WITH bgstats AS (
  SELECT checkpoints_timed,
         checkpoints_req,
         checkpoints_timed + checkpoints_req checkpoints,
         checkpoint_sync_time,
         checkpoint_write_time,
         buffers_checkpoint,
         buffers_clean,
         maxwritten_clean,
         buffers_backend,
         buffers_backend_fsync,
         buffers_alloc,
         buffers_checkpoint + buffers_clean + buffers_backend total_buffers,
         pg_postmaster_start_time() startup,
         stats_reset,
         round(extract('epoch' from now() - stats_reset)/60)::numeric min_since_reset,
         --round(extract('epoch' from age(now(), current_date))/60)::numeric min_since_reset,
         delay.setting::numeric bgwriter_delay,
         lru.setting::numeric bgwriter_lru_maxpages,
         ratio.setting::numeric bgwriter_lru_multiplier
    FROM pg_stat_bgwriter
    JOIN pg_settings lru   ON lru.name = 'bgwriter_lru_maxpages'
    JOIN pg_settings delay ON delay.name = 'bgwriter_delay'
    JOIN pg_settings ratio ON ratio.name = 'bgwriter_lru_multiplier'
)
SELECT round(100.0*checkpoints_req/checkpoints,1)                 forced_ratio,
       round(min_since_reset/checkpoints,2)                       min_between,
       round(checkpoint_write_time::numeric/(checkpoints*1000),2) write_time_avg,
       round(checkpoint_sync_time::numeric/(checkpoints*1000),2)  sync_time_avg,
       round(total_buffers/128.0,1)                               mb_total,
       round(buffers_checkpoint/(128.0*checkpoints),2)            mb_per_ckpt,
       round(buffers_checkpoint/(128.0*min_since_reset*60),2)     mbps_ckpt,
       round(buffers_clean/(128.0*min_since_reset*60),2)          mbps_bgw,
       round(buffers_backend/(128.0*min_since_reset*60),2)        mbps_sess,
       round(total_buffers/(128.0*min_since_reset*60),2)          mbps_total,
       round(100.0*buffers_checkpoint/total_buffers,1)            pct_ckpt,
       round(100.0*buffers_clean/total_buffers,1)                 pct_bgw,
       round(100.0*buffers_backend/total_buffers,1)               pct_sess,
       round(100.0*maxwritten_clean/(min_since_reset*60000/bgwriter_delay),2) bgw_halt_only_len,
       round(100.0*maxwritten_clean/(nullif(buffers_clean,0)/bgwriter_lru_maxpages),2)  bgw_halt_ratio,
       round(1.0*buffers_alloc/total_buffers,3)                   new_ratio,
       now()-pg_postmaster_start_time()                           uptime,
       *
  FROM bgstats;