Re: Make foo=null a warning by default.

hOn Mon, Jul 16, 2018 at 11:37:28AM -0400, Tom Lane wrote:
> Heikki Linnakangas <hlinnaka@iki.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.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +