From: Tom Lane <tgl@sss.pgh.pa.us>
To: "David G. Johnston" <david.g.johnston@gmail.com>
cc: Valerio Battaglia <vabatta@gmail.com>,
        "pgsql-novice@lists.postgresql.org"
 <pgsql-novice@lists.postgresql.org>
Subject: Re: How to get column,
 table or parameter name reporting when violating DOMAIN type constraint
In-reply-to: 
 <CAKFQuwa00CR2HPxmngsGqx0mGOc4j215gZ4j_v32OYO_gfpQYg@mail.gmail.com>
References: 
 <CACxJNSkpT8vC0jnsfObZDargLA1vCiP-VKF2ji9y58VaAOSpVA@mail.gmail.com>
 <CAKFQuwYJtF-5Uvqo6ahKkeEAxOKta_yVb3n3at5Y=mvSgC0FrA@mail.gmail.com>
 <2911010.1679844383@sss.pgh.pa.us>
 <CAKFQuwa00CR2HPxmngsGqx0mGOc4j215gZ4j_v32OYO_gfpQYg@mail.gmail.com>
Comments: In-reply-to "David G. Johnston" <david.g.johnston@gmail.com>
	message dated "Sun, 26 Mar 2023 08:36:58 -0700"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <2914597.1679846405.1@sss.pgh.pa.us>
Date: Sun, 26 Mar 2023 12:00:05 -0400
Message-ID: <2914598.1679846405@sss.pgh.pa.us>
Archived-At: 
 <https://www.postgresql.org/message-id/2914598.1679846405%40sss.pgh.pa.us>
Precedence: bulk

"David G. Johnston" <david.g.johnston@gmail.com> writes:
> On Sunday, March 26, 2023, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> More to the point, you have the wrong mental model: a domain constraint
>> violation might not be associated with a table column at all.

> I disagree that the mental model is wrong.

The OP is asking for action-at-a-distance.  There are probably cases
where the distance is short enough that we could associate the runtime
error with a particular insertion target column, but I don't think it
could possibly be made to work for every sort of insert/select query.
In any case, the possibility of a hypothetical future feature (which
nobody is actively working on AFAIK) doesn't seem like a very useful
answer here.

> There are existing threads that I may hunt later.  IIRC, you (Tom) even
> suggested a possible way forward on this last time it came up.

I recall proposing that we try to produce syntax-error-like error
cursors for runtime errors, but it's not apparent to me that that'd
be tremendously applicable to the OP's problem.  The output would
look something like

ERROR: value for domain my_domain violates check constraint "value_min"
LINE 1: SELECT my_function(100, -100);
                                ^

which might be helpful for a human, but probably not very much so
for a program.  (BTW, this illustrates another issue: I'm pretty
sure that in the given case, the error is thrown while evaluating
my_function's arguments, long before we get within hailing distance
of any INSERT at all.)

			regards, tom lane