"Sometimes a table's usage pattern involves much more updates than
inserts, which gradually uses more and more unused space that is never
used again by postgres, and plain autovacuuming doesn't return it to the
OS."
Can you expound on that? I thought that was exactly what autovacuum did for old versions of rows whether dead because of delete or update, so I am surprised by this statement. I thought vacuum full was only ever needed if storage space is an issue and the table is not expect to quickly re-expand to current size on disk from new churn of tuples.