Hi: On Tue, Jul 5, 2011 at 11:26 AM, Jeff Davis <pg...@j-davis.com> wrote: > In the 9.0 version of exclusion constraints, we added an extra check to > ensure that, when searching for a conflict, a tuple at least found > itself as a conflict. This extra check is not present in 9.1+. > > It was designed to help diagnose certain types of problems, and is fine > for most use cases. A value is equal to itself (and therefore conflicts > with itself), and a value overlaps with itself (and therefore conflicts > with itself), which were the primary use cases. We removed the extra > check in 9.1 because there are other operators for which that might not > be true, like <>, but the use case is a little more obscure. > > However, values don't always overlap with themselves -- for instance the > empty period (which was an oversight by me). So, Abel Abraham Camarillo > Ojeda ran into a rather cryptic error message when he tried to do that: > > ERROR: failed to re-find tuple within index "t_period_excl" > HINT: This may be because of a non-immutable index expression. > > I don't think we need to necessarily remove the extra check in 9.0, > because the workaround is simple: add a WHERE clause to the constraint > eliminating empty periods. Perhaps we could improve the error message > and hint, and add a note in the documentation.
That's what I'm doing now: using a where clause to workaround... it's easy, but I was still amazed about what that error message meant... Thanks. > Thoughts? > > Regards, > Jeff Davis > > > > -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
