Normal limiting distributions for projection and semijoin sizes
SIAM Journal on Discrete Mathematics
An introduction to the analysis of algorithms
An introduction to the analysis of algorithms
Approximating block accesses in database organizations
Communications of the ACM
Analysis and performance of inverted data base structures
Communications of the ACM
A Cost Model for Clustered Object-Oriented Databases
VLDB '95 Proceedings of the 21th International Conference on Very Large Data Bases
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Yao's formula is one of the basic tools in any situation where one wants to estimate the number of blocks to be read in answer to some query. We show that such situations can be modelized by probabilistic urn models. This allows us to fully characterize the distribution probability of the number of selected blocks under uniformity assumptions, and to consider extensions to non-uniform block probabilities. We also obtain a computationnally efficient approximation of Yao's formula.