spork-master/src/org/apache/pig/backend/hadoop/executionengine/physicalLayer/expressionOperators/POOr.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.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators;

import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.POStatus;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.Result;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.plans.PhyPlanVisitor;
import org.apache.pig.data.DataType;
import org.apache.pig.impl.plan.NodeIdGenerator;
import org.apache.pig.impl.plan.OperatorKey;
import org.apache.pig.impl.plan.VisitorException;

/**
 * Boolean or operator.
 */

public class POOr extends BinaryComparisonOperator {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    public POOr(OperatorKey k) {
        this(k, -1);
    }

    public POOr(OperatorKey k, int rp) {
        super(k, rp);
        resultType = DataType.BOOLEAN;
    }

    @Override
    public void visit(PhyPlanVisitor v) throws VisitorException {
        v.visitOr(this);
    }

    @Override
    public String name() {
        return "Or" + "[" + DataType.findTypeName(resultType) + "]" +" - " + mKey.toString();
    }

    @Override
    public Result getNextBoolean() throws ExecException {
        Result r = accumChild(null, DataType.BOOLEAN);
        if (r != null) {
            return r;
        }
        
        Result left;
        left = lhs.getNextBoolean();
        // pass on ERROR, EOP, and NULL
        if (left.returnStatus != POStatus.STATUS_OK) {
            return left;
        }
        
        // truth table for OR 
        // t = true, n = null, f = false
        //    OR   t n f
        // 1) t    t t t
        // 2) n    t n n
        // 3) f    t n f
        
        // Short circuit. if lhs is true, return true - ROW 1 above is handled with this
        boolean returnLeft = false;
        if (left.result != null && ((Boolean)left.result).booleanValue()) {
          if (illustrator == null)
              return left;
          
          illustratorMarkup(null, left.result, 0);
          returnLeft = true;;
        }
        
        Result right = rhs.getNextBoolean();
        if (returnLeft)
            return left;

        // pass on ERROR, EOP, and NULL
        if (right.returnStatus != POStatus.STATUS_OK) {
            return right;
        }
        
        // if the lhs is null and rhs is false - return null , in all other cases, we can
        // just return rhs - ROW 2 and ROW 3 above
        if(left.result == null && right.result != null && !((Boolean)right.result).booleanValue()) {
            return left;
        }
        
        // No matter what, what we get from the right side is what we'll
        // return, null, true, or false.
        if (right.result != null)
            illustratorMarkup(null, right.result, (Boolean) right.result ? 0 : 1);
        return right;
    }

    @Override
    public POOr clone() throws CloneNotSupportedException {
        POOr clone = new POOr(new OperatorKey(mKey.scope, 
            NodeIdGenerator.getGenerator().getNextNodeId(mKey.scope)));
        clone.cloneHelper(this);
        return clone;
    }
}
