/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hp.hpl.jena.sparql.engine.ref;
import com.hp.hpl.jena.query.Query ;
import com.hp.hpl.jena.sparql.algebra.Op ;
import com.hp.hpl.jena.sparql.algebra.Table ;
import com.hp.hpl.jena.sparql.algebra.Transform ;
import com.hp.hpl.jena.sparql.algebra.Transformer ;
import com.hp.hpl.jena.sparql.algebra.optimize.TransformPropertyFunction ;
import com.hp.hpl.jena.sparql.core.DatasetGraph ;
import com.hp.hpl.jena.sparql.core.Substitute ;
import com.hp.hpl.jena.sparql.engine.ExecutionContext ;
import com.hp.hpl.jena.sparql.engine.Plan ;
import com.hp.hpl.jena.sparql.engine.QueryEngineBase ;
import com.hp.hpl.jena.sparql.engine.QueryEngineFactory ;
import com.hp.hpl.jena.sparql.engine.QueryEngineRegistry ;
import com.hp.hpl.jena.sparql.engine.QueryIterator ;
import com.hp.hpl.jena.sparql.engine.binding.Binding ;
import com.hp.hpl.jena.sparql.engine.binding.BindingFactory ;
import com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorCheck ;
import com.hp.hpl.jena.sparql.engine.main.QC ;
import com.hp.hpl.jena.sparql.util.Context ;
/** "Reference" query engine - this simply executes the algebra expression as-is
* using a simple (non-scalable) execution strategy that follows the definition
* of SPARQL as closely as possible. The referenc query engine does provide the
* algebra extensions.
*/
public class QueryEngineRef extends QueryEngineBase
{
public QueryEngineRef(Op op, DatasetGraph dataset, Context context)
{ this(op, dataset, BindingFactory.root(), context) ; }
public QueryEngineRef(Op op, DatasetGraph dataset, Binding input, Context context)
{ super(op, dataset, input, context) ; }
protected QueryEngineRef(Query query, DatasetGraph dataset,
Binding input, Context context)
{
super(query, dataset, input, context) ;
}
@Override
protected Op modifyOp(Op op)
{
// Just property functions
Transform t = new TransformPropertyFunction(context) ;
op = Transformer.transform(t, op) ;
return op ;
}
@Override
public QueryIterator eval(Op op, DatasetGraph dsg, Binding binding, Context context)
{
if ( binding.vars().hasNext() )
op = Substitute.substitute(op, binding) ;
ExecutionContext execCxt = new ExecutionContext(context, dsg.getDefaultGraph(), dsg, QC.getFactory(context)) ;
Evaluator eval = EvaluatorFactory.create(execCxt) ;
Table table = Eval.eval(eval, op) ;
QueryIterator qIter = table.iterator(execCxt) ;
return QueryIteratorCheck.check(qIter, execCxt) ;
}
static public QueryEngineFactory getFactory() { return factory ; }
static public void register() { QueryEngineRegistry.addFactory(factory) ; }
static public void unregister() { QueryEngineRegistry.removeFactory(factory) ; }
private static QueryEngineFactory factory = new QueryEngineFactory()
{
@Override
public boolean accept(Query query, DatasetGraph dataset, Context context)
{ return true ; }
@Override
public Plan create(Query query, DatasetGraph dataset, Binding binding, Context context)
{
QueryEngineRef engine = new QueryEngineRef(query, dataset, binding, context) ;
return engine.getPlan() ;
}
@Override
public boolean accept(Op op, DatasetGraph dataset, Context context)
{ return true ; }
@Override
public Plan create(Op op, DatasetGraph dataset, Binding binding, Context context)
{
QueryEngineRef engine = new QueryEngineRef(op, dataset, binding, context) ;
return engine.getPlan() ;
}
} ;
}