On Wed, Nov 9, 2016 at 7:54 AM, Adrian Klaver <adrian.kla...@aklaver.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.
