CREATE FUNCTION "URX_PUBLIC"."_add_raster_constraint_blocksize"(rastschema name, rasttable name, rastcolumn name, axis text) 
 RETURNS boolean AS 
$BODY$
	DECLARE
		fqtn text;
		cn name;
		sql text;
		attrset integer[];
		attr integer;
	BEGIN
		IF lower($4) != 'width' AND lower($4) != 'height' THEN
			RAISE EXCEPTION 'axis must be either "width" or "height"';
			RETURN FALSE;
		END IF;

		fqtn := '';
		IF length($1) > 0 THEN
			fqtn := quote_ident($1) || '.';
		END IF;
		fqtn := fqtn || quote_ident($2);

		cn := 'enforce_' || $4 || '_' || $3;

		sql := 'SELECT st_' || $4 || '('
			|| quote_ident($3)
			|| ') FROM ' || fqtn
			|| ' GROUP BY 1 ORDER BY count(*) DESC';
		BEGIN
			attrset := ARRAY[]::integer[];
			FOR attr IN EXECUTE sql LOOP
				attrset := attrset || attr;
			END LOOP;
		EXCEPTION WHEN OTHERS THEN
			RAISE NOTICE 'Unable to get the % of a sample raster: % (%)',
        $4, SQLERRM, SQLSTATE;
			RETURN FALSE;
		END;

		sql := 'ALTER TABLE ' || fqtn
			|| ' ADD CONSTRAINT ' || quote_ident(cn)
			|| ' CHECK (st_' || $4 || '('
			|| quote_ident($3)
			|| ') IN (' || array_to_string(attrset, ',') || '))';
		RETURN  "URX_PUBLIC"._add_raster_constraint(cn, sql);
	END;
	$BODY$
 LANGUAGE 'plpgsql' VOLATILESTRICT ;