CREATE FUNCTION "URX_PUBLIC"."__st_countagg_transfn"(agg agg_count, rast raster, nband integer, exclude_nodata_value boolean, sample_percent double precision) 
 RETURNS agg_count AS 
$BODY$
	DECLARE
		_count bigint;
		rtn_agg agg_count;
	BEGIN

		-- only process parameter args once
		IF agg IS NULL THEN
			rtn_agg.count := 0;

			IF nband < 1 THEN
				RAISE EXCEPTION 'Band index must be greater than zero (1-based)';
			ELSE
				rtn_agg.nband := nband;
			END IF;

			IF exclude_nodata_value IS FALSE THEN
				rtn_agg.exclude_nodata_value := FALSE;
			ELSE
				rtn_agg.exclude_nodata_value := TRUE;
			END IF;

			IF sample_percent < 0. OR sample_percent > 1. THEN
				RAISE EXCEPTION 'Sample percent must be between zero and one';
			ELSE
				rtn_agg.sample_percent := sample_percent;
			END IF;
		ELSE
			rtn_agg := agg;
		END IF;

		IF rast IS NOT NULL THEN
			IF rtn_agg.exclude_nodata_value IS FALSE THEN
				SELECT width * height INTO _count FROM "URX_PUBLIC".ST_Metadata(rast);
			ELSE
				SELECT count INTO _count FROM "URX_PUBLIC"._ST_summarystats(
					rast,
				 	rtn_agg.nband, rtn_agg.exclude_nodata_value,
					rtn_agg.sample_percent
				);
			END IF;
		END IF;

		rtn_agg.count := rtn_agg.count + _count;
		RETURN rtn_agg;
	END;
	$BODY$
 LANGUAGE 'plpgsql' IMMUTABLE;