Josh Berkus wrote:
>
> > You can see the current multixact value in pg_controldata output. Keep
> > timestamped values of that somewhere (a table?) so that you can measure
> > consumption rate. I don't think we provide SQL-level access to those
> > values.
>
> Bleh. Do we provide SQL-level access in 9.4? If not, I think that's a
> requirement before release.
Yeah, good idea. Want to propose a patch?
> >> Also: how do I check the multixact age of a table? There doesn't seem
> >> to be any data for this ...
> >
> > pg_class.relminmxid is the oldest multixact value that might be present
> > in a table.
>
> On every database I've tested, age(relminmxid) returns int_max. So this
> is apparently broken.
Hmm, are you sure it's INT_MAX and not 4244967297? Heikki reported
that: http://www.postgresql.org/message-id/52401AEA.9000608@vmware.com
The absolute value is not important; I think that's mostly harmless. I
don't think applying age() to a multixact value is meaningful, though;
that's only good for Xids.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
