CREATE FUNCTION "URX_PUBLIC"."_add_raster_constraint_num_bands"(rastschema name, rasttable name, rastcolumn name) 
 RETURNS boolean AS 
$BODY$
	DECLARE
		fqtn text;
		cn name;
		sql text;
		attr int;
	BEGIN
		fqtn := '';
		IF length($1) > 0 THEN
			fqtn := quote_ident($1) || '.';
		END IF;
		fqtn := fqtn || quote_ident($2);

		cn := 'enforce_num_bands_' || $3;

		sql := 'SELECT "URX_PUBLIC".st_numbands(' || quote_ident($3)
			|| ') FROM ' || fqtn
			|| ' LIMIT 1';
		BEGIN
			EXECUTE sql INTO attr;
		EXCEPTION WHEN OTHERS THEN
			RAISE NOTICE 'Unable to get the number of bands of a sample raster: % (%)',
        SQLERRM, SQLSTATE;
			RETURN FALSE;
		END;

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