Optimizing postgres row overlap constraints involving UUIDs and GIST

For various reasons all my tables have UUIDs as primary keys and I need to exclude duplicate rows where the combination of area_id, user_id, and finished_at started_at window.

The only way I can see to do this involves casting UUIDs to text inside the overlapping_allocations constraint below.
However this seems stupidly wasteful, am I missing a trick?

This is all running on Postgres 9.3.5 and there is freedom to enable other common extensions.

CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
CREATE EXTENSION IF NOT EXISTS "btree_gist";

CREATE TABLE areas(
    id uuid PRIMARY KEY default uuid_generate_v1(),
    name text NOT NULL UNIQUE,
    -- blah blah, lots of other fields
)

CREATE TABLE allocations(
    id uuid PRIMARY KEY default uuid_generate_v1(),
    area_id uuid references areas,
    user_id text NOT NULL,
    started_at timestamp with time zone NOT NULL,
    finished_at timestamp with time zone DEFAULT NULL,
    created_at timestamp with time zone default NOW(),
    CONSTRAINT valid_times CHECK (started_at < finished_at),
    CONSTRAINT overlapping_allocations EXCLUDE USING GIST (
        -- These two casts are horrid but GIST doesn't understand uuids
        -- see here https://stackoverflow.com/questions/22720130/how-to-use-uuid-with-postgresql-gist-index-type
        cast("area_id" AS text) WITH =,
        user_id WITH =,
        tstzrange(started_at, COALESCE(finished_at, 'infinity'::timestamptz) ) WITH &&
    )
);

As of Postgres 10 the btree_gist extension (in contrib) supports UUIDs, so if you add that extension first, you'll be able to create indexes and exclusion constraints without casting to text. Pre-10, casting to text is the way to go.

StackExchange Database Administrators Q#83604, answer score: 2