Optimization of query evaluation algorithms
ACM Transactions on Database Systems (TODS)
Optimizing the performance of a relational algebra database interface
Communications of the ACM
SIGMOD '75 Proceedings of the 1975 ACM SIGMOD international conference on Management of data
Access path selection in a relational database management system
SIGMOD '79 Proceedings of the 1979 ACM SIGMOD international conference on Management of data
Grounding FO and FO(ID) with bounds
Journal of Artificial Intelligence Research
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We present a statistic model which allows us to estimate the cardinality of queries and sub-queries expressed in Predicate Calculus language. In a first step, we deal with expressions formed only with an AND operator with n operands. We show how we can estimate recursively the cardinality of an expression with n operands in function of an expression of n-1 operands. The formulae giving the cardinalities are calculated under several hypotheses concerning the independence of criteria which determine sub-expressions, and those which define the relations. The parameters which must be known are : the cardinalities of the relations and of their projections on each argument; the probability for an element in the intersection of several projections of relations to be in a given projection of a relation (these parameters are called inter-relation quantified dependencies); the probability that several components of a tuple of a relation are equal; and the probability that the constants which appear in a query belong to the corresponding projections of the relations. In a second step, we extend the method to general expressions including the operators NOT and OR. Finally, we discuss the feasibility of the method.