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benchmark results : It seems like we are 25x faster for u16 bitmap based accumulators (or I am sleepy :) ) |
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I think we can do the same for 16 bit types, it is just 65_536 bytes 8192 if we use a bitmap. |
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Oh wait, you're already doing that :) |
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Query 0 in clickbench_extended dataset (which uses (Other queries are faster but I believe that is more around variance ) |
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cc : @neilconway , @alamb , @martin-g . Please take a look whenever you get a chance |
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run benchmarks |
alamb
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Apr 9, 2026
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This looks like a great idea. Thank you @coderfender
| harness = false | ||
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| [[bench]] | ||
| name = "count_distinct" |
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can you please add this benchmark as a separate PR (so we can use our standard benchmark runner to confirm the results)?
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🤖 Benchmark running (GKE) | trigger CPU Details (lscpu)Comparing optimize_count_distinct (93acd98) to 4b1901f (merge-base) diff using: tpch File an issue against this benchmark runner |
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🤖 Benchmark running (GKE) | trigger CPU Details (lscpu)Comparing optimize_count_distinct (93acd98) to 4b1901f (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 optimize_count_distinct (93acd98) to 4b1901f (merge-base) diff using: tpcds File an issue against this benchmark runner |
alamb
reviewed
Apr 9, 2026
| /// Uses 256 bytes to track all possible u8 values. | ||
| #[derive(Debug)] | ||
| pub struct BoolArray256DistinctCountAccumulator { | ||
| seen: Box<[bool; 256]>, |
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I think you can probably use a BooleanBuffer from Arrow to make this signifcantly faster (I think [bool uses a byte for each booelan) 🤔
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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
File an issue against this benchmark runner |
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Which issue does this PR close?
Remove hashset based accumulators for smaller int data types and use bitmaps. Follow up of : #21453
Rationale for this change
What changes are included in this PR?
Are these changes tested?
Are there any user-facing changes?