Re: Multi ordered select and indexing

"Antal Attila" <antal.attila@ritek.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