Re: Add visibility map information to pg_freespace.

 - How about pageinspect?

  I proposed a simple representation format as a basis for
  discussion. Nevertheless, the VM pages has no more structure
  than a simple bit string. Given the VM info in pg_freespacemap,
  I've come in doubt of the necessity of vm_page_contnets() for
  the reason besides the orthogonality in the this extension's
  interface (which paid no attention before:-).

 - How about pgstattuple?

  It could even be said to be meaningful to add the number of
  not-all-visible pages or the ratio of it in the total pages..

   | postgres=# select * from pgstattuple('t');
   | -[ RECORD 1 ]----------------+---------
   | table_len                    | 88711168
   | tuple_count                  | 600001
   | tuple_len                    | 26400044
   | tuple_percent                | 29.76
   | dead_tuple_count             | 399999
   | dead_tuple_len               | 17599956
   | dead_tuple_percent           | 19.84
   | free_space                   | 33607960
   | free_percent                 | 37.88
   + not_all_visible_page_percent | 23.54

# This column name looks too long, though.