Re: Does anybody use ORDER BY x USING y?

Tom Lane wrote:

>Hannu Krosing <hannu@skype.net> writes:
>  
>
>>I think that placement of NULL's should be a property of ORDER BY and
>>separated from opclass.
>>    
>>
>
>That would be an extremely bad idea, because it would immediately remove
>index scans as one way to meet an ORDER BY.  I'm thinking in terms of
>NULL high/low as becoming a property of btree opclasses so that indexes
>know what to do with nulls, and so that the planner can tell whether a
>given index meets the required sort ordering or not.
>
>Alternatively we could define an index's ordering as being specified by
>both an opclass and a NULL direction, but that doesn't seem better to
>me; especially since the null-direction concept doesn't seem meaningful
>for non-btree indexes at all, but a structure like that would require us
>to associate a null-direction with all indexes.
>
>
>  
>

Not sure I understand ... in fact I am sure I don't :-)

Are you envisioning that the null direction will be able to be selected 
at the time of the select statement?

cheers

andrew