Index Usage in View with Aggregates

I have never had this particular problem in PostgreSQL, it seems to
"just know" when queries can be "flattened" and indexes used.  I know
that takes tons of work.  Thank you for that.

Here's the Oracle question.

http://stackoverflow.com/questions/1439500/oracle-index-usage-in-view-with-aggregates

I suspect I have made some subtle mistake in changing that SQL into a
view that is breaking Oracle's ability to know that an index can be
used.  Any and all advice is appreciated.

- Ian