Re: While only running pg_dump, postgresql performs writes inside base/ directory. How can we stop this?

- autovacuum is not off in the pre-snapshot (production) database. It
auto-runs every 2 weeks to avoid transaction ID wraparound.
- I tried modifying pgdump to have a more relaxed transaction isolation
(READ UNCOMMITTED) instead of the default (serializable) but this didn't
help.
thanks for the info.

On 10 December 2013 21:13, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:

> On Tue, Dec 10, 2013 at 12:43 AM, Spiros Ioannou <sivann(at)inaccess(dot)com>wrote:
>
>> Hi Jeff,
>> autovacuum is off on the DB running on the filesystem snapshot.
>>
>
>
> Which probably makes sense on the snapshot, but is it also off on the
> pre-snapshot database?
>
>
>> What "hint bits" do you suppose it is setting? It's running only one COPY
>> command for days. Do you have any suggestions to make it more "read only" ?
>>
>
>
> When a query sees a tuple that is still listed as part of an open
> transaction, it needs to figure out whether that transaction has now
> completed, and if so whether it committed or aborted. This can be quite a
> bit of work to do, so once complete it sets a hint bit locally to that
> tuple, so that the next visitor doesn't have to repeat the work. I don't
> believe that there is any way to turn this off, unless you want to run your
> own custom build of PostgreSQL.
>
> Cheers,
>
> Jeff
>