Re: Make foo=null a warning by default.

> On Tue, Aug 7, 2018 at 11:19 PM Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>
> On Mon, Jul 16, 2018 at 11:37:28AM -0400, Tom Lane wrote:
> > Heikki Linnakangas <hlinnaka(at)iki(dot)fi> writes:
> > > On 16/07/18 18:10, Tom Lane wrote:
> > >> TBH I'm not really excited about investing any work in this area at all.
> > >> Considering how seldom we hear any questions about transform_null_equals
> > >> anymore[1], I'm wondering if we couldn't just rip the "feature" out
> > >> entirely.
> >
> > > Yeah, I was wondering about that too. But Fabien brought up a completely
> > > new use-case for this: people learning SQL. For beginners who don't
> > > understand the behavior of NULLs yet, I can see a warning or error being
> > > useful training wheels. Perhaps a completely new "training_wheels=on"
> > > option, which could check may for many other beginner errors, too, would
> > > be better for that.
> >
> > Agreed --- but what we'd want that to do seems only vaguely related to
> > the existing behavior of transform_null_equals. As an example, we
> > intentionally made transform_null_equals *not* trigger on
> >
> > CASE x WHEN NULL THEN ...
> >
> > but a training-wheels warning for that would likely be reasonable.
> >
> > For that matter, many of the old threads about this are complaining
> > about nulls that aren't simple literals in the first place. I wonder
> > whether a training-wheels feature that whined *at runtime* about null
> > WHERE-qual or case-test results would be more useful than a parser
> > check.
>
> I will again say I would love to see this as part of a wholesale
> "novice" mode which warns of generally bad SQL practices. I don't see
> this one item alone as sufficiently useful.

Valid point. Maybe then at least we can outline what kind of bad SQL practices
could be included into this "novice mode" to make it sufficiently useful?
Otherwise this sounds like a boundless problem.