Apparatus, system, and method for performing fast approximate computation of statistics on query expressions

摘要

An apparatus, system, and method are disclosed for performing fast approximate computation of statistics on query expressions in order to improve query optimization within a database management system by accurately and quickly estimating the sizes of intermediate query results. This is accomplished by analyzing a query for join instruction and identifying a fact table and a dimension table within those join instructions. Then, frequency statistics corresponding to distinct values of within the fact table are retrieved from a catalog table. Those frequency statistics are used in combination with a full scan of the dimension table accurately and quickly estimate frequency statistics for an expected join between the fact table and dimension table. The estimated frequency statistics corresponding to the expected join may then be used in such operations as query optimization.