foo.sql

select to_timestamp(start_time * 300) start_time_tz, to_timestamp((start_time + 1) * 300) end_time_tz, sum(amount) as volume, min(price) as low, max(price) as high, coalesce(lag(max(last_price)) over (order by start_time), max(first_price)) as first, max(last_price) as last
from (
  select date/300 as start_time, amount, price, first_value(price) over w as first_price, last_value(price) over w as last_price
  from trades
  where date/300 >= ((1367153251/300) - 120)
  window w as (partition by date/300 order by date rows between unbounded preceding and unbounded following)
) s
group by start_time
order by start_time desc;