On Mon, 2005-02-28 at 18:01 -0700, Andrew - Supernews wrote: > The CHECK is obviously being evaluated prior to the actual insertion > of > the record, whereas the logic of your function clearly expects to be > evaluated after the insertion. >
I finally came to that conclusion just a few minutes before I got this email. However, it was your email that made it quite clear why this was. > Allowing non-immutable functions in CHECK is probably an error, since > it > can lead to tables which can not be dumped+restored (consider in your > example what happens when the constraint becomes false as a result of > deleting a row - at that point, a dump and restore of the table will > fail, > since the constraint can not be defined after loading the data if it > is > violated by that data). > Using triggers is a more reliable way to do this sort of thing - at > least > then it is clear that you are checking the data only at the time of > modification, whereas CHECK constraints are declarative constraints > which > are expected to be true at all times. > This is a very good point. I've now implemented the check with a trigger, and it works very well. Thanks for the input and the logic. Casey ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
