spork-master/src/org/apache/pig/newplan/logical/relational/LogToPhyTranslationVisitor.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.newplan.logical.relational;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Deque;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Random;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.pig.FuncSpec;
import org.apache.pig.PigException;
import org.apache.pig.ResourceSchema;
import org.apache.pig.StoreResources;
import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.LogicalToPhysicalTranslatorException;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.PhysicalOperator;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.ConstantExpression;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POProject;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserComparisonFunc;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.plans.PhysicalPlan;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POCollectedGroup;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POCounter;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POCross;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.PODistinct;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POFRJoin;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POFilter;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POGlobalRearrange;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POLimit;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POLoad;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POLocalRearrange;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POMergeCogroup;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POMergeJoin;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.PONative;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POPackage;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.PORank;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POSkewedJoin;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POSort;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POSplit;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POStore;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POStream;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POUnion;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.Packager.PackageType;
import org.apache.pig.data.DataType;
import org.apache.pig.data.SchemaTupleClassGenerator.GenContext;
import org.apache.pig.data.SchemaTupleFrontend;
import org.apache.pig.data.Tuple;
import org.apache.pig.data.TupleFactory;
import org.apache.pig.impl.PigContext;
import org.apache.pig.impl.builtin.GFCross;
import org.apache.pig.impl.io.FileLocalizer;
import org.apache.pig.impl.io.FileSpec;
import org.apache.pig.impl.logicalLayer.FrontendException;
import org.apache.pig.impl.logicalLayer.schema.Schema;
import org.apache.pig.impl.logicalLayer.schema.Schema.FieldSchema;
import org.apache.pig.impl.plan.NodeIdGenerator;
import org.apache.pig.impl.plan.OperatorKey;
import org.apache.pig.impl.plan.PlanException;
import org.apache.pig.impl.plan.VisitorException;
import org.apache.pig.impl.util.CompilerUtils;
import org.apache.pig.impl.util.LinkedMultiMap;
import org.apache.pig.impl.util.MultiMap;
import org.apache.pig.impl.util.Utils;
import org.apache.pig.newplan.DependencyOrderWalker;
import org.apache.pig.newplan.Operator;
import org.apache.pig.newplan.OperatorPlan;
import org.apache.pig.newplan.PlanWalker;
import org.apache.pig.newplan.ReverseDependencyOrderWalkerWOSeenChk;
import org.apache.pig.newplan.SubtreeDependencyOrderWalker;
import org.apache.pig.newplan.logical.Util;
import org.apache.pig.newplan.logical.expression.ExpToPhyTranslationVisitor;
import org.apache.pig.newplan.logical.expression.LogicalExpressionPlan;
import org.apache.pig.newplan.logical.expression.ProjectExpression;
import org.apache.pig.parser.SourceLocation;

public class LogToPhyTranslationVisitor extends LogicalRelationalNodesVisitor {
    private static final Log LOG = LogFactory.getLog(LogToPhyTranslationVisitor.class);

    public LogToPhyTranslationVisitor(OperatorPlan plan) throws FrontendException {
        super(plan, new DependencyOrderWalker(plan));
        currentPlan = new PhysicalPlan();
        logToPhyMap = new HashMap<Operator, PhysicalOperator>();
        currentPlans = new LinkedList<PhysicalPlan>();
    }

    protected Map<Operator, PhysicalOperator> logToPhyMap;

    protected Deque<PhysicalPlan> currentPlans;

    protected PhysicalPlan currentPlan;

    protected NodeIdGenerator nodeGen = NodeIdGenerator.getGenerator();

    protected PigContext pc;

    public void setPigContext(PigContext pc) {
        this.pc = pc;
    }

    public Map<Operator, PhysicalOperator> getLogToPhyMap() {
        return logToPhyMap;
    }

    public PhysicalPlan getPhysicalPlan() {
        return currentPlan;
    }

    @Override
    public void visit(LOLoad loLoad) throws FrontendException {
        String scope = DEFAULT_SCOPE;
        // The last parameter here is set to true as we assume all files are
        // splittable due to LoadStore Refactor
        POLoad load = new POLoad(new OperatorKey(scope, nodeGen
                .getNextNodeId(scope)), loLoad.getLoadFunc());
        load.addOriginalLocation(loLoad.getAlias(), loLoad.getLocation());
        load.setLFile(loLoad.getFileSpec());
        load.setPc(pc);
        load.setResultType(DataType.BAG);
        load.setSignature(loLoad.getSignature());
        load.setLimit(loLoad.getLimit());
        load.setIsTmpLoad(loLoad.isTmpLoad());
        load.setCacheFiles(loLoad.getLoadFunc().getCacheFiles());
        load.setShipFiles(loLoad.getLoadFunc().getShipFiles());

        currentPlan.add(load);
        logToPhyMap.put(loLoad, load);

        // Load is typically a root operator, but in the multiquery
        // case it might have a store as a predecessor.
        List<Operator> op = loLoad.getPlan().getPredecessors(loLoad);
        PhysicalOperator from;

        if(op != null) {
            from = logToPhyMap.get(op.get(0));
            try {
                currentPlan.connect(from, load);
            } catch (PlanException e) {
                int errCode = 2015;
                String msg = "Invalid physical operators in the physical plan" ;
                throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
            }
        }
    }

    @Override
    public void visit(LONative loNative) throws FrontendException{
        String scope = DEFAULT_SCOPE;

        PONative poNative = new PONative(new OperatorKey(scope, nodeGen
                .getNextNodeId(scope)));
        poNative.addOriginalLocation(loNative.getAlias(), loNative.getLocation());
        poNative.setNativeMRjar(loNative.getNativeMRJar());
        poNative.setParams(loNative.getParams());
        poNative.setResultType(DataType.BAG);

        logToPhyMap.put(loNative, poNative);
        currentPlan.add(poNative);

