Re: set constraints docs page

Kevin Brown wrote:
> Bruce Momjian wrote:
> > Kevin Brown wrote:
> > > The two approaches aren't necessarily mutually exclusive (though SQL99
> > > compliance on constraint names would obviously make it unnecessary to
> > > specify a tablename along with a constraint name), so I see little
> > > problem here.  But the current arrangement is obviously untenable,
> > > because it allows you to create a situation (multiple constraints by
> > > the same name) that you can't reasonably extricate yourself from.
> > 
> > Well, it seems if we want to continue to allow the same constraint name
> > to be used by different tables in the same schema, we have to print the
> > tablename in the error message.  Would someone actually be looking for a
> > standards-compliant error string?  We have already extended the standard
> > --- either we revert that, or we have to go the entire way and print the
> > table name.
> 
> If PG were configurable in terms of how it manages constraint names,
> then it would depend on how the DBA had the database configured.  With it
> configured to disallow name collisions, it would obviously be unnecessary
> to report the table name, though I still think it would be useful (if
> only because it gives a little extra context to work with).  But if it's
> configured to allow name collisions, then it doesn't make sense not to
> print the table name in an error message, because that's the only way to
> guarantee that the DBA can identify which constraint is being referred to.
> 
> 
> The problem as things stand now is that even if we printed the table name
> involved, the DBA is placed in a difficult position if the constraint in
> question isn't uniquely named -- which is the only case where printing
> the table name would really matter.  That's because he can't actually
> refer to the constraint in any unique way short of playing with the
> system tables; he'd have to rename the constraint first before being
> able to really do something with it (is this even possible for him to
> do without manipulating system tables?  Is there an ALTER CONSTRAINT?).

Added to TODO:
* Print table names with constraint names in error messages, or make  constraint names unique within a schema

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