| From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | Darryl Dixon <darryl(dot)dixon(at)gmail(dot)com> |
| Cc: | "pgsql-bugs(at)lists(dot)postgresql(dot)org" <pgsql-bugs(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: BUG #18451: NULL fails to coerce to string when performing string comparison |
| Date: | 2024-04-30 22:09:06 |
| Message-ID: | CAKFQuwZvPW+EH1cDCjti8EC_ke5-84Z6HBPjxfos4q4QUxuv-A@mail.gmail.com |
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| Lists: | pgsql-bugs |
On Tuesday, April 30, 2024, Darryl Dixon <darryl(dot)dixon(at)gmail(dot)com> wrote:
> Hi,
>
> There are a couple of notes regarding this:
> 1) There is an explicit CAST of NULL->text that silently fails (see
> original example)
>
It doesn’t fail. Casting null still results in null.
(Null::integer)::text is valid, you end up with a null integer converted
to a null of type text.
2) This behaviour, if expected, is not well documented/contradicted by
> existing documentation. See the note here:
> https://www.postgresql.org/docs/current/functions-string.html
>
Fair, we don’t explicitly document that ‘…’ || NULL yields NULL. It’s more
of “unless otherwise noted doing stuff with null results in unknown/null
outcomes”.
David J.
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