Derived data dictionary for optimizing transformations of encoded data

Abstract

A database-management system evaluates a query that retrieves and transforms encoded symbols stored in a database. If the stored symbols assume a relatively small set of distinct values, the system initially performs the transformation on every value in the set. During execution of subsequent queries, rather than performing the transformation upon every stored symbol fetched from the database, the system merely returns the previously derived encoded transformation results that correspond to the decoded value of each fetched symbol. If the symbols stored in the database span a relatively large set of distinct values, the system does not initially perform the transformation upon every value in the set. Instead, the first time the system fetches a symbol that has a particular value, it saves that symbol's encoded transformation result and reuses that result the next time it fetches an encoded symbol with the same value.