GiST

PostgreSQL Exclusion Constraints Block Overlapping Ranges

A unique constraint can reject two equal scalar values, but equality is too narrow for many scheduling and allocation rules. Two reservations can have different start and end timestamps while still occupying the same interval. PostgreSQL exclusion constraints express this kind of conflict directly in the database. An exclusion constraint compares pairs of rows with declared operators. A pair is rejected when every operator comparison in the constraint is true. This turns operators such as range overlap into enforceable cross-row rules without relying on a query followed by an insert.