Optimization functions
Optimization functions help the query optimizer determine
the most efficient query plan for a particular SQL statement. These
optimization functions are as follows.
- Negator function
- Specifies the function to use for a NOT condition that involves a Boolean UDR
- Cost function
- Specifies the cost factor for execution of a particular UDR
- Selectivity function
- Specifies the percentage of rows for which a Boolean UDR is expected to return true
- Parallel UDR
- A UDR that can be run in parallel and therefore can be run in parallel queries
- Statistics function
- Creates distribution statistics for a UDT
The database server provides optimization functions for the built-in data types. You can write an optimization function on any UDT that is registered in the database. You cannot extend existing optimization for built-in types through optimization functions.
For more information about optimization functions, see Improve UDR performance.