Counting algorithm: search cost
Search cost is sensitive to predicate selectivity:
- 1: Computing all satisfied predicates
- d? ln(P)
- P is the avg number of predicates per dimension
- 2: Counting satisfied predicates
- Unitcount ? N ? sp ? p_avgmatch
- N is the number o subscriptions
- sp is the avg number of predicates per subscriptions
- p_avgmatch is a avg probability of a predicate to be satisfied