Dandandan commented on code in PR #2359:
URL:
https://github.com/apache/datafusion-ballista/pull/2359#discussion_r3841785270
##########
ballista/core/src/execution_plans/sort_shuffle/writer.rs:
##########
@@ -1271,11 +1276,14 @@ fn compute_partition_indices(
hash_buffer,
)?;
- let mut out: Vec<Vec<u32>> = (0..num_partitions).map(|_|
Vec::new()).collect();
+ out.resize_with(num_partitions, Vec::new);
+ for rows in out.iter_mut() {
+ rows.clear();
+ }
for (row, &h) in hash_buffer.iter().enumerate() {
out[(h % num_partitions as u64) as usize].push(row as u32);
Review Comment:
This is also commonly a slow path, in DataFusion I went so far to replace it
with strength reduce https://github.com/apache/datafusion/pull/21900
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