Using this will throw a "Exception in thread "main"
org.apache.jena.query.QueryParseException: Line 1, column 2: Aggregate
expression not legal at this point". So you may be right to use a query
builder :-)
On Fri, Dec 18, 2020 at 1:29 PM Andy Seaborne <a...@apache.org> wrote:
>
>
> On 18/12/2020 18:04, Erich Bremer wrote:
> > How would one create an Expr in order to add an expression like this:
> >
> > SPARQLParser p = SPARQLParser.createParser(Syntax.syntaxSPARQL_11);
> > Query query = new Query();
> > p.parse(query, "select ?year where {?s :Year ?year; :Fruit ?fruit} group
> by
> > ?year order by ?year");
> > query.addResultVar("fruits","(count(?fruit))");
> >
> >
> > query. addResultVar doesn't have a (String,String) but a (String,Expr)
>
> Expr expr = ExprUtils.parse("?x + ?y");
>
> But parsing count isn't so simple - it's an aggregate function.
>
> Aggregator agg = AggregatorFactory.createCount(true);
> Expr exprAgg = query.allocAggregate(agg) ;
> query.addResultVar("hello", exprAgg);
>
> It may be better to use the query builder.
>
> Andy
>
> >
> > SelectHandler has a private function "parseExpr" which I pulled out a
> copy
> > and modified it to (Query, String) to allow passing of an external Query
> > rather than the SelectHandler class variable query and it worked, but, is
> > there an already built in function that does the same or is there an
> easier
> > way to achieve the same result? - Erich
> >
>
