The hcp billing `_all` views built a range of buckets using the
`generate_series` function using the minimum value of the
`session_pending_time` column from the `wh_session_accumulating_fact`
table as the start time and `now()` as the end time. It then truncated
values in the series using the `date_trunc` function. This allowed the
generated series of buckets returned to vary and could result in one
additional bucket being included in the series depending on the current
time and the start time.
As an illustrative example, the `hourly_all` query used:
select date_trunc('hour',time)
from generate_series(
(select min(session_pending_time) -- start time
from wh_session_accumulating_fact),
now(),
'1 hour'::interval
) as time;
Substituting the start time with a hard coded value to show the issue:
-- Show current time, where the minutes portion is 55
select now();
now
-------------------------------
2023-05-22 14:55:40.567605+00
(1 row)
-- generate series with start time's minutes portion at 57
select date_trunc('hour',time)
from generate_series(
'2023-05-22 01:57:00'::timestamptz,
now(),
'1 hour'::interval
) as time;
date_trunc
------------------------
2023-05-22 01:00:00+00
2023-05-22 02:00:00+00
2023-05-22 03:00:00+00
2023-05-22 04:00:00+00
2023-05-22 05:00:00+00
2023-05-22 06:00:00+00
2023-05-22 07:00:00+00
2023-05-22 08:00:00+00
2023-05-22 09:00:00+00
2023-05-22 10:00:00+00
2023-05-22 11:00:00+00
2023-05-22 12:00:00+00
2023-05-22 13:00:00+00
(13 rows)
-- Wait a few minutes
select now();
now
------------------------------
2023-05-22 14:58:48.75287+00
(1 row)
-- Now run again and get an extra result, even though still
-- within the same hour
select date_trunc('hour',time)
from generate_series(
'2023-05-22 01:57:00'::timestamptz,
now(),
'1 hour'::interval
) as time;
date_trunc
------------------------
2023-05-22 01:00:00+00
2023-05-22 02:00:00+00
2023-05-22 03:00:00+00
2023-05-22 04:00:00+00
2023-05-22 05:00:00+00
2023-05-22 06:00:00+00
2023-05-22 07:00:00+00
2023-05-22 08:00:00+00
2023-05-22 09:00:00+00
2023-05-22 10:00:00+00
2023-05-22 11:00:00+00
2023-05-22 12:00:00+00
2023-05-22 13:00:00+00
2023-05-22 14:00:00+00
(14 rows)
To fix this, we call the `generate_series` function truncating the start
time argument to the bucket size:
-- Hourly
select bucket
from generate_series(
date_trunc('hour', select min(session_pending_time)
from wh_session_accumulating_fact)),
now(),
'1 hour'::interval
) as bucket;
-- Monthly
select bucket
from generate_series(
date_trunc('month', select min(session_pending_time)
from wh_session_accumulating_fact)),
now(),
'1 month'::interval
) as bucket;
Fixes: 41b1b5b4b7
Michael Gaffney
47ddd2e40a