mi_integer mi_key_funcid(MI_AM_KEY_DESC *keyDesc,
   mi_integer keyNum)

keyDesc

points to the key descriptor.

keyNum

specifies the column number of the index-based key or 0 for a single-key index.

For the first (or only) key, pass 0 as keyNum. Increment keyNum by one for each subsequent key in a composite index.

A UDR returns the values that make up a functional index. For example, the following statement creates an index from the values that the box() function returns:

CREATE INDEX box_func_idx ON zones (box(x1,y1,x2,y2)) USING map_am;

Use the DataBlade API FastPath facility to obtain values for function-based index keys.

A positive integer identifies the function that creates the values in the keyNum position of a composite-key index.

A return value of 0 indicates that the specified keyNum contains column values and does not belong to a functional index.

A negative value indicates that the CREATE INDEX statement specifies an unknown function to create the key.

See the discussions of:

• Fastpath functions in the IBM Informix: DataBlade API Programmer's Guide, including functions mi_func_desc_by_typeid() and mi_routine_exec().
• CREATE INDEX in the IBM Informix: Guide to SQL Syntax, particularly functional index information.