On Jan 6, 2018, at 12:11 PM, Corey Taylor <corey.taylor.fl@xxxxxxxxx> wrote: > Is it possible for an index to not exist on those columns? > > https://www.postgresql.org/docs/current/static/ddl-constraints.html#DDL-CONSTRAINTS-FK > > "A foreign key must reference columns that either are a primary key or form a unique constraint. This means that the referenced columns always have an index (the one underlying the primary key or unique constraint); so checks on whether a referencing row has a match will be efficient." One should also remember that the foreign key itself should usually be indexed, lest a delete on the referenced table require a table scan on the referencing table. -- Scott Ribe https://www.linkedin.com/in/scottribe/ (303) 722-0567
