pg_sorttemp hits 2GB during index construction

I am trying to make an index on three columns (text, int2, date)
on a table with 193 million records.   I believe I am finding that
the pg_sorttemp files reach 2GB before the index finishes. 
The backend finishes the index but it's clearly missing tuples.

Does this make sense to you folks?

--Martin

P.S. My text field only contains a single char and I realize that
I was foolish not use a char(1) instead of varchar . . .