CachingPF.java

/*
 * 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 org.apache.jena.tdb.migrate;

import java.util.ArrayList;
import java.util.List;

import org.apache.jena.graph.Node ;
import org.apache.jena.sparql.engine.ExecutionContext ;
import org.apache.jena.sparql.engine.QueryIterator ;
import org.apache.jena.sparql.engine.binding.Binding ;
import org.apache.jena.sparql.engine.iterator.QueryIterPlainWrapper ;
import org.apache.jena.sparql.pfunction.PropFuncArg ;
import org.apache.jena.sparql.pfunction.PropertyFunction ;

/** A Property function that ignores it's arguments but reads and caches it's inputs */
public class CachingPF implements PropertyFunction
{

    @Override
    public void build(PropFuncArg argSubject, Node predicate, PropFuncArg argObject, ExecutionContext execCxt)
    {}

    //Override
    @Override
    public QueryIterator exec(QueryIterator input, PropFuncArg argSubject, Node predicate, PropFuncArg argObject,
                              ExecutionContext execCxt)
    {
        List<Binding> bindings = new ArrayList<>() ;
        for ( ; input.hasNext() ; )
            bindings.add(input.nextBinding()) ;
        return new QueryIterPlainWrapper(bindings.iterator(), execCxt) ;
    }

}