Strategy and support functions of a secondary access method

Informix® 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.

If an index exists and the operator in the filter matches one of the strategy functions in the operator class, the optimizer considers whether to use the index for the query.

Informix uses the support functions of a secondary-access method to build and access the index. These functions are not called directly by end users. When an operator in the query filter matches one of the strategy functions, the secondary-access method uses the support functions to traverse the index and obtain the results. Identification of the actual support functions is left to the secondary-access method.


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