Hi!
Obviously the
second query as written at the moment involves a
sub-query, which inevitably must make it a bit slower -- but given the
solution set of the sub-query only has two rows, and an exact date for a
given property ought to be a fairly quick key to look up, why is the
second query taking 100 times longer than the first ?
Yes, in theory it should be fast, so I suspect some kind of bug.
It looks like it is indeed a problem with query optimizer, and if you add:
hint:Query hint:optimizer "None" .
to the query, it becomes much better. In general, the optimizer for
Blazegraph is not perfect, so if some (especially complex) query behaves
weirdly, it may always be a good idea to try "no optimizer" hint and see
if it makes the matter better. Sometimes it does.
--
Stas Malyshev
smalyshev(a)wikimedia.org