BUG #13768: JSONB concat

The following bug has been logged on the website:

Bug reference: 13768
Logged by: Roman
Email address: awasarax(at)yandex(dot)ru
PostgreSQL version: 9.5beta1
Operating system: Windows (7, Server 2008 r2)
Description:

if "d" is null then return = null
else
return <> null

CREATE OR REPLACE FUNCTION userfunc(jsonb)
RETURNS jsonb AS
$BODY$
DECLARE
r jsonb = null;
d jsonb = null;
BEGIN
SELECT to_json(users.*) INTO r FROM users WHERE ///////;
RETURN r||d; -- return null
END;
$BODY$
LANGUAGE plpgsql VOLATILE;

awasarax(at)yandex(dot)ru writes:
> if "d" is null then return = null
> else
> return <> null

> CREATE OR REPLACE FUNCTION userfunc(jsonb)
> RETURNS jsonb AS
> $BODY$
> DECLARE
> r jsonb = null;
> d jsonb = null;
> BEGIN
> SELECT to_json(users.*) INTO r FROM users WHERE ///////;
> RETURN r||d; -- return null
> END;
> $BODY$
> LANGUAGE plpgsql VOLATILE;

I see nothing particularly wrong here. There is long-established
precedent, eg, 'foo'::text || NULL is null too. It makes sense
if you consider that NULL means "unknown".

regards, tom lane