Expert Indexing in Oracle Database 11g: Maximum Performance for Your Database

Function-Based Indexes

Oracle Database lets you create function-based indexes to facilitate queries that use values returned by a function. You can actually use a function or an expression to create a function-based index. The advantage to using a function-based index is that the database will compute the value of the function (or expression) that involves one or more columns ahead of time and stores it in the index that you create on the function. Since queries can use the precomputed values of expressions by looking up the index rather than having to compute the values at runtime, performance will improve when using these indexes. Function-based indexes increase the probability of the database using the more efficient index range scan rather ...