Long story short - I had two problems, but the primary is that Jena requires parenthesis and named var:
SELECT (COUNT(?resource) AS ?count) FROM <http://id.nlm.nih.gov/mesh> WHERE { ?resource a meshv:Descriptor . ?resource rdfs:label ?label . ?label bif:contains "Pyrin" . } The second problem was that ORDER BY screws up the results, because it prevented an automated grouping. On Sat, Mar 23, 2019 at 10:28 PM Dan Davis <dansm...@gmail.com> wrote: > I've now designed a unit test for the code above, and it works mostly as > intended. I still don't see how to get Count queries work as a > transformation. The documentation is clear that this should be supported, > as is the EBNF of the Sparql 1.1 specification. > > The next step was to make sure that I was telling qparse to treat my query > as sparql11: > > ~/tools/apache-jena/bin/qparse --query countquery --syntax=sparql11 > --print=op > > Finding the values of Syntax were not that easy, because the --help > doesn't provide the valid values of the syntax. Jshell did crack it > eventually: Syntax.querySyntaxNames.keys() > > Sigh - I'd rather be programming Python, but that's OK. > > On Fri, Mar 22, 2019 at 5:55 PM Dan Davis <dansm...@gmail.com> wrote: > >> >> Hi guys, I'm writing my first Transform, and I'm having trouble with a >> count query. >> arq.qparse doesn't parse and print my count query, so I cannot get much >> feedback whether I'm doing the right thing or not. >> >> A limit query seems simple enough, however: >> >> >> package gov.nih.nlm.lode.service; >> >> import com.hp.hpl.jena.sparql.algebra.Op; >> import com.hp.hpl.jena.sparql.algebra.TransformBase; >> import com.hp.hpl.jena.sparql.algebra.op.OpProject; >> import com.hp.hpl.jena.sparql.algebra.op.OpSlice; >> >> public class LimitTransform extends TransformBase { >> private long offset; >> private long limit; >> >> public LimitTransform(long limit, long offset) { >> this.limit = limit; >> this.offset = offset; >> } >> public LimitTransform(long limit) { >> this(limit, 0); >> } >> >> @Override >> public Op transform(OpProject opProject, Op subOp) { >> return new OpSlice(opProject, offset, limit); >> } >> } >> >> >> >> >>
