Sketch Aggregation Operators
The 5 sketch ops cover approximate-cardinality, quantile, frequency, set-membership, and entropy estimation. All use bounded data structures regardless of stream length.
| Op | Memory class | CPU tier |
|---|---|---|
bv.n_unique |
BoundedSketch (HLL) | Tier 2/3 |
bv.quantile |
BoundedSketch (DDSketch) | Tier 2/3 |
bv.top_k |
BoundedByConfig("k") | Tier 2 |
bv.bloom_member |
BoundedSketch (Bloom) | Tier 1 |
bv.entropy |
BoundedByConfig("max_categories") | Tier 2 |
Two of the five (n_unique, quantile) were renamed per ADR-002 for Polars-convention consistency.
See also
- Operator catalog index — full 53-op catalogue
- cost-class.md — per-op CPU tier metadata (Tier 1/2/3)
- Per-operator memory governance: V0-MEM-GOV-02 — every lifetime aggregation operator declares a finite per-entity memory ceiling at register-time
- Pipeline DSL compilation rules — how
bv.<op>(...)calls compile to JSON wire form