src/org/apache/pig/backend/hadoop/executionengine/physicalLayer/expressionOperators/Divide.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 java.math.BigDecimal;
import java.math.BigInteger;
import java.math.RoundingMode;

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

public class Divide extends BinaryExpressionOperator {

    /**
     *
     */
    private static final long serialVersionUID = 1L;
    public static final short BIGDECIMAL_MINIMAL_SCALE = 6;
    private static final Log LOG = LogFactory.getLog(Divide.class);

    public Divide(OperatorKey k) {
        super(k);
    }

    public Divide(OperatorKey k, int rp) {
        super(k, rp);
    }

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

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

    /*
     * This method is used to invoke the appropriate method, as Java does not provide generic
     * dispatch for it.
     */
    protected Number divide(Number a, Number b, byte dataType) throws ExecException {
        switch (dataType) {
        case DataType.DOUBLE:
            return Double.valueOf((Double) a / (Double) b);
        case DataType.INTEGER:
            return Integer.valueOf((Integer) a / (Integer) b);
        case DataType.LONG:
            return Long.valueOf((Long) a / (Long) b);
        case DataType.FLOAT:
            return Float.valueOf((Float) a / (Float) b);
        case DataType.BIGINTEGER:
            return ((BigInteger) a).divide((BigInteger) b);
        case DataType.BIGDECIMAL:
            return bigDecimalDivideWithScale(a, b);
        default:
            throw new ExecException("called on unsupported Number class " + DataType.findTypeName(dataType));
        }
    }

    private Number bigDecimalDivideWithScale(Number a, Number b) {
        // Using same result scaling as Hive. See Arithmetic Rules:
        //   https://cwiki.apache.org/confluence/download/attachments/27362075/Hive_Decimal_Precision_Scale_Support.pdf
        int resultScale = Math.max(BIGDECIMAL_MINIMAL_SCALE, ((BigDecimal)a).scale() + ((BigDecimal)b).precision() + 1);
        if (LOG.isDebugEnabled()) {
            LOG.debug("For bigdecimal divide: using " + resultScale + " as result scale.");
        }
        return ((BigDecimal)a).divide((BigDecimal)b, resultScale, RoundingMode.HALF_UP);
    }

    /*
     * This method is used to invoke the appropriate method, as Java does not provide generic
     * dispatch for it.
     */
    protected boolean equalsZero(Number a, byte dataType) throws ExecException {
        switch (dataType) {
        case DataType.DOUBLE:
            return ((Double) a).equals(0.0);
        case DataType.INTEGER:
            return ((Integer) a).equals(0);
        case DataType.LONG:
            return ((Long) a).equals(0L);
        case DataType.FLOAT:
            return ((Float) a).equals(0.0f);
        case DataType.BIGINTEGER:
            return BigInteger.ZERO.equals((BigInteger) a);
        case DataType.BIGDECIMAL:
            return ((BigDecimal) a).signum() == 0;
        default:
            throw new ExecException("Called on unsupported Number class " + DataType.findTypeName(dataType));
        }
    }

    protected Result genericGetNext(byte dataType) throws ExecException {
        Result r = accumChild(null, dataType);
        if (r != null) {
            return r;
        }


        byte status;
        Result res;
        res = lhs.getNext(dataType);
        status = res.returnStatus;
        if(status != POStatus.STATUS_OK || res.result == null) {
            return res;
        }
        Number left = (Number) res.result;

        res = rhs.getNext(dataType);
        status = res.returnStatus;
        if(status != POStatus.STATUS_OK || res.result == null) {
            return res;
        }
        Number right = (Number) res.result;

        if (equalsZero(right, dataType)) {
            if(pigLogger != null) {
                pigLogger.warn(this, "Divide by zero. Converting it to NULL.", PigWarning.DIVIDE_BY_ZERO);
            }
            res.result = null;
        } else {
            res.result = divide(left, right, dataType);
        }
        return res;
    }

    @Override
    public Result getNextDouble() throws ExecException {
        return genericGetNext(DataType.DOUBLE);
    }

    @Override
    public Result getNextFloat() throws ExecException {
        return genericGetNext(DataType.FLOAT);

    }

    @Override
    public Result getNextInteger() throws ExecException {
        return genericGetNext(DataType.INTEGER);
    }

    @Override
    public Result getNextLong() throws ExecException {
        return genericGetNext(DataType.LONG);
    }

    @Override
    public Result getNextBigInteger() throws ExecException {
        return genericGetNext(DataType.BIGINTEGER);
    }

    @Override
    public Result getNextBigDecimal() throws ExecException {
        return genericGetNext(DataType.BIGDECIMAL);
    }

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


}