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.
