strange message on console

[Marco Maggesi <maggesi@math.unifi.it>]

Hello!

I have a DS10 with debian potato.  Each morning I find
plenty of this strange messages on the console:

  DEBUG: --Relation pg_tables--
  DEBUG: Pages 0: Changed 0, Reapped 0, Empty 0, New 0; Tup 0: Vac 0,
    Keep/VTL 0/0, Crash 0, UnUsed 0, MinLen 0, MaxLen 0; Re-using:
    Free/Avail. Space 0/0; EndEmpty/Avail. Pages 0/0. Elapsed 0/0 sec.
  DEBUG:  --Relation pg_indexes--
  DEBUG: Pages 0: Changed 0, Reapped 0, Empty 0, New 0; Tup 0: Vac 0,
    Keep/VTL 0/0, Crash 0, UnUsed 0, MinLen 0, MaxLen 0; Re-using:
    Free/Avail. Space 0/0; EndEmpty/Avail. Pages 0/0. Elapsed 0/0 sec.

No one of this messages is registered in the log files
`/var/log/*'.  Everything seems to work perfectly but I
would like to understand what's going on.  Any help
appreciated.  Thanks

MM