Using gist indices for exclusion constraints (added in pg 9.0) can be pretty useful also. The Postgres docs show a simple example that enforces the constraint

Using gist indices for exclusion constraints (added in pg 9.0) can be pretty useful also. The Postgres docs show a simple example that enforces the constraint "no two rows in the table contain overlapping circles" (&& is the overlaps operator for geometric types): CREATE TABLE circles ( c circle, EXCLUDE USING gist (c WITH &&) ); http://www.postgresql.org/docs/9.1/static/ddl-constraints.html#DDL-CONSTRAINTS-EXCLUSION http://www.postgresql.org/docs/9.1/static/ddl-constraints.ht...