Question about ranking & full text

Hi,

I wonder why the third query returns 0.

To me, it would return 0.1, because there is not baz in the text

Thanks !

(pg 9.4)

SELECT ts_rank_cd(apod.t, query,4) AS rank
FROM (SELECT to_tsvector('foo baz') as t) as apod, to_tsquery('foo & baz') query
WHERE query @@ apod.t;
rank        |
------------|
0.100000001 |

SELECT ts_rank_cd(apod.t, query,4) AS rank
FROM (SELECT to_tsvector('foo ') as t) as apod, to_tsquery('foo & ! baz') query
WHERE query @@ apod.t;

rank        |
------------|
0.100000001 |

SELECT ts_rank_cd(apod.t, query,4) AS rank
FROM (SELECT to_tsvector('foo ') as t) as apod, to_tsquery(' ! baz') query
WHERE query @@ apod.t;

rank        |
------------|
0.0         |