On Wed, Mar 31, 2010 at 1:07 PM, Kevin Grittner <kevin.gritt...@wicourts.gov> wrote: > Robert Haas <robertmh...@gmail.com> wrote: > >> This says: >> >> Exclusion constraints ensure that that if any two rows are >> compared on the specified column(s) or expression(s) using the >> specified operator(s), not all of these comparisons will return >> <literal>TRUE</>. >> >> I think that's backwards - the last clause should say "none of >> those comparisons will return <literal>TRUE</>". >> >> Unless I'm confused. > > "not all" seems correct. For example, you could be checking the > room number for equality and a range of time for overlap -- both > must be TRUE to have a problem; otherwise you could only schedule > one thing in the room for all time and one thing at a given time > across all rooms.
Oh, I see. I thought it was referring to all pairs of rows, but I see now it's referring to pairs of columns, so it's correct. ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
