From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andrew Gierth <andrew@tao11.riddles.org.uk>
Cc: André Hänsel <andre@webkr.de>
Cc: pgsql-bugs@postgresql.org
Subject: Re: Two constraints with the same name not always allowed
Date: Sun, 02 Sep 2018 13:00:45 -0400
Message-ID: <10110.1535907645@sss.pgh.pa.us> (raw)
In-Reply-To: <87in3ovy0r.fsf@news-spur.riddles.org.uk>
References: <0c1001d4428f$0942b430$1bc81c90$@webkr.de>
<87in3ovy0r.fsf@news-spur.riddles.org.uk>
Andrew Gierth <andrew@tao11.riddles.org.uk> writes:
> "André" == André Hänsel <andre@webkr.de> writes:
> André> Case 2:
> André> CREATE TABLE t(c integer);
> André> ALTER TABLE t ADD CONSTRAINT foo CHECK(c > 1);
> André> ALTER TABLE t ADD CONSTRAINT foo UNIQUE(c);
> André> -> Creates two constraints, both called "foo".
> I'd call _that_ a bug, myself - having two constraints on a table with
> the same name potentially messes up a lot of automated maintenance
> operations.
Agreed. We must have missed a check for constraint-exists someplace.
This also points up the lack of a suitable unique index on pg_constraint.
It's sort of difficult to figure out what that should look like given that
pg_constraint contains two quasi-independent collections of constraints,
but maybe UNIQUE(conrelid,contypid,conname) would serve given the
reasonable assumption that exactly one of conrelid and contypid is zero.
Potentially we could drop pg_constraint_conrelid_index and
pg_constraint_contypid_index, replacing scans on those with
scans on this new unique index.
regards, tom lane
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To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, andrew@tao11.riddles.org.uk, andre@webkr.de
Subject: Re: Two constraints with the same name not always allowed
In-Reply-To: <10110.1535907645@sss.pgh.pa.us>
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