9.2.1 & index-only scans : abnormal heap fetches after VACUUM FULL

How do we want to handle the case where VACUUM FULL clears the
visibility map, causing loss of index-only scans?
http://archives.postgresql.org/pgsql-performance/2012-11/msg00317.php

Do we document this behavior or add a TODO item?

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + It's impossible for everything to be true. +