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 &&)
);
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[ 3.0 ms ] story [ 12.2 ms ] threadThe 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):
http://www.postgresql.org/docs/9.1/static/ddl-constraints.ht...