writes in parallel. E.g. keep the futs Vec. shuffled is a Vec and not any kind of stream / iterator so the data is all in memory already (I think the important point is getting rid of the if counter % self.buffer_size == 0)

let mut futs = vec![];
if !batches.is_empty() {
    futs.push(writers[part_id].write_batches(batches.iter()));
}
try_join_all(futs).await?;

@wkalt wkalt Feb 9, 2026

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thanks, updated

}
try_join_all(futs).await?;

partition_buffers.iter_mut().for_each(|b| b.clear());
}
}

// final flush
for (part_id, batches) in partition_buffers.into_iter().enumerate() {
let writer = &mut writers[part_id];
partition_sizes[part_id] += batches.iter().map(|b| b.num_rows()).sum::<usize>();
for batch in batches.iter() {
writer.write_batch(batch).await?;
}
}

Expand Down