Hi, this may be a start:
-- This will make our day better :)
with base_query (tstmp) as (
select DATE_TRUNC('hour',timestamp) as tstmp
FROM record
WHERE
record.timestamp BETWEEN ( CURRENT_TIMESTAMP + INTERVAL '-7 day') and
(CURRENT_TIMESTAMP) -- this I don't understand
)
-- The following will make the same as your query
select count(*) as qt, tstmp as dfilter from base_query
-- And this adds the zero's
union
select 0 as qt, min(tstmp) + interval generate_series( 0, max(tstmp) -
min(tstmp) ) || ' hours' as dfilter
from base_query
where dfilter not in tstmp; -- Only for those who don't!
Don't forget to tell us how you ended up!