Function (trigger) to insert rows based on interval and duration - postgresql

Question

I have a schedule table, like so:
ScheduleId::uuid | Start::timestamptz(now()) | SlotSize::int(minutes) | Interval::int(days)
and a slot table like so:
SlotId::uuid | ScheduleId::uuid | Start::timestamptz | End::timestamptz
I want to automatically insert slots, based on a trigger on the schedule table.
So far I have:
create
trigger create_slots after insert
on
schedule for each row execute procedure create_new_slots();
create or replace function create_new_slots()
returns trigger
language plpgsql
as $function$
begin
-- in a loop determine how many slots there are, then insert each one
insert into slot
select
uuid_generate_v4(),
new."ScheduleId",
start, -- need to determine the start time of each instance of slot
end -- need to determine the end time of each instance of slot
-- end loop
end return new;
end $function$
I need to somehow put this into a cursor and calculate the number of slots and the start and end times each slot.
I am using PostgreSQL 10
Any help is appreciated!

Answer 1

OK so what I needed, it seems, was to generate a series based on the [Start] time (rounded to the hour), the end time (which is the [Start] time + the [PlanningHorizon] in days) and the [SlotSize]. Then loop through this series and insert each time slot into my [Slot] table:
CREATE OR REPLACE FUNCTION create_new_slots()
RETURNS trigger
LANGUAGE plpgsql
AS $function$
declare
slot timestamptz;
begin
for slot in select generate_series(
date_trunc('hour', new."Start")::timestamptz,
(new."Start" + interval '1' day * new."PlanningHorizon")::timestamptz,
new."SlotSize" * '1 minutes'::interval)
loop
insert into slot select uuid_generate_v4(), new."ScheduleId", slot, slot + new."SlotSize" * '1 minutes'::interval;
end loop;
return NEW;
end
$function$