Request for improvement: Allow to push (t.o).id via GROUP BY ocd.o

Hello PostgreSQL-development,

something's stopping the planner from being able to deduce that (t.o).id is safe to push through a GROUP BY ocd.o

SELECT * FROM (
SELECT
sum( t.group_suma ) OVER( PARTITION BY t.id ) AS total_suma,
-- sum( t.group_suma ) OVER( PARTITION BY (t.o).id ) AS total_suma, -- For any WHERE this takes 2700ms
*
FROM (
SELECT
sum( ocd.item_cost ) AS group_cost,
sum( ocd.item_suma ) AS group_suma,
max( (ocd.ic).consumed ) AS consumed,
(ocd.ic).consumed_period,
ocd.o,
(ocd.o).id
FROM order_cost_details( tstzrange( '2019-04-01', '2019-05-01' ) ) ocd
GROUP BY ocd.o, (ocd.o).id, (ocd.ic).consumed_period
) t
) t
WHERE t.id = 6154 AND t.consumed_period @> '2019-04-01'::timestamptz -- This takes 2ms
-- WHERE (t.o).id = 6154 AND t.consumed_period @> '2019-04-01'::timestamptz -- This takes 2700ms

More info is here: https://stackoverflow.com/q/57003113/4632019

--
Best regards,
Eugen Konkov