To: Fabien COELHO <coelho@cri.ensmp.fr>
cc: Bruce Momjian <bruce@momjian.us>, Peter Eisentraut <peter_e@gmx.net>,
	Alvaro Herrera <alvherre@commandprompt.com>, pgsql-docs@postgresql.org
Subject: Re: [BUGS] issue about information_schema REFERENTIAL_CONSTRAINTS 
In-reply-to: <alpine.DEB.2.00.1102200825550.2423@localhost6.localdomain6> 
References: <201102200011.p1K0B1l06164@momjian.us>
	<alpine.DEB.2.00.1102200825550.2423@localhost6.localdomain6>
Comments: In-reply-to Fabien COELHO <coelho@cri.ensmp.fr>
	message dated "Sun, 20 Feb 2011 08:48:21 +0100"
Date: Sun, 20 Feb 2011 10:35:27 -0500
Message-ID: <28932.1298216127@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Fabien COELHO <coelho@cri.ensmp.fr> writes:
> 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.

We do that already.  See ChooseConstraintName and ChooseRelationName.

> 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.

What would be the point of that?  IIRC, your complaint about this was in
connection with wanting to write some information-schema-using code that
could be used by anybody.  Such code could hardly assume that the option
was set.

Basically, the only way to satisfy your request is to take freedom away
from our users, and we're unlikely to do that.

			regards, tom lane