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

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