gist index on cube column

[ABHANG RANE <arane@xxxxxxxxxxx>]

Hi,
I had some doubts about the gist index on cube column. So if I have a 
column of type cube and create a gist index on it, would the index be 
on individual elements in the cube or the cube as a whole. I mean will 
a gist index on cube column improve the performance of earthdistance 
function or cube_distance function.

Thanks
Abhang