setup
{
  CREATE TABLE parent (id int4range NOT NULL, valid_at int4range NOT NULL);
  CREATE TABLE child (id int4range NOT NULL, valid_at int4range NOT NULL);
  INSERT INTO parent VALUES ('[1,2)', '[0,10)');
}
teardown { DROP TABLE child, parent; }

session s1
step exclusion {
  ALTER TABLE parent ADD CONSTRAINT parent_key
    EXCLUDE USING gist (id WITH =, valid_at WITH &&);
  ALTER TABLE child ADD CONSTRAINT child_fk
    FOREIGN KEY (id, PERIOD valid_at) REFERENCES parent (id, PERIOD valid_at);
}
step temporal_pk {
  ALTER TABLE parent ADD CONSTRAINT parent_key
    PRIMARY KEY (id, valid_at WITHOUT OVERLAPS);
  ALTER TABLE child ADD CONSTRAINT child_fk
    FOREIGN KEY (id, PERIOD valid_at) REFERENCES parent (id, PERIOD valid_at);
}
step s1begin { BEGIN ISOLATION LEVEL READ COMMITTED; }
step s1insert { INSERT INTO child VALUES ('[1,2)', '[0,10)'); }
step s1commit { COMMIT; }
step result {
  SELECT * FROM parent;
  SELECT c.*, coalesce(c.valid_at <@
    (SELECT range_agg(p.valid_at) FROM parent p WHERE p.id = c.id), false)
    AS covered FROM child c;
}
step validate {
  ALTER TABLE child DROP CONSTRAINT child_fk;
  ALTER TABLE child ADD CONSTRAINT child_fk
    FOREIGN KEY (id, PERIOD valid_at) REFERENCES parent (id, PERIOD valid_at);
}

session s2
step s2begin { BEGIN ISOLATION LEVEL READ COMMITTED; }
step s2shrink { UPDATE parent SET valid_at = '[0,5)' WHERE id = '[1,2)'; }
step s2commit { COMMIT; }


# this permutation shows a wrong result, as noticeable by the result and
# validate step outputs
permutation exclusion s1begin s2begin s1insert s2shrink s1commit s2commit result validate

# when a PK is also present everything works.
permutation temporal_pk s1begin s2begin s1insert s2shrink s1commit s2commit result validate