refactor: address review feedback on percentile_cont(DISTINCT) accumulator - #23946
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Follow-up to the DistinctPercentileContAccumulator fix, addressing post-merge review comments: - Use the fast foldhash RandomState for the `counts` map instead of the standard library's default SipHash, matching GenericDistinctBuffer. - Compute size() via estimate_memory_size, mirroring the other distinct accumulators. - Add a null-free fast path to update_batch and retract_batch that skips the per-element validity check when the input array has no nulls. - Add ORDER BY id to the sliding-window regression query in aggregate.slt so its output row order is deterministic. Co-authored-by: Claude Code
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Add a grouped percentile_cont(DISTINCT ...) regression test. A GROUP BY with target_partitions=4 forces two-phase (Partial + FinalPartitioned) aggregation, so the distinct accumulator's state() and merge_batch() paths run — the paths the previous whole-table regression queries did not reach (flagged by patch-coverage review on apache#23913). Duplicate values within each group also verify multiplicity is preserved across the per-partition merge. Co-authored-by: Claude Code
Per review discussion: if `retract_batch` is asked to remove a value not in the count map, the accumulator's state has diverged from the window frame and continuing would silently produce wrong results. Return an `internal_err!` instead of skipping, so the inconsistency surfaces rather than yielding a wrong answer. Co-authored-by: Claude Code
neilconway
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Jul 28, 2026
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Thanks for the quick turnaround! lgtm
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Thank you @neilconway for the reviews |
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #23946 +/- ##
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Coverage 80.69% 80.70%
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Files 1095 1095
Lines 372626 372542 -84
Branches 372626 372542 -84
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- Hits 300700 300651 -49
+ Misses 53978 53924 -54
- Partials 17948 17967 +19 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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Add a sliding-window percentile_cont(DISTINCT ...) regression over data containing a NULL positioned so that both the update_batch (NULL row enters the frame) and retract_batch (NULL row leaves the frame) code paths take the null_count() > 0 branch. Verified via temporary eprintln that both branches execute; the previous distinct-percentile tests used no NULLs and left those branches uncovered. Co-authored-by: Claude Code
This was referenced Jul 28, 2026
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Rationale for this change
Follow-up to post-merge review feedback from @neilconway on #23913.
What changes are included in this PR?
RandomStatefor the distinct-value count map instead of the standard library's default SipHash (the sharedGenericDistinctBufferalready does this; the merged fix regressed to SipHash on this hot path).estimate_memory_sizeinsize()instead of a hand-rolled capacity calculation.update_batch/retract_batch(skip per-element validity checks when the input has no nulls), mirroringGenericDistinctBuffer.ORDER BYto the sliding-window regression test so its row order is deterministic.Are these changes tested?
Yes — existing percentile unit tests and the full
aggregate.sltpass.Are there any user-facing changes?
No.