Undocumented `*` in PostgreSQL tsquery?

Question

I was playing with tsquery and found that I can use * alone, (not as in foo:*), and it is accepted, but I have no idea of the behavior of this operator or if it is safe to use it

Here is an example

SELECT *, ts_rank_cd(x, query) AS rank
FROM to_tsquery('cat & *') query,
    (VALUES 
      (to_tsvector('cat say meow')),
      (to_tsvector('dog say woof'))) as t(x)
WHERE query @@ t.x

Here is a dbfidle with it https://www.db-fiddle.com/f/4jyoMCicNSZpjMt4jFYoz5/9036

It returns

| query | x                        | rank |
| ----- | ------------------------ | ---- |
| 'cat' | 'cat':1 'meow':3 'say':2 | 0.1  |

If I try it alone like to_tsquery('*'), it returns 0 rows. Does anybody know the behavior of this operator, or if is documented anywhere?

The documentation pages I checked were these:

• https://www.postgresql.org/docs/current/datatype-textsearch.html
• https://www.postgresql.org/docs/current/textsearch.html

---

Update

I think it is recognized as a punctuation, because ? or . works in the same way, the pertinent question is what punctuation matches?

Answer 1

The * is ignored:

SELECT to_tsquery('cat & *');

 to_tsquery 
════════════
 'cat'
(1 row)

So it is safe to use, but pointless.

* is nothing special here: the same happens with all characters that are not letters. They are simply ignored in full-text search.