more about pg_toast growth

I have more data about unchecked growth of pg_toast tables.  After
another day's worth of inserting and deleting, the table in question has
39504 tuples.  The pg_toast table has 234773 tuples, and 126697 are
marked as unused.  The sum(length(chunk_data)) from pg_toast is
433165242.  The sum(length(resp_body)) -- the actual data in the table
-- is much bigger: 921615964.  How is that possible?

In any case it is clear that the table is just growing again.  The file
increased from 420MB to 730MB overnight, without a corresponding
increase in tuples.

The free space map settings in postgresql.conf are commented out.

I'd be very interested to find out how the sum of the length of the
tuples can be much larger than both the sum of lengths from the toast
table and the actual size of the file.

Regards,
Jeffrey Baker