bench(parquet): cover DELTA_BYTE_ARRAY large values in the arrow_writer benchmark - #10512
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bench(parquet): cover DELTA_BYTE_ARRAY large values in the arrow_writer benchmark#10512adriangb wants to merge 1 commit into
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…er benchmark No existing benchmark writes DELTA_BYTE_ARRAY through the writer: the arrow_writer property matrix varies writer version, compression, bloom filters, and CDC, all on the default encoding, and encoding.rs benches encoders in isolation. Add shared-prefix and distinct large-string batches (128 rows x 2 MiB, so a single value exceeds the default 1 MiB page limit) run under plain and delta_byte_array properties with the dictionary disabled. The delta-vs-plain gap on identical data separates inherent encoding cost from writer overhead in the byte-budget sub-batching regime. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Which issue does this PR close?
Rationale for this change
No existing benchmark writes
DELTA_BYTE_ARRAYthrough the writer: thearrow_writerproperty matrix varies writer version, compression, bloom filters, and CDC, all on the default encoding, andencoding.rsbenches encoders in isolation.That gap matters for the large-value write path specifically: the byte-budget sub-batching in
write_batch_internal(#9972) measures raw payload bytes, and page-boundary behavior interacts with the encoding's cross-value state (#10489, #10505). None of that is visible to any current benchmark. #10511 tracks whether making the byte budget encoded-size-aware is worthwhile; these benchmarks are the measurement for that question.What changes are included in this PR?
Two new batches and one new bench group in
parquet/benches/arrow_writer.rs:large_string_shared_prefix: 128 rows x 2 MiB, long common prefix with a short distinct suffix (the caseDELTA_BYTE_ARRAYexists for)large_string_distinct: same shape, values differing from byte 0 (the adversarial case, prefix length ~0)Values are sized so one value alone exceeds the default 1 MiB page limit, the regime of #10489. Each batch runs under
plainanddelta_byte_arrayproperties (dictionary disabled), so the delta-vs-plain gap on identical data separates inherent encoding cost from writer overhead.Results on an Apple M-series laptop, current
main:plaindelta_byte_arraylarge_string_shared_prefixlarge_string_distinctNote these numbers shift when #10505 lands, in both directions: shared-prefix delta gets slower in CPU time because the encoder starts doing real prefix comparisons instead of degenerating to per-page
PLAIN(while the output shrinks ~128x), and distinct delta gets faster from halving the page count. That sensitivity is the point of having the benchmark.Are these changes tested?
The change is itself a benchmark; it compiles and runs under
cargo bench -p parquet --bench arrow_writer.Are there any user-facing changes?
No.
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