Re: Multi ordered select and indexing

"Antal Attila" <antal(dot)attila(at)ritek(dot)hu> writes:
> CREATE OPERATOR CLASS int4_reverse_order_ops
> FOR TYPE int4 USING btree AS
> OPERATOR 1 /< ,
> OPERATOR 2 /<= ,
> OPERATOR 3 /= ,
> OPERATOR 4 />= ,
> OPERATOR 5 /> ,
> FUNCTION 1 int4_reverse_order_cmp(int4, int4);

This is the wrong way to go about it. A useful descending-order opclass
simply rearranges the logical relationships of the standard comparison
operators. You do need a new comparison function, but nothing else:

CREATE OPERATOR CLASS int4_reverse_order_ops
FOR TYPE int4 USING btree AS
OPERATOR 1 > ,
OPERATOR 2 >= ,
OPERATOR 3 = ,
OPERATOR 4 <= ,
OPERATOR 5 < ,
FUNCTION 1 int4_reverse_order_cmp(int4, int4);

Now you can just use ASC/DESC in your ORDER BY ...

regards, tom lane