Re: Error message inconsistency

On Sun, Mar 24, 2019 at 11:53 PM Simon Riggs <simon@2ndquadrant.com> wrote:
>
> On Sun, 24 Mar 2019 at 13:02, Amit Kapila <amit.kapila16@gmail.com> wrote:
>>
>> I think we are inconsistent for a similar message at a few other
>> places as well.  See, below two messages:
>>
>> column \"%s\" contains null values
>> column \"%s\" of table \"%s\" contains null values
>>
>> If we decide to change this case, then why not change another place
>> which has a similar symptom?
>
>
> Yes, lets do that.
>
> I'm passing on feedback, so if it applies in other cases, I'm happy to change other common cases also for the benefit
ofusers. 
>
> Do you have a list of cases you'd like to see changed?
>

I think we can once scrutinize all the error messages with error codes
ERRCODE_NOT_NULL_VIOLATION and ERRCODE_CHECK_VIOLATION to see if
anything else need change.

>>
>> > > It causes breakage in multiple tests, which is easy to fix once/if we agree to change.
>> > >
>> >
>> > I totally agree with that change because I already get some negative feedback from users about this message too.
>> >
>>
>> What kind of negative feedback did you get from users?  If I see in
>> the log file, the message is displayed as :
>>
>> 2019-03-24 18:12:49.331 IST [6348] ERROR:  null value in column "id"
>> violates not-null constraint
>> 2019-03-24 18:12:49.331 IST [6348] DETAIL:  Failing row contains (null).
>> 2019-03-24 18:12:49.331 IST [6348] STATEMENT:  insert into nn values (NULL);
>>
>> So, it is not difficult to identify the relation.
>
>
> The user is not shown the failing statement, and if they are, it might have been generated for them.
>

I can imagine that in some cases where queries/statements are
generated for some application, they might be presented just with
errors that occurred while execution and now it will be difficult to
identify the relation for which that problem has occurred.

> Your example assumes the user has access to the log, that log_min_error_statement is set appropriately and that the
usercan locate their log entries to identify the table name. The log contains timed entries but the user may not be
awareof the time of the error accurately enough to locate the correct statement amongst many others. 
>
> If the statement is modified by triggers or rules, then you have no chance.
>
> e.g. add this to the above example:
>
> create or replace rule rr as on insert to nn2 do instead insert into nn values (new.*);
>
>
> and its clear that the LOG of the statement, even if it is visible, is misleading since the SQL refers to table nn,
butthe error is generated by the insert into table nn2. 
>

This example also indicates that it will be helpful for users to see
the relation name in the error message.

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com