Percentiles on end_to_end_time using postgres 9.2

gistfile1.sql

with percentiles1 as
	(select prison_name, end_to_end_time, cume_dist() over (partition by prison_name order by end_to_end_time) as percentile
	from visit_metrics_entries where processed_at is not null)
, top_percentiles1 as
	(select prison_name, end_to_end_time, rank() over (partition by prison_name order by end_to_end_time) as rank1
	from percentiles1 where percentile >= 0.95)
select prison_name, end_to_end_time from top_percentiles1 where rank1 = 1