-- A patch/switch port can be registered before the wall-outlet label is known.
ALTER TABLE locations_wall_outlets
    ALTER COLUMN outlet_number DROP NOT NULL;

ALTER TABLE locations_wall_outlets
    ADD COLUMN IF NOT EXISTS customer_id INTEGER
    REFERENCES customers(id) ON DELETE SET NULL;

CREATE INDEX IF NOT EXISTS idx_wall_outlets_customer_id
    ON locations_wall_outlets(customer_id)
    WHERE deleted_at IS NULL;