Benchmark single-column GROUP BY: hash vs direct-indexed flat array - #22481
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Adds `GroupValuesFlatPrimitive`, a direct-indexing GroupValues implementation for integer-typed GROUP BY columns with bounded value ranges. Uses `value - min` to index directly into a flat array — no hashing, no collisions, O(1) lookup. Adds a benchmark (`single_group_by_primitive`) that directly compares hash-based `GroupValuesPrimitive` vs `GroupValuesFlatPrimitive` using the same `iter_batched_ref` methodology as the multi-column GROUP BY benchmark in apache#22322. Only `intern()` is timed; construction is in setup. Three experiments: 1. Group count sweep (10–100K groups, 1M rows) 2. Density sweep (10K groups, 10%–100% density) 3. Row count scaling (10K groups, 1M–10M rows) Closes benchmarking aspect of apache#19938. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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run benchmarks |
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🤖 Benchmark running (GKE) | trigger CPU Details (lscpu)Comparing benchmark-single-group-by-flat-primitive (c2c07a4) to b382ecd (merge-base) diff using: tpch File an issue against this benchmark runner |
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🤖 Benchmark running (GKE) | trigger CPU Details (lscpu)Comparing benchmark-single-group-by-flat-primitive (c2c07a4) to b382ecd (merge-base) diff using: clickbench_partitioned File an issue against this benchmark runner |
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🤖 Benchmark running (GKE) | trigger CPU Details (lscpu)Comparing benchmark-single-group-by-flat-primitive (c2c07a4) to b382ecd (merge-base) diff using: tpcds File an issue against this benchmark runner |
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🤖 Benchmark completed (GKE) | trigger Instance: CPU Details (lscpu)Details
Resource Usagetpch — base (merge-base)
tpch — branch
File an issue against this benchmark runner |
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🤖 Benchmark completed (GKE) | trigger Instance: CPU Details (lscpu)Details
Resource Usagetpcds — base (merge-base)
tpcds — branch
File an issue against this benchmark runner |
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🤖 Benchmark completed (GKE) | trigger Instance: CPU Details (lscpu)Details
Resource Usageclickbench_partitioned — base (merge-base)
clickbench_partitioned — branch
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| None => None, | ||
| }; | ||
| let mut split = self.values.split_off(n); | ||
| std::mem::swap(&mut self.values, &mut split); |
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I'm trying to replace this pattern (split_off + swap) with split_vec_min_alloc #22416 to avoid unnecessary allocations
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got it. Going to separate this PR into 1) benchmarks 2) optimization diffs (GroupValuesFlatPrimitive)... |
nathanb9
marked this pull request as draft
May 27, 2026 13:08
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Thank you for your contribution. Unfortunately, this pull request is stale because it has been open 60 days with no activity. Please remove the stale label or comment or this will be closed in 7 days. |
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Summary
GroupValuesFlatPrimitive, a direct-indexingGroupValuesimplementation for integer GROUP BY columns with bounded value ranges (no hashing, O(1) array lookup viavalue - min)single_group_by_primitive) comparing hash-basedGroupValuesPrimitivevsGroupValuesFlatPrimitivesingle_group_byandprimitivemodules public for benchmark accessBenchmark design
Uses the same
iter_batched_refmethodology as the multi-column GROUP BY benchmark in #22322:intern()calls are measuredblack_boxprevents dead-code eliminationThree experiments:
Local results (Apple Silicon, release mode,
iter_batched_ref)Related
ArrayMapinjoins/array_map.rs(perfect hash join, PR perfect hash join #19411)Test plan
cargo test -p datafusion-physical-plan --lib flat_primitive— 5 unit tests passcargo clippy -p datafusion-physical-plan --benches -- -D warnings— cleancargo bench -p datafusion-physical-plan --bench single_group_by_primitive— runs successfully🤖 Generated with Claude Code + reviewed by me 😃