/*
 * 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
 *
 *   https://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.
 *
 *   SPDX-License-Identifier: Apache-2.0
 */

package org.apache.jena.sparql.engine.iterator;

import java.util.HashSet;
import java.util.Set;

import org.apache.jena.sparql.engine.ExecutionContext;
import org.apache.jena.sparql.engine.QueryIterator;
import org.apache.jena.sparql.engine.binding.Binding;

/** Memory limited QueryIterDistinct */
public class QueryIterDistinctMem extends QueryIterDistinctReduced {
    private Set<Binding> seen = new HashSet<>();

    public QueryIterDistinctMem(QueryIterator iter, ExecutionContext context) {
        super(iter, context);
    }

    @Override
    protected void closeSubIterator() {
        seen = null;
        super.closeSubIterator();
    }

    @Override
    protected boolean isFreshSighting(Binding binding) {
        if ( seen.contains(binding) )
            return false;
        seen.add(binding);
        return true;
    }
}
