Sarven Capadisli wrote:
> SELECT DISTINCT ?g
> WHERE {
> GRAPH ?g {
> ?s ?p ?o .
> }
> }
Hi Sarven,
asking for a list of the graphs in an RDF dataset is IMHO a pretty reasonable
use case and thing to do.
Your query, however, I suspect scan through all your data. This would explain
timeouts and long running times.
One suggestion is: if you are sure each graph has some specific triples and/or
properties, you could make the ?s ?p ?o triple pattern more specific and reduce
the amount of bindings/data. This might not be possible.
Another way would be to see if this pattern can be spotted by the optimizer and
do it in a better way. We could use the GSPO index (which is sorted by G, then
S, then P, then O) and apply the "reduced" operation of the SPARQL algebra which
over a sorted stream is equivalent to "distinct". I think it should work.
If others think this is a good idea, I'll go ahead, create a JIRA issue and
try to do it.
Listing the graphs in an RDF dataset seems to me quite an important and common
use case, don't you agree?
My 2 cents,
Paolo
