Indexing
========

The indexing omits the table BY_SPO, indexing on all three arguments but
uses BY_SP instead.  It  was  thought  not   to  gain  that  much.  This
assumption was verified  on  real   data  (100,000  triple). Introducing
BY_SPO gave a slowdown of about 10%.  Appearently the relatively high cost
for indexing on the complicated object field outweights the benefits.

The patch is left for reference in BY_SPO.diff. Note that after applying
this patch the test cases no  longer   pass.  As  the failing cases were
irrelevant to the performance test I never   bothered fixing this due to
the failed performance test.
