The EXTFNAPIV4_DESCRIBE_COL_DISTINCT_VALUES attribute describes the distinct values for a column. Used in a describe_column_set scenario.
a_v4_extfn_estimate
The estimated number of distinct values for a column. This property is valid only for table arguments.
The UDF can set this property if it knows how many distinct values a column can have in its result table. The server uses this information during the Optimization state.
On success, returns the sizeof(a_v4_extfn_estimate), if it sets the value, or:
Valid in: