Re: Update to 9.1.12

Viktor wrote:
> We are currently running PostgreSQL version 9.1.9-1~bpo60+1 (Debian Squeeze) and would like to update
> it to 9.1 9.1.12-0wheezy1.
>
> But there is one serious issue about this update:
>
> "
> E.3.2. Changes
>
>
>
>
> Fix VACUUM's tests to see whether it can update relfrozenxid (Andres Freund)
>
> In some cases VACUUM (either manual or autovacuum) could incorrectly advance a table's relfrozenxid
> value, allowing tuples to escape freezing, causing those rows to become invisible once 2^31
> transactions have elapsed. The probability of data loss is fairly low since multiple incorrect
> advancements would need to happen before actual loss occurs, but it's not zero. Users upgrading from
> releases 9.0.4 or 8.4.8 or earlier are not affected, but all later versions contain the bug.
>
> The issue can be ameliorated by, after upgrading, vacuuming all tables in all databases while having
> vacuum_freeze_table_age <http://www.postgresql.org/docs/9.1/static/runtime-config-client.html#GUC-
> VACUUM-FREEZE-TABLE-AGE> set to zero. This will fix any latent corruption but will not be able to fix
> all pre-existing data errors. However, an installation can be presumed safe after performing this
> vacuuming if it has executed fewer than 2^31 update transactions in its lifetime (check this with
> SELECT txid_current() < 2^31).
>
> "
>
> Please explain should I run VACUUM on all tables after the update if >
>
> postgres=# SELECT txid_current() < 2^31;
> ?column?
> ----------
> t
> (1 row)

Yes. That's what the release notes say.

One easy option is to run
PGOPTIONS='-o vacuum_freeze_table_age=0' vacuumdb

Yours,
Laurenz Albe