fix: correct percentile_cont(DISTINCT) accumulation and sliding-window retract - #23913
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viirya wants to merge 1 commit into
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fix: correct percentile_cont(DISTINCT) accumulation and sliding-window retract#23913viirya wants to merge 1 commit into
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…w retract `DistinctPercentileContAccumulator` had two bugs: 1. Panic on every distinct query. `update_batch` forwarded all argument columns to `GenericDistinctBuffer::update_batch`, which asserts a single input array. `percentile_cont` always passes two columns (the value and the percentile literal), so any `percentile_cont(DISTINCT x, p)` panicked with "DistinctValuesBuffer::update_batch expects only a single input array". 2. Wrong results in sliding windows. The buffer was a plain `HashSet` with no per-value multiplicity, so `retract_batch` removed a value entirely when a single occurrence left the window frame, even if other rows in the frame still carried that value. Replace the shared set-based buffer with a per-accumulator `HashMap<Hashable, usize>` count map: `update_batch` reads only the value column and increments counts, `retract_batch` decrements and removes a key only at zero, and `state`/`merge_batch` serialize the distinct keys as a List (unchanged state shape). The other `GenericDistinctBuffer` users (count/sum/ median/variance distinct) are unaffected; only percentile_cont supports retract, so it is the sole accumulator that needed multiplicity tracking. Add regression coverage in aggregate.slt for the plain distinct aggregate and for the sliding-window duplicate-value retract case. Co-authored-by: Claude Code
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Which issue does this PR close?
Rationale for this change
DistinctPercentileContAccumulatorreused the shared set-basedGenericDistinctBuffer, which doesn't fit it: (1) the buffer asserts a single input column butpercentile_contpasses two (value + percentile), so everypercentile_cont(DISTINCT ...)panicked; (2) the buffer is a plainHashSetwith no multiplicity, so sliding-windowretract_batchdropped a value while duplicates were still in the frame.What changes are included in this PR?
HashMap<Hashable, usize>count map:update_batchreads only the value column and increments;retract_batchdecrements and removes a key only at zero;state/merge_batchkeep the same List state shape. OtherGenericDistinctBufferusers are untouched.aggregate.sltfor the plain distinct query and the sliding-window duplicate-retract case.Are these changes tested?
Yes — new regression tests; the full
aggregate.sltsuite passes.Are there any user-facing changes?
percentile_cont(DISTINCT ...)now works instead of panicking, and returns correct results in sliding windows.