"Kim Yunhan" <spbear(at)hanmail(dot)net> writes:
> then, how to make operator class?
See the Programmer's Guide, particularly
http://www.postgresql.org/devel-corner/docs/postgres/xindex.htm
If this is a followup to your previous question about making a
reverse-order index, you'll need to start by making a support function
that delivers the reverse (negative) of what the existing btree
comparison function for the datatype does (see btint4cmp and friends).
The remaining operators to comprise the opclass are the same ones that
exist already, you just need to swap their positions (use '<' for '>'
etc). Good luck!
regards, tom lane