Re: enhanced error fields

> -----Original Message-----
> From: pgsql-hackers-owner@postgresql.org [mailto:pgsql-hackers-
> owner@postgresql.org] On Behalf Of Peter Geoghegan
> Sent: Monday, December 10, 2012 3:29 PM
> To: Pavel Stehule
> Cc: PostgreSQL Hackers; Alvaro Herrera; Tom Lane
> Subject: Re: [HACKERS] enhanced error fields
> 
> Now, there are one or two places where these fields are not actually
> available even though they're formally required according to a literal
reading
> of the above. This is only because there is clearly no such field sensibly
> available, even in principle - to my mind this cannot be a problem,
because
> the application developer cannot have any reasonable expectation of a
field
> being set. I'm really talking about two cases in particular:
> 
> * For ERRCODE_NOT_NULL_VIOLATION, we don't actually provide
> schema_name and table_name in the event of domains. This was previously
> identified as an issue. If it is judged better to not have any
requirements
> there at all, so be it.
> 
> * For the validateDomainConstraint() ERRCODE_CHECK_VIOLATION ereport
> call, we may not provide a constraint name iff a Constraint.connname is
> NULL. Since there isn't a constraint name to give even in principle, and
this is
> an isolated case, this seems reasonable.
> 

Just skimming this topic but if these enhanced error fields are going to be
used by software, and we have 99% adherence to a standard, then my first
reaction is why not just supply "" (or "" as
appropriate) instead of suppressing the field altogether in these (and
possibly other, future) cases and make adherence for these fields 100%?

From an "ease-of-use" aspect for the API if I can simply always query each
of those fields and know I will be receiving a string it does at least seem
theoretically easier to interface with.  If I am expecting special string
values (enclosed in symbols making them invalid identifiers) I can then
handle those as desired without either receiving an error or a NULL when I
go to poll the missing field if those couple of instances.

I may be paranoid or mistaken regarding how this work but figured I'd at
least throw it out for consideration.

David J.