Hi Andy In any case, why is there the need for the assign node? Why not simply:
> (project (?p ?asvar) > (group (?p) ((?asvar (count ?b))) -- diogo patrão On Sun, Mar 24, 2013 at 2:54 PM, Andy Seaborne <[email protected]> wrote: > On 22/03/13 17:43, Damian Steer wrote: > >> >> On 22 Mar 2013, at 17:01, Diogo FC Patrao <[email protected]> wrote: >> >> I'm rendering back the query, implementing the OpAsQuery missing methods. >>> However I got another doubt, check the query below: >>> >>> select ?p count( ?b ) { ?p a <http://marafo.com#Paciente>. ?a < >>> http://marafo.com#tem> ?b. LET ( ?marafo := ?b+1 ) } group by ?p >>> >>> >>> The generated algebra is: >>> >>> (project (?p ?.1) >>> >>> (assign ((?.1 ?.0)) >>> >>> (group (?p) ((?.0 (count ?b))) >>> >>> I didn't get why is there this "(assign (?.1 ?.0) ) " thing... can >>> someone >>> enlighten me? >>> >> >> AFAIK it's simply an artifact of way the compiler works. >> >> OpAsQuery handles this by remembering the aggregation as it goes (in >> varExpression) and undoes the split later: >> >> <https://github.com/apache/**jena/blob/trunk/jena-arq/src/** >> main/java/com/hp/hpl/jena/**sparql/algebra/OpAsQuery.java#**L523<https://github.com/apache/jena/blob/trunk/jena-arq/src/main/java/com/hp/hpl/jena/sparql/algebra/OpAsQuery.java#L523> >> > >> >> <https://github.com/apache/**jena/blob/trunk/jena-arq/src/** >> main/java/com/hp/hpl/jena/**sparql/algebra/OpAsQuery.java#**L56<https://github.com/apache/jena/blob/trunk/jena-arq/src/main/java/com/hp/hpl/jena/sparql/algebra/OpAsQuery.java#L56> >> > >> >> Damian >> >> > Here, it's not SPARQL 1.1 because there is no AS on the count(?b) > otherwise the (assign) would be (assign ((?AS_VAR ?.0)). The ?.1 is a > generated variable for the lack of AS with count(). > > Andy > >
