Vacuuming and template0

[Alexander Stanier]

We vacuum our live database every night. Recently we then got a message
saying that we should vacuum "template1", "postgres" and "mp_base" or
the server would shut down. I now understand this is necessary to guard
against transaction wrap around and we did the full vacuum on these
databases straight away. The message has now gone away. We did not,
however, vacuum template0 and I notice that the age on this database is
now negative:

mp_live=# select datname, datvacuumxid, datfrozenxid, age(datfrozenxid)
from pg_database;
datname | datvacuumxid | datfrozenxid | age
-----------+--------------+--------------+-------------
postgres | 2140511881 | 1070040079 | 1078428152
mp_live | 2140510678 | 1066768855 | 1081699376
template1 | 2140511881 | 1070047126 | 1078421105
template0 | 499 | 499 | -2146499564
mp_base | 2140511881 | 1070049511 | 1078418720
(5 rows)

Should we attempt to vacuum template0? I read a note somewhere saying
that you can't vacuum template0 and don't need to. Is this correct?

Are there any consequences of the XID for template0 wrapping round and
the "age" becoming negative?

The system seems to be running normally. We are running PostgreSQL
8.1.11 on Redhat 5.1.

Thank you in advance for any advice.

Regards,
--
Alex Stanier

E-Government Solutions Ltd
Email: ***@egsgroup.com
www.egsgroup.com



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[Tom Lane]

Post by Alexander Stanier
Should we attempt to vacuum template0? I read a note somewhere saying
that you can't vacuum template0 and don't need to. Is this correct?

No; yes. template0 was frozen when it was made.

regards, tom lane