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perf(query): fix O(n²) aggregation grouping (issue #31) - #71
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Issue: groups.iter().position() is O(g) per binding, making total complexity O(b × g) where b = bindings and g = groups. Fix: Use BTreeMap<Vec<Value>, Vec<Binding>> keyed by group key. - Complexity reduced from O(b × g) to O(b × log g) - Value already implements Ord, so Vec<Value> works as BTreeMap key
adityamukho
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Apr 3, 2026
…or Value Value::Ord's cross-variant fallthrough compared stack-frame pointer addresses, which is non-deterministic across call contexts and violates Rust's Ord contract (BTreeMap/BTreeSet require a consistent total order). This caused incorrect aggregation grouping (PR #71) and wrong OR/OrJoin deduplication (PR #68). Fix: use a stable u8 discriminant per variant for cross-variant ordering. Also fix the O(n²) Vec::contains deduplication in count-distinct and sum-distinct (issue #50, which PR #66 claimed to fix but did not): replace with BTreeSet, which is now safe because Value::Ord is a correct total order. Adds two regression tests: - value_ord_cross_variant_is_antisymmetric: proves the old code violated antisymmetry (cmp(a,b) must equal reverse(cmp(b,a))) - value_ord_cross_variant_is_stable: cross-variant ordering must depend only on the variant type, not the inner value Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This was referenced Apr 3, 2026
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Summary
Vec + position()scan withBTreeMap<Vec<Value>, Vec<Binding>>for groupingValuealready implementsOrd, soVec<Value>works as BTreeMap key