A method and system for optimizing the execution of database statement is described. An aspect is related to providing a framework for the creation, association, and use of optimizer-related functions to calculate the cost of execution plans involving non-native database entities. Examples of these optimizer-related functions include selectivity, statistics, and costs functions. Another aspect is related to the optimization of database statements having non-boolean predicates. Yet another aspect is related to the determination and use of different granularity levels of information for submitting database statement predicates to optimizer-related functions. Optimizer-related functions can also be defined for system-supplied objects and entities.