Prevent duplicate fairway areas In principal, there can be only one or no fairway area at each point on the map. Since polygons from real data will often be topologically inexact, just disallow equal geometries. This will also help to avoid importing duplicates with concurrent imports, once the history of fairway dimensions will be preserved.

CREATE CONSTRAINT TRIGGER fairway_dimensions_area_unique
    AFTER INSERT OR UPDATE OF area, staging_done
    ON waterway.fairway_dimensions
    FOR EACH ROW EXECUTE FUNCTION prevent_st_equals('area', 'staging_done');