[GitHub] [jena] afs commented on issue #1374: a convenient way to execute a query against graph in a dedicated context.

[GitBox <gi...@apache.org>]

afs commented on issue #1374:
URL: https://github.com/apache/jena/issues/1374#issuecomment-1153122216

   Hi @sszuev ,
   
   A copy of the context will share the original registries - the way to modify that is to modify the copy of the context. I'd put that code in the PropertyFunctionRegistry, not "teach" context about a specific setting - moie discussion for the PR - the copy operations look useful.
   
   The best control over a query setup is via the new (4.3.x) builders which allow a change of context: `QueryExec` for graph level, `QueryExecution.create` for model level (the associated builder also some legacy compatibility about setting timeouts).
   
   ```
           Graph graph = GraphFactory.createDefaultGraph();
   
           PropertyFunctionRegistry pfr = new PropertyFunctionRegistry();
           PropertyFunction pf = new version();
           pfr.put("urn:test:version", (x)->pf);
   
           Context cxt = ARQ.getContext().copy();
           PropertyFunctionRegistry.set(cxt, pfr);
   
           String qs = """
                   SELECT * { ?x <urn:test:version> ?y }
                   """;
           RowSet rowSet = QueryExec.graph(graph)
                   .context(cxt)
                   .query(qs)
                   .select();
           RowSetOps.out(rowSet);
   ```
   Unrelated: there is a problem with some system provided property functions. There is a hardwired translation in the code.
   ```
           Graph graph = GraphFactory.createDefaultGraph();
           Context cxt = ARQ.getContext().copy();    
           PropertyFunctionRegistry pfr = new PropertyFunctionRegistry();
           PropertyFunctionRegistry.set(cxt, pfr);
           String qs = """
                   PREFIX afn:     <http://jena.apache.org/ARQ/function#>
                   PREFIX apf:     <http://jena.apache.org/ARQ/property#>
                   SELECT * { ?x apf:version ?y }
                   """;
           RowSet rowSet = QueryExec.graph(graph)
                   .context(cxt)
                   .query(qs)
                   .select();
           RowSetOps.out(rowSet);
   ```
   doesn't work - `apf:version` is still a property function because `afn` and `apf` are hardwired in the registry code to map to "java:" URI which then will always happen. That's a bug.
   


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