Re: Unexpected zero results

Viliam Ďurina schrieb am 23.03.2022 um 17:56:
> Hello all,
>
> I'm experimenting with JSON-path functions, and stumbled upon this query:
>
>    SELECT jsonb_path_query('[1,2,3]', '$[*]?(@ == 4)')
>
> It returns 0 rows. I expected it to return one row with `null` value.
> Isn't it the case that `SELECT <some expression>` should always
> return 1 row?

jsonb_path_query is a set returning function, so it's actually more like this:

     SELECT *
     FROM jsonb_path_query('[1,2,3]', '$[*]?(@ == 4)')

Then it's obvious why no row is returned.

That's one of the reasons I never use set-returning functions in the SELECT list.