From: Peter Eisentraut <peter@eisentraut.org>
To: Navrátil, Ondřej <onavratil@monetplus.cz>
To: pgsql-docs@lists.postgresql.org
Subject: Re: COALESCE documentation
Date: Wed, 3 Jul 2024 11:00:17 +0200
Message-ID: <62f888dc-1ee5-48cf-b76c-6a75dcfa8b10@eisentraut.org> (raw)
In-Reply-To: <CAEELDaqnn5GayihUUhnKLR1_fegb-_b2i+4_dP4U192uK7j9vw@mail.gmail.com>
References: <CAEELDaqnn5GayihUUhnKLR1_fegb-_b2i+4_dP4U192uK7j9vw@mail.gmail.com>
On 02.07.24 12:45, Navrátil, Ondřej wrote:
> Hello,
>
> as per documentation
> <https://www.postgresql.org/docs/current/functions-conditional.html#FUNCTIONS-COALESCE-NVL-IFNULL;
> > The |COALESCE| function returns the first of its arguments that is
> not null. Null is returned only if all arguments are null.
>
> This is not exactly true. In fact:
> The |COALESCE| function returns the first of its arguments that *is
> distinct* *from *null. Null is returned only if all arguments *are not
> distinct from* null.
>
> See my stack overflow question here
> <https://stackoverflow.com/questions/78691097/postgres-null-on-composite-types;.
>
> Long story short
>
> |select coalesce((null, null), (10, 20)) as magic; |
>
> returns
>
> |magic ------- (,) (1 row)|
>
> However, this is true:
>
> |select (null, null) is null;|
I think this is actually a bug in the implementation, not in the
documentation. That is, the implementation should behave like the
documentation suggests.
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To: pgsql-docs@postgresql.org
Cc: peter@eisentraut.org, onavratil@monetplus.cz, pgsql-docs@lists.postgresql.org
Subject: Re: COALESCE documentation
In-Reply-To: <62f888dc-1ee5-48cf-b76c-6a75dcfa8b10@eisentraut.org>
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