Re: How to get column, table or parameter name reporting when violating DOMAIN type constraint
| От | Valerio Battaglia |
|---|---|
| Тема | Re: How to get column, table or parameter name reporting when violating DOMAIN type constraint |
| Дата | |
| Msg-id | CACxJNS=sXe14q3o1_VXpU+fkuKcc5r09xqVLva68kY30hvf9qw@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: How to get column, table or parameter name reporting when violating DOMAIN type constraint (Tom Lane <tgl@sss.pgh.pa.us>) |
| Список | pgsql-novice |
Thanks for the answer and explanation. My reasoning behind the use of domains, particularly in function calls, is to have a useful approach for validating input before it enters a function. By doing so, it eliminates the need to manually verify input for public / exposed functions, and would effectively make domains provide an efficient way to encapsulate and enforce business rules.
Considering the aforementioned example, having a message reporting with the position name would make the consumer life much easier, program or human alike
SELECT my_function(100, -100);
-- ERROR: value "second_parameter" for domain my_domain violates check constraint "value_min"
SELECT (-1)::my_domain;-- ERROR: value "unnamed" for domain my_domain violates check constraint "value_min"
Valerio
On Sun, 26 Mar 2023 at 18:00, Tom Lane <tgl@sss.pgh.pa.us> wrote:
"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
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