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.
" 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.