The EXTFNAPIV4_DESCRIBE_PARM_DISTINCT_VALUES attribute returns the number of distinct values. Used in a describe_parameter_get scenario.
a_v4_extfn_estimate
Returns the estimated number of distinct values across all invocations. valid only for scalar parameters.
If this information is available, the UDF returns the estimated number of distinct values with 100% confidence. If the information is not available, the UDF returns an estimate of 0 with 0% confidence.
On success, returns the sizeof(a_v4_extfn_estimate).
Sample _describe_extfn API function code fragment:
if( ctx->current_state >= EXTFNAPIV4_STATE_ANNOTATION ) { desc_est.value = 0.0; desc_est.confidence = 0.0; desc_rc = ctx->describe_parameter_get( ctx, 1, EXTFNAPIV4_DESCRIBE_PARM_DISTINCT_VALUES, &desc_est, sizeof(a_v4_extfn_estimate) ); }