=?UTF-8?Q?Torsten_F=C3=B6rtsch?= <tfoertsch123@xxxxxxxxx> writes: > My question is can I somehow express something like > EXCLUDE (c1 WITH =, c2 with NOT =) > It seems that's not possible at the moment. But is there any obstacle in > principle or is it just not implemented? Well, it'd likely be a bad idea. Indexes are meant to help you quickly find a small part of a table that satisfies a condition. Finding the probably-much-larger part of the table that doesn't satisfy the condition is something they are bad at. This is why "=" is an indexable operator while "<>" is not. It's not impossible in principle for "<>" to be an index operator, but the set of cases where indexing on such a condition would beat a seqscan is likely to be uselessly small. By the same token, EXCLUDE constraints using such a condition would be unpleasantly inefficient. regards, tom lane
