/*
 * 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.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators;


import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.data.DataBag;
import org.apache.pig.data.Tuple;
import org.apache.pig.impl.plan.OperatorKey;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.plans.PhyPlanVisitor;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.plans.PhyPlanVisitor;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.PhysicalOperator;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.Result;
import org.apache.pig.impl.plan.VisitorException;

/**
 * A base class for all types of expressions. All expression
 * operators must extend this class.
 *
 */

public abstract class ExpressionOperator extends PhysicalOperator {
    private static final long serialVersionUID = 1L;
    protected Log log = LogFactory.getLog(getClass());
    
    public ExpressionOperator(OperatorKey k) {
        this(k,-1);
    }

    public ExpressionOperator(OperatorKey k, int rp) {
        super(k, rp);
    }
    
    @Override
    public boolean supportsMultipleOutputs() {
        return false;
    }
    
    @Override
    public Result getNext(DataBag db) throws ExecException {
        return new Result();
    }
    
    public abstract void visit(PhyPlanVisitor v) throws VisitorException;

    /**
     * Make a deep copy of this operator.  This is declared here to make it
     * possible to call clone on ExpressionOperators.
     * @throws CloneNotSupportedException
     */
    @Override
    public ExpressionOperator clone() throws CloneNotSupportedException {
        String s = new String("This expression operator does not " +
            "implement clone.");
        log.error(s);
        throw new CloneNotSupportedException(s);
    }


}