Operator classes
An operator class is a group of functions that allow the secondary-access method to store and search for values of a particular data type. The query optimizer uses an operator class to determine if an index can process the query with the least cost. For more information about the query optimizer, see the HCL OneDB™ Performance Guide.
The operator-class functions fall into the following categories:
- Strategy functions
- The database server uses the strategy functions of a secondary-access method to help the query optimizer determine whether a specific index is applicable to a specific operation on a data type. The strategy functions are the operators that can appear in the filter of an SQL statement.
- Support functions
- The database server uses the support functions of a secondary-access method to build and access the index. End users do not call these functions directly. When an operator in the filter of a query matches one of the strategy functions, the secondary-access method uses the support functions to traverse the index and obtain the results.
Each secondary-access method has a default operator class associated with it. By default, the CREATE INDEX statement associates the default operator class with an index.
The database server stores information about operator classes in the sysopclasses system catalog table.