pg_stat_statement mean query

mean_query_check.sql

SELECT
  pg_stat_statements.query as query,
  round(pg_stat_statements.total_exec_time::numeric, 2) AS total_time,
  pg_stat_statements.calls,
  round(pg_stat_statements.mean_exec_time::numeric, 2) AS mean,
  round((100 * pg_stat_statements.total_exec_time /
  sum(pg_stat_statements.total_exec_time::numeric) OVER ())::numeric, 2) AS percentage_cpu,
  round((100 * pg_stat_statements.calls /
  sum(pg_stat_statements.calls::numeric) OVER ())::numeric, 2) AS percentage_calls,
  pg_user.usename as username,
  pg_database.datname as database
FROM
  pg_stat_statements
JOIN
  pg_database ON pg_database.oid = pg_stat_statements.dbid
JOIN
  pg_user ON pg_stat_statements.userid = pg_user.usesysid
ORDER BY mean DESC LIMIT 20;