Re: jsonb_set() strictness considered harmful to data

[Steven Pousty]

On Sun, Oct 20, 2019 at 4:31 PM raf  wrote:

> Steven Pousty wrote:
>
> > I would think though that raising an exception is better than a
> > default behavior which deletes data.
>
> I can't help but feel the need to make the point that
> the function is not deleting anything. It is just
> returning null. The deletion of data is being performed
> by an update statement that uses the function's return
> value to set a column value.
>
> I don't agree that raising an exception in the function
> is a good idea (perhaps unless it's valid to assume
> that this function will only ever be used in such a
> context). Making the column not null (as already
> suggested) and having the update statement itself raise
> the exception seems more appropriate if an exception is
> desirable. But that presumes an accurate understanding
> of the behaviour of jsonb_set.
>
> Really, I think the best fix would be in the
> documentation so that everyone who finds the function
> in the documentation understands its behaviour
> immediately.
>
>
>
Hey Raf

In a perfect world I would agree with you. But often users do not read ALL
the documentation before they use the function in their code OR they are
not sure that the condition applies to them (until it does).  Turning a
JSON null into a SQL null  and thereby "deleting" the data is not the path
of least surprises.

So while we could say reading the documentation is the proper path it is
not the most helpful path. I am not arguing against doc'ing the behavior no
matter what we decide on. What I am saying is an exception is better than
the current situation if we can't agree to any other solution. An exception
is better than just doc but probably not the best solution. (and it seems
like most other people have said as well but the lag on a mailing list is
getting us overlapping).

I see people saying Null pointer exceptions are not helpful. I mostly
agree, they are not the most helpful kind of exception BUT they are better
than some alternatives. So I think it would be better to say NPEs are not
as helpful as they possibly could be.

Re: jsonb_set() strictness considered harmful to data

[Steven Pousty]

I would think though that raising an exception is better than a default
behavior which deletes data.
As an app dev I am quite used to all sorts of "APIs" throwing exceptions
and have learned to deal with them.

This is my way of saying that raising an exception is an improvement over
the current situation. May not be the "best" solution but definitely an
improvement.
Thanks
Steve

On Sun, Oct 20, 2019 at 12:48 PM Andrew Dunstan <
andrew.duns...@2ndquadrant.com> wrote:

>
> On 10/20/19 1:14 PM, David G. Johnston wrote:
> > On Sun, Oct 20, 2019 at 5:31 AM Andrew Dunstan
> >  > > wrote:
> >
> > And yet another is to
> > raise an exception, which is easy to write but really punts the issue
> > back to the application programmer who will have to decide how to
> > ensure
> > they never pass in a NULL parameter.
> >
> >
> > That's kinda the point - if they never pass NULL they won't encounter
> > any problems but as soon as the data and their application don't see
> > eye-to-eye the application developer has to decide what they want to
> > do about it.  We are in no position to decide for them and making it
> > obvious they have a decision to make and implement here doesn't seem
> > like a improper position to take.
>
>
> The app dev can avoid this problem today by making sure they don't pass
> a NULL as the value. Or they can use a wrapper function which does that
> for them. So frankly this doesn't seem like much of an advance. And, as
> has been noted, it's not consistent with what either MySQL or MSSQL do.
> In general I'm not that keen on raising an exception for cases like this.
>
>
> cheers
>
>
> andrew
>
>
> --
> Andrew Dunstanhttps://www.2ndQuadrant.com
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>
>
>
>