grouping by bucket size postgres

gistfile1.txt

https://stackoverflow.com/questions/22157718/postgres-group-by-timestamp-into-6-hourly-buckets

 select count(1), trunc(extract (minute from x) / 5) from generate_series(now() - '60 minute'::interval, now(), '1 minute'::interval) x group by trunc(extract (minute from x) / 5) order by 2 desc;
 count | trunc
-------+-------
     5 |    11
     5 |    10
     5 |     9
     5 |     8
     5 |     7
     5 |     6
     5 |     5
     5 |     4
     5 |     3
     6 |     2
     5 |     1
     5 |     0