Identifying Expensive PostgreSQL queries

query.sql

select substr(query, 0, 250), calls, 
    to_char(total_time/(60*60), '999,999,9999,999') as "Cumulative Time (hrs)", rows, 
    to_char(total_time/calls, '999.999') as per_call_ms 
  from pg_stat_statements 
  order by total_time desc 
  limit 12;

reset.sql

select pg_stat_statements_reset()

results.sql

                                 query                                         |    calls    | Cumulative Time (hrs) |    rows    | per_call_ms
-------------------------------------------------------------------------------+-------------+-----------------------+------------+-------------
 SELECT  "posts".* FROM "posts"  WHERE "posts"."crush_id" = ? LIMIT ?          |   256078900 |          1510,418     |   35940202 |   21.234
 UPDATE "posts" SET "state" = ?, "updated_at" = ? WHERE "posts"."id" = ?       |    48610033 |          1086,287     |   48610033 |   80.449
 etc... etc...
(12 rows)

to_char(total_time/(60*60), '999,999,9999,999') as "Cumulative Time (hrs)", rows, 

Total_time is in milliseconds, so to convert it to hours you should divide it by 1000.