AccumulatorDistinctAll.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.sparql.expr.aggregate;

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

import org.apache.jena.sparql.engine.binding.Binding ;
import org.apache.jena.sparql.function.FunctionEnv ;

/** Accumulator that only passes down the first unique binding */
abstract class AccumulatorDistinctAll implements Accumulator
{
    // COUNT(DISTINCT *)
    private final Set<Binding> rows = new HashSet<>() ;
    
    @Override
    final public void accumulate(Binding binding, FunctionEnv functionEnv)
    {
        if ( rows.contains(binding) )
            return ;
        rows.add(binding) ;
        accumulateDistinct(binding, functionEnv) ;
    }
    
    protected abstract void accumulateDistinct(Binding binding, FunctionEnv functionEnv) ;
}