Marko Tiikkaja <marko.tiikkaja@cs.helsinki.fi> writes:
> On 2010-05-30 06:55 +0300, Robert Haas wrote:
>> I've often wished for the ability to constrain a tale to hold just one
>> row, so I don't find that use case implausible at all.
> As I pointed out in
> http://archives.postgresql.org/pgsql-hackers/2010-05/msg01177.php , you
> can already do that.
Yes. This is NOT about constraining a table to hold only one row.
It's about requiring all its rows to hold the same value (in some
column(s)), without predetermining exactly which value that will be.
I think the use-case for that is really extremely narrow.
regards, tom lane