DB Wiki

The following SQL code displays the thresholds for when Autovacuum will clean up dead rows.
Dead rows occur in postgres when records are updated or deleted.

SELECT relname, n_live_tup, n_dead_tup, 
       FLOOR(current_setting('autovacuum_vacuum_threshold')::INTEGER + 
	    (current_setting('autovacuum_vacuum_scale_factor')::NUMERIC * 
	    (n_live_tup))) AS "Autovacuum Threshold",
       round(n_dead_tup / FLOOR(current_setting('autovacuum_vacuum_threshold')::INTEGER + 
	                       (current_setting('autovacuum_vacuum_scale_factor')::NUMERIC * 
		               (n_live_tup)))*100,2) AS "Percentage",
       last_vacuum, last_autovacuum 
FROM pg_stat_user_tables
WHERE n_live_tup > 0
ORDER BY 5 DESC LIMIT 10;