Re: [BUGS] issue about information_schema REFERENTIAL_CONSTRAINTS

I have moved the text about duplicate constraints to the top of the
information schema section because it affects several tables (applied
patch attached). I could not figure out how to get the actual error
concept to the front of the paragraph.

---------------------------------------------------------------------------

Fabien COELHO wrote:
>
> Hello Bruce,
>
> >>>> Is that the direction we want to go, or would it be better to factor
> >>>> the information out into a separate page about compatibility gotchas?
> >>>
> >>> It would probably be better to explain globally applicable issues in a
> >>> separate section.
> >>
> >> I agree that a general caveat is better, together with a one line
> >> reference in the documentation of each table with an issue.
> >
> > Oh, I just noticed this. Can you give me a list of information_schema
> > tables that have this issue? I am only aware of
> > referential_constraints.
>
> Possibly any relation which references constraints with a (catalog,
> schema, name) triplet expecting it to be unique should have this issue.
>
> >From a quick scan on the information_schema, I would say:
> - check_constraint_routine_usage
> - check_constraints
> - constraint_column_usage (*)
> - constraint_table_usage (*)
> - domain_constraints
> - referential_constraints
> - table_constraints (*)
>
> For the three starred relations, the issue is not too big because a
> constraint name is unique per table in pgsql, and the table name is also
> given in these relations.
>
> This issue makes the "information_schema" pretty useless for being really
> use for serious work as the data can be ambiguous, so I still claim that
> for me this is a real "bug" rather than just a "feature", which is the
> status reached once a bug is documented:-)
>
> When constraint names are generated by postgresql, ISTM that the software
> is free to choose them so they could be chosen non ambiguous per schema.
>
> When users choose colliding names, I agree that it would break existing
> schemas, but there could be an option to enforce uniqueness of the name
> per schema if desired.
>
> I know there are some underlying issues with that that were discussed
> previously.
>
> Anyway I would appreciate something that it appears in the "todo" list,
> even if it is never implemented:-)
>
> --
> Fabien.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +