On 12-03-08 02:47 PM, Paolo Castagna wrote:
Rob Vesse wrote:
Yes one possibility that me and Andy raised in that discussion was the
use of the following:
SELECT DISTINCT ?g WHERE { GRAPH ?g { } }
Since GRAPH ?g is defined as an iteration over all graphs in the dataset
(which may of course be modified by the presence of FROM and FROM NAMED)
and the empty graph pattern returns a single empty solution (i.e. always
matches) then on paper at least this query should do the same job and be
much more performant. Whether this query works may vary depending on
how accurately an engine actually implements the SPARQL spec because the
whole dataset/GRAPH interaction is one of the areas prone to ambiguities
in the spec and differences of opinion between implementers
Indeed, the optimization might already be there... Sarven, could you try to see
if SELECT DISTINCT ?g { GRAPH ?g { } } gives you what you want, faster?
First of all, that worked! It took about 10-15 minutes the first time I
tried it. I just ran it again.. and 30 minutes in, still waiting for a
response. Odd.
-Sarven
