Re: enhanced error fields

Hello

From my perspective - the core of this patch has two parts

a) necessary infrastructure
b) enhancing current ereport calls

@a point is important for me and plpgsql coders, because it allows
using these fields in custom PL/pgSQL exception - and errors
processing in this language can be more structurable and comfortable.
But now we are too late - and this part can be commited probably in
9.4 - although I have this patch prepared.

@b is important for application users - but there was agreement so we
will coverage exceptions step by step - so in this context we can drop
support for domains now.

2013/1/26 Tom Lane <tgl@sss.pgh.pa.us>:
> Peter Geoghegan <peter@2ndquadrant.com> writes:
>> [ eelog6.patch ]
>> So, with the question of what fields to include and whether constraint
>> name needs to be unambiguously resolvable addressed (I think), it
>> appears that I've brought this one as far as I can. I'd still like to
>> get input from a Perl hacker, but I think a committer needs to pick
>> this up now.
>
> I started to look this patch over.  I think we can get to something
> committable from here, but I'm having a problem with the concept that
> we're going to "guarantee" anything about which additional fields might
> be available for any given SQLSTATE.  This is already quite broken for
> the ERRCODE_NOT_NULL_VIOLATION case, and it's not hard to envision that
> there will be other inconsistencies in future, even without the issue
> that third-party code might use these SQLSTATEs without having gotten
> the memo about additional fields.

>
> If we were doing this from scratch we could perhaps fix that by using,
> eg, two different SQLSTATEs for the column-not-null and
> something-else-not-null cases.  But it's probably too late to change the
> SQLSTATEs for existing error cases; applications might be depending on
> those.  Anyway our choice of SQLSTATE is often constrained by the
> standard.
>
> I'm inclined to remove the "requirements" business altogether and just
> document that these fields may be supplied, or words to that effect.
> In practice, an application is going to know whether the particular
> error case it's concerned about has the auxiliary fields, I should think.
>
>> We also go to extra lengths to get a table_name for certain
>> domain-related ereport sites.
>
> A lot of that looks pretty broken to me, eg the changes in
> ExecEvalCoerceToDomain are just hokum.  (Even if the expression is
> executing in a statement that has a result table, there's no very good
> reason to think that the error has anything to do with the result
> table.)  It's possible we could restructure things so that coercions
> performed as part of an assignment to a specific table column are
> processed differently from other coercions, and have knowledge available
> about what the target table/column is.  But it would be a pretty
> invasive change for limited benefit.

>
> BTW, one thing that struck me in a quick look-through is that the
> ERRCODE_FOREIGN_KEY_VIOLATION patches seem to inconsistently send
> either the PK or FK rel as the "errtable".  Is this really per spec?
> I'd have sort of expected that the reported table ought to be the one
> that the constraint belongs to, namely the FK table.
>

Today I'll to spec

Pavel

>                         regards, tom lane