Performance bottleneck due to array manipulation

Hey,

i have a very long running stored procedure, due to array manipulation in a stored procedure. The following procedure takes 13 seconds to finish.

BEGIN
point_ids_older_than_one_hour := '{}';
object_ids_to_be_invalidated := '{}';

select ARRAY(SELECT
point_id
from ONLY
public.ims_point as p
where
p.timestamp < m_before_one_hour
)
into point_ids_older_than_one_hour ; -- this array has a size of 20k

select ARRAY(SELECT
object_id
from
public.ims_object_header h
WHERE
h.last_point_id= ANY(point_ids_older_than_one_hour)
)
into object_ids_to_be_invalidated; -- this array has a size of 100

-- current_last_point_ids will have a size of 100k
current_last_point_ids := ARRAY( SELECT
last_point_id
from
public.ims_object_header h
);
-- START OF PERFORMANCE BOTTLENECK
IF(array_length(current_last_point_ids, 1) > 0)
THEN
FOR i IN 0 .. array_upper(current_last_point_ids, 1)
LOOP
point_ids_older_than_one_hour = array_remove(point_ids_older_than_one_hour, current_last_point_ids[i]::bigint);
END LOOP;
END IF;
-- END OF PERFORMANCE BOTTLENECK
END;

The array manipulation part is the performance bottleneck. I am pretty sure, that there is a better way of doing this, however I couldn't find one.
What I have is two table, lets call them ims_point and ims_object_header. ims_object_header references some entries of ims_point in the column last_point_id.
Now I want to delete all entries from ims_point, where the timestamp is older than one hour. The currently being referenced ids of the table ims_object_header should be excluded from this deletion. Therefore I stored the ids in arrays and iterate over those arrays to exclude the referenced values from being deleted.

However, I not sure if using an array for an operation like this is the best approach.

Can anyone give me some advice how this could be enhanced.

Thanks in advance.