Сreate parallel aggregate

Hello, everyone!

I was trying to create a parallel aggregate with base_type parameter and
failed

postgres=# CREATE AGGREGATE ST_Extent_parallel (
sfunc = ST_CombineBBox,
combinefunc = ST_CombineBBox,
finalfunc = box2d,
stype = box3d,
basetype = geometry,
parallel = safe
);
ERROR: syntax error at or near "parallel"
LINE 7: parallel = safe

But everything is ok if I use arg_data_type:

postgres=# CREATE AGGREGATE ST_Extent_parallel(geometry) (
sfunc = ST_CombineBBox,
combinefunc = ST_CombineBBox,
finalfunc = box2d,
stype = box3d,
parallel = safe
);
CREATE AGGREGATE

Is that a bug or a feature?

--
Grigory Smolkin
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company