Re: Too frequent warnings for wraparound failure

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Tom Lane wrote:
> I wrote:
>
>>"Milen A. Radev" <milen(at)securax(dot)org> writes:
>>
>>>I review the log every morning. In the beginning I got "wraparound
>>>failure" warnings every third day. But from a week I got those warnings
>>>every day. Well we have one table in one database where there are a lot
>>>of inserts, but not that many - around 30-40 thousand per day.
>
>
>>Are you really doing half a billion transactions a day?
>
>
> I thought of another mechanism that wouldn't require such a preposterous
> load, only half a billion transactions since initdb. (How old is this
> installation, anyway, and which PG version?)

It's created on February 16 and is 7.4.7 on Debian GNU/Linux 3.0 (Woody)
(kernel 2.6.10).

>
> If you are creating new databases every day and you do it by cloning
> template0, then the new databases would come into existence with
> datfrozenxid equal to template0's. Once template0 is more than half a
> billion transactions old, you'd start seeing the warning.

No, we do not do anything like that. We imported all databases from a
backup created by using pg_dump.

>
> This is relatively harmless, but probably we should try to mask it.
> We could make CREATE DATABASE set datfrozenxid to current time when
> cloning a database that has datallowconn false, on the assumption that
> the source DB is entirely frozen and so there's nothing to vacuum yet.
>
> regards, tom lane

- --
Milen A. Radev
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