The combination of postgres's range types[1] and exclusion constraints[2] allow you to do this safely. My 'primary key' constraints look something like: AL

The combination of postgres's range types[1] and exclusion constraints[2] allow you to do this safely. My 'primary key' constraints look something like: ALTER TABLE foo ADD CONSTRAINT temporal_pk EXCLUDE USING GIST ( identity_id WITH =, valid_range WITH && ); It'd be nice if temporal foreign keys were supported too, where the existence of contiguous child rows through the valid_range of the parent was enforced, but I've had to use a trigger for that. [1]: http://www.postgresql.org/docs/9.3/static/rangetypes.html http://www.postgresql.org/docs/9.3/static/rangetypes.html [2]: http://www.postgresql.org/docs/9.3/static/ddl-constraints.html#DDL-CONSTRAINTS-EXCLUSION http://www.postgresql.org/docs/9.3/static/ddl-constraints.ht...