Making predictions regarding evaluation of functions for a database environment

摘要

A prediction regarding one or more functions can be made for a database environment. In particular, a predication can be made with respect to values stored in at least one column of at least one table in a database, based on the evaluation of one or more functions for a subset of possible column values (i.e., resultant values derived from the evaluation of a subset of possible column values) without the need to calculate the function(s) for all of the actual entries in the column of the table(s). In effect, a functional predicate can be transformed (or translated) to a predicate that is dependent on the column values instead of the evaluation of one or more functions for the column values.

主权项

1. A computer-implemented method of determining cardinality of a database operation that depends on an evaluation of at least one function for column values of at least one column of at least one table of a database, the computer-implemented method comprises:
obtaining determined multiple ranges of possible column values for the at least one column of the at least one table; for each one of the multiple ranges of possible column values, obtaining a subset of possible column values in the range of column values as selected evaluation point values in the range; obtaining resultant functional values for the selected evaluation point values; identifying one or more ranges of the resultant functional values that are responsive to the database operation; identifying one or more corresponding column range values corresponding to the one or more resultant functional range values; and determining the cardinally of the database operation based on the identified corresponding column range values by at least:
transforming the cardinality of at least one functional predicate to cardinality of column values of the at least one column;determining the cardinality of the column values; andoutputting the cardinality of the column values as the cardinality of the database operation.