以 10 分钟的间隔获取时间序列

Question

I am generating one time-series from using below query.

SELECT date_trunc('min', dd):: TIMESTAMP WITHOUT TIME zone as time_ent 
FROM generate_series ( timestamp '2021-12-09 06:34:37' + ((DATE_PART('min', timestamp '2021-12-09 06:34:37')::integer % 2) || ' minutes') :: INTERVAL 
, '2021-12-10 06:34:37'::timestamp 
, '20 min'::interval) dd

and it will give me output like below.

2021-12-09 06:34:00.000
2021-12-09 06:54:00.000
2021-12-09 07:14:00.000
2021-12-09 07:34:00.000

but I need output like.

2021-12-09 06:40:00.000
2021-12-09 07:00:00.000
2021-12-09 07:20:00.000
2021-12-09 07:40:00.000

currently, the time series hours depend upon the timestamp that I pass. in above it gives me mins like 34,54,14...but I want the mins like 40,00,20...it should not depend on the time I passed in query. I tried with timestamp '2021-12-09 06:34:37' + ((DATE_PART('min', timestamp '2021-12-09 06:34:37')::integer % 2) || ' minutes'):: INTERVAL but not any success.

Answer 1

Based on your description, I assumed that you want to create a series of timestamps for 00, 20, 40 minute at each hour until the next day.

select * 
from (
    select date_trunc('hour', current_timestamp) + i * interval '20 minutes' as ts
    from generate_series(1, 24*3) as t(i)) t
where ts between current_timestamp and current_timestamp + interval '1 day'

The key idea here is to truncate the current_timestamp to 00 minute first. This becomes the start of the series. Then filter out the generated timestamps outside the range you want. You may need to adjust the second argument of generate_series function, depending on your requirement.

Or you can just generate a series of timestamp like the following:

select *
from (
    select ts
    from generate_series(
      date_trunc('hour', current_timestamp),
      current_timestamp + interval '1 day',
      interval '20 minutes') as t(ts)) as t
where ts between current_timestamp and current_timestamp + interval '1 day'

Here, you still need to trunc your timestamp to hour first so the start of the series at 00 minute.