Theo Kramer <theo@xxxxxxxxxxx> writes: > If so, I would appreciate any pointers on where to start on this - > already fumbling my way through Interfacing Extensions To Indexes in the > manual... Search the PG list archives for discussions of reverse-sort opclasses. It's really pretty trivial, once you've created a negated btree comparison function for the datatype. This is the sort of thing that we are almost but not quite ready to put into the standard distribution. The issues that are bugging me have to do with whether NULLs sort low or high --- right now, if you make a reverse-sort opclass, it will effectively sort NULLs low instead of high, and that has some unpleasant consequences because the rest of the system isn't prepared for variance on the point (in particular I'm afraid this could break mergejoins). I'd like to see us make "NULLs low" vs "NULLs high" be a defined property of opclasses, and deal with the fallout from that, and then we could put reverse-sort opclasses for all the standard datatypes into the regular distribution. regards, tom lane
