[postgis-users] Strange behaviour of = operator

[Mark Cave-Ayland]

> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-users-
> bounces at postgis.refractions.net] On Behalf Of strk at refractions.net
> Sent: 07 February 2006 16:08
> To: 'PostGIS Users Discussion'
> Subject: Re: [postgis-users] Strange behaviour of = operator

(cut)

> I think that FUNCTION 1 of btree opclass wants a comparator,
> returning -1, 0, 1 for less then, equal, greater then.
> Please correct me if I'm wrong.
> 
> --strk;


Hi strk,

Yeah looking closer at the docs you are indeed correct. I guess you could
swap the "return 0" and "return 1" around, but while that would work for
equality, you'd need some other metric for less than/greater than. Would it
useful to test for area in these cases? e.g.


create or replace function btree_equals_opclass(geometry, geometry) 
returns integer as $$
  begin
  if equals($1,$2) then
    return 0;
  else
    if area($1) < area($2) then
	return -1;
    else
      return 1;
    end if;
  end if;
end;
$$
language plpgsql;



Kind regards,

Mark.

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