I believe parent is referring essentially to the auto vacuum scale factor parameter (https://www.postgresql.org/docs/9.6/static/runtime-config-autovacuum.html#G

I believe parent is referring essentially to the auto vacuum scale factor parameter (https://www.postgresql.org/docs/9.6/static/runtime-config-autovacuum.html#GUC-AUTOVACUUM-VACUUM-SCALE-FACTOR https://www.postgresql.org/docs/9.6/static/runtime-config-au...) For a big table with frequent writes, the default is too much (20% dead tuples).