Re: patch: function xmltable

2016-09-16 1:44 GMT+02:00 Craig Ringer <craig(at)2ndquadrant(dot)com>:

> On 15 September 2016 at 19:31, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
> wrote:
>
> > b_expr enforces shift/reduce conflict :(
>
> No problem then. I just thought it'd be worth allowing more if it
> worked to do so.
>
> > I found other opened question - how we can translate empty tag to SQL
> value?
> > The Oracle should not to solve this question, but PostgreSQL does. Some
> > databases returns empty string.
>
> Oracle doesn't solve the problem? it ERRORs?
>

Oracle returns NULL. But there are not any difference between NULL and
empty string

Regards

Pavel

>
> > I prefer return a empty string - not null in this case.
>
> I agree, and that's consistent with how most XML is interpreted. XSLT
> for example considers <x></x> and <x/> to be pretty much the same
> thing.
>
> > The reason is simple
> > - Empty string is some information - and NULL is less information. When
> it
> > is necessary I can transform empty string to NULL - different direction
> is
> > not unique.
>
> Yep, I definitely agree. The only issue is if people want a DEFAULT to
> be applied for empty tags. But that's something they can do in a
> post-process pass easily enough, since XMLTABLE is callable as a
> subquery / WITH expression / etc.
>
>
> --
> Craig Ringer http://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Training & Services
>