Remove all but the latest n rows with group by

housekeeping.sql

-- Simply set the offset to the amount of rows you want to keep. An index of (id, date desc) will make this fast.


delete from some_table st
using (
  select distinct 
    x.id, 
    x.date 
  from some_table st1
  join lateral (
    select 
      id, date
    from some_table st2
    where st2.id = st1.id
    order by st2.date desc
    limit 1
    offset 1000
  ) x on true
) x2
where st.id = x2.id and st.date <= x2.date

housekeeping_window.sql

delete from some_table st
using (
  select 
    id, 
    date 
  from (
    select 
      id, 
      date, 
      row_number() over (
        partition by id 
        order by date desc
      )
    from some_table
  ) where row_number > 1000;
) x
where st.id = x.id and st.date = x.date