fix(optimizer): recall-SLA-aware topk bind — CMS-heap when recall is loose (~60× cheaper) - #371
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The Fig-12 harness flagged a P95 cost-gap tail: BindCountSketchOnTopK
hard-bound every non-exact top-k to CountSketch (~250 KB wire state)
when a Count-Min-with-heap (~4 KB) answers approximate heavy-hitter
queries fine under a loose recall SLA — ~66x more expensive than
necessary.
Make the top-k binding recall-tier-aware and cost-aware:
* Loose recall (recall@k >= ~0.9, no signed/exact-rank need; the
common case) -> CMS-with-heap (cheap, one-sided over-estimate).
* Tight recall (exact rank / signed / two-sided) -> CountSketch-
with-heap (unbiased median-of-rows).
The tie-break among families that meet the SLA uses the existing
optimizer::cost::wire cost table — the same "min cost s.t. SLA" the
oracle uses; for a loose SLA both clear the bar so the cheaper CMS-heap
wins. The CMS-with-heap emit path is already servable end-to-end
(stage_config promotes with_heap to CountMinSketchWithHeap;
asap_tier_analysis maps it to FrequencyTopk(CmsWithHeap)).
No per-query recall field exists yet, so the tier is inferred from the
accuracy target (Exact -> Tight, else Loose); threading a real per-query
recall@k target is the follow-up. bind_workload_typed keeps its pinned-
family routing via the new apply_with_tier entry point (CountSketch pick
-> Tight, CMS-on-topk pick -> Loose), so contract-row mappings are
unchanged. The redundant bind_cms_with_heap_on_topk helper is removed.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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The Fig-12 harness found the optimizer hard-binds topk → CountSketch (~250 KB wire state) where a CMS-with-heap (~4 KB) answers approximate heavy-hitter queries fine under a loose recall SLA — ~60× more expensive than necessary (the harness P95 cost-gap tail).
Fix (
sketch_algebra/rules/bind_cms_topk.rs):BindCountSketchOnTopKis now recall-tier-aware — Loose →{CMS-heap, CountSketch}, Tight →{CountSketch}— with a cost-min tie-break over the SLA-meeting set (the same min-cost-s.t.-SLA the oracle uses). Loose-recall topk → CMS-heap; exact/tight → CountSketch (unbiased).bind_workload_typedroutes pinned picks via the newapply_with_tier.Cost: loose-recall topk drops 250,200 → 4,200 B/flush (~59.6×), from the optimizer's own
wire.rstable.Recall source: no per-query recall field today (
AccuracyTargetis a frequency budget) → tier inferred conservatively (Exact→Tight, else Loose=cheap). Follow-up: thread a realrecall@k/signedtarget. Servability confirmed end-to-end (Cms{with_heap} → FrequencyTopk).Tests: 3 new (loose→CMS-heap, tight→CountSketch, cost-min pick) + fixed the old hard-bind test.
cargo build/test -p control_planegreen except one pre-existing unrelated failure (invalid_sketch_type_override_falls_back_to_default, verified on main via git stash).🤖 Generated with Claude Code