On Mon, 2009-07-06 at 11:56 +0100, Simon Riggs wrote: > I think it will be useful to separate the concepts of a constraint from > the concept of an index. It seems possible to have a UNIQUE constraint > that doesn't help at all in locating rows, just in proving that the rows > are unique.
That would be interesting. Do you have a use case? Checking the constraint would surely be slower in a lot of cases. I could imagine different constraint-checking schemes that could be fast against a heap. For instance, if it's greater than the max or less than the min value, that would be cheap to check. That might be an interesting way to handle the constraint for a sequence-generated column, or timestamp column that is always ascending. However, the problem is I don't see a lot of room for a practical use case. In the above situations, you'd almost certainly want indexes anyway: what's the point of a sequence number unless you're going to do lookups? And if you have an ascending timestamp column, I would think that you might do range lookups occasionally (which will be even better because the heap will be clustered). 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