Re: which work memory parameter is used for what?

On Wed, Nov 9, 2016 at 7:54 AM, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>
wrote:

> On 11/08/2016 06:45 PM, Andreas Joseph Krogh wrote:
> > På onsdag 09. november 2016 kl. 03:02:54, skrev John R Pierce
> >
> >
> > https://www.postgresql.org/docs/current/static/runtime-
> config-resource.html
> >
> >
> > maintenance_work_mem is used by vacuum and create index operations
> > (including implicit index creation such as add foreign key).
> >
> >
> > There is no such thing in PG.
>
> Can you be more specific as;
>
> https://www.postgresql.org/docs/9.5/static/runtime-
> config-resource.html#GUC-MAINTENANCE-WORK-MEM
>
>
​I suppose that "
ALTER TABLE ADD FOREIGN KEY
​" uses maintenance_work_mem while executing the query necessary to confirm
that for every distinct value in the new foreign key there exists a
corresponding primary key. The PK already has an associated index because
of an implementation detail enforcing uniqueness. The foreign key has no
need for such an artifact.

David J.