optimize(parquet): Nested list batching child.write calls#10085
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mapleFU wants to merge 6 commits into
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optimize(parquet): Nested list batching child.write calls#10085mapleFU wants to merge 6 commits into
mapleFU wants to merge 6 commits into
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mapleFU
commented
Jun 6, 2026
| /// counting child-element starts to find and stamp slot boundaries. | ||
| /// | ||
| /// Scan backward because we don't know start offset before writing. | ||
| fn write_list_scan<O: OffsetSizeTrait>( |
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I previously want to remove the branch for write non-nested childs, however benchmark shows that adding a more branch will hurt the performance. So I split it to two functions.
| for rep in rep_levels.iter_mut().rev() { | ||
| // This can uses `==`, since list write is recursive and the child is written | ||
| // before the parent. | ||
| if *rep <= ctx.rep_level { |
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I still use <= because benchmark shows no performance enhancement between <= and ==, so just uses <=
| // before the parent. | ||
| if *rep <= ctx.rep_level { | ||
| seen += 1; | ||
| if seen == next_stamp_at { |
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Maybe we can SIMD this in the future, this is not cirtical in this branch. Or we can "batching" if list offsets is large. E.g. checking not one-by-one, and just batch by batch
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Pull request overview
This PR optimizes Parquet level generation for nested Arrow List types by batching child.write(...) calls and applying repetition-level backfilling in larger chunks, reducing recursive write-call overhead for deeply nested list structures.
Changes:
- Split list writing into two specialized hot paths: an offsets-based “direct” backfill for last-level list children and a backward-scan backfill for nested repetition cases
- Extracted a shared run-classification loop (
write_list_impl) to batch null/empty/non-empty runs while keeping monomorphized backfill strategies
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mapleFU
commented
Jun 6, 2026
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|
run benchmark arrow_writer |
|
🤖 Arrow criterion benchmark running (GKE) | trigger CPU Details (lscpu)Comparing nested-list-optimize-write (0d16db7) to c3e0684 (merge-base) diff File an issue against this benchmark runner |
|
🤖 Arrow criterion benchmark completed (GKE) | trigger Instance: CPU Details (lscpu)Details
Resource Usagebase (merge-base)
branch
File an issue against this benchmark runner |
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Which issue does this PR close?
Rationale for this change
Optimize nested list call recursive write counts.
What changes are included in this PR?
Separate list write function to direct-by-offsets and by backward scan
Are these changes tested?
Covered by existing
Are there any user-facing changes?
No