Using pg_stat_statements

CREATE EXTENSION pg_stat_statements;

shared_preload_libraries          = 'pg_stat_statements'
pg_stat_statements.max            = 10000
pg_stat_statements.track          = all
pg_stat_statements.track_planning = on

SELECT queryid, calls, total_exec_time, mean_exec_time, rows, query
  FROM pg_stat_statements ORDER BY total_exec_time DESC LIMIT 20;

SELECT mean_exec_time, calls, query
  FROM pg_stat_statements
 WHERE calls > 50 ORDER BY mean_exec_time DESC LIMIT 20;

SELECT calls, total_exec_time, query FROM pg_stat_statements
 ORDER BY calls DESC LIMIT 20;

SELECT query, shared_blks_read, shared_blks_hit,
       temp_blks_read, temp_blks_written
  FROM pg_stat_statements ORDER BY shared_blks_read DESC LIMIT 20;

SELECT pg_stat_statements_reset();