I have a large table in which a small percentage of the records have identical values in a particular key field. What is the most efficient way to count the number of records having a particular value in the key field. If I'm only interested in a particular key value, searching by filtering seems like a pretty sexy way to do it, but do the realities of filter implementation indicate against it for large files?

1) ordering off, count for keyname = value all
(key is in active .cdx file)
2) order by key, count for keyname = value all
3) order by key, seek keyname = value, count for keyname rest
4) ordering off, set filter to keyname = value then count all
5) order by key, set filter to keyname = value then count all
6) order by key, seek keyname, set filter to keyname = value
then count all
7) order by key, seek keyname, iterate a do loop to count
while skipping
8) something else I haven't thought of...
9) Rushmore is so efficient that for a the trivial key expression
given above, all of these are about the same.