        List<Operator> op = loNative.getPlan().getPredecessors(loNative);

        PhysicalOperator from;
        if(op != null) {
            from = logToPhyMap.get(op.get(0));
        } else {
            int errCode = 2051;
            String msg = "Did not find a predecessor for Native." ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG);
        }

        try {
            currentPlan.connect(from, poNative);
        } catch (PlanException e) {
            int errCode = 2015;
            String msg = "Invalid physical operators in the physical plan" ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
        }

    }

    @Override
    public void visit(LOFilter filter) throws FrontendException {
        String scope = DEFAULT_SCOPE;
        //        System.err.println("Entering Filter");
        POFilter poFilter = new POFilter(new OperatorKey(scope, nodeGen
                .getNextNodeId(scope)), filter.getRequestedParallelism());
        poFilter.addOriginalLocation(filter.getAlias(), filter.getLocation());
        poFilter.setResultType(DataType.BAG);
        currentPlan.add(poFilter);
        logToPhyMap.put(filter, poFilter);
        currentPlans.push(currentPlan);

        currentPlan = new PhysicalPlan();

        //        PlanWalker childWalker = currentWalker
        //                .spawnChildWalker(filter.getFilterPlan());
        PlanWalker childWalker = new ReverseDependencyOrderWalkerWOSeenChk(filter.getFilterPlan());
        pushWalker(childWalker);
        //currentWalker.walk(this);
        currentWalker.walk(
                new ExpToPhyTranslationVisitor( currentWalker.getPlan(),
                        childWalker, filter, currentPlan, logToPhyMap ) );
        popWalker();

        poFilter.setPlan(currentPlan);
        currentPlan = currentPlans.pop();

        List<Operator> op = filter.getPlan().getPredecessors(filter);

        PhysicalOperator from;
        if(op != null) {
            from = logToPhyMap.get(op.get(0));
        } else {
            int errCode = 2051;
            String msg = "Did not find a predecessor for Filter." ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG);
        }

        try {
            currentPlan.connect(from, poFilter);
        } catch (PlanException e) {
            int errCode = 2015;
            String msg = "Invalid physical operators in the physical plan" ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
        }

        translateSoftLinks(filter);
        //        System.err.println("Exiting Filter");
    }

    @Override
    public void visit(LOSort sort) throws FrontendException {
        String scope = DEFAULT_SCOPE;
        List<LogicalExpressionPlan> logPlans = sort.getSortColPlans();
        List<PhysicalPlan> sortPlans = new ArrayList<PhysicalPlan>(logPlans.size());

        // convert all the logical expression plans to physical expression plans
        currentPlans.push(currentPlan);
        for (LogicalExpressionPlan plan : logPlans) {
            currentPlan = new PhysicalPlan();
            PlanWalker childWalker = new ReverseDependencyOrderWalkerWOSeenChk(plan);
            pushWalker(childWalker);
            childWalker.walk(new ExpToPhyTranslationVisitor( currentWalker.getPlan(),
                    childWalker, sort, currentPlan, logToPhyMap));
            sortPlans.add(currentPlan);
            popWalker();
        }
        currentPlan = currentPlans.pop();

        // get the physical operator for sort
        POSort poSort;
        if (sort.getUserFunc() == null) {
            poSort = new POSort(new OperatorKey(scope, nodeGen
                    .getNextNodeId(scope)), sort.getRequestedParallelism(), null,
                    sortPlans, sort.getAscendingCols(), null);
        } else {
            POUserComparisonFunc comparator = new POUserComparisonFunc(new OperatorKey(
                    scope, nodeGen.getNextNodeId(scope)), sort
                    .getRequestedParallelism(), null, sort.getUserFunc());
            poSort = new POSort(new OperatorKey(scope, nodeGen
                    .getNextNodeId(scope)), sort.getRequestedParallelism(), null,
                    sortPlans, sort.getAscendingCols(), comparator);
        }
        poSort.addOriginalLocation(sort.getAlias(), sort.getLocation());
        poSort.setLimit(sort.getLimit());
        // sort.setRequestedParallelism(s.getType());
        logToPhyMap.put(sort, poSort);
        currentPlan.add(poSort);
        List<Operator> op = sort.getPlan().getPredecessors(sort);
        PhysicalOperator from;

        if(op != null) {
            from = logToPhyMap.get(op.get(0));
        } else {
            int errCode = 2051;
            String msg = "Did not find a predecessor for Sort." ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG);
        }

        try {
            currentPlan.connect(from, poSort);
        } catch (PlanException e) {
            int errCode = 2015;
            String msg = "Invalid physical operators in the physical plan" ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
        }

        poSort.setResultType(DataType.BAG);
    }

    /**
     * Transformation from Logical to Physical Plan involves the following steps:
     * First, it is generated a random number which will link a POCounter within a PORank.
     * On this way, avoiding possible collisions on parallel rank operations.
     * Then, if it is row number mode:
     * <pre>
     * In case of a RANK operation (row number mode), are used two steps:
     *   1.- Each tuple is counted sequentially on each mapper, and are produced global counters
     *   2.- Global counters are gathered and summed, each tuple calls to the respective counter value
     *       in order to calculate the corresponding rank value.
     * </pre>
     * or not:
     * <pre>
     * In case of a RANK BY operation, then are necessary five steps:
     *   1.- Group by the fields involved on the rank operation: POPackage
     *   2.- In case of multi-fields, the key (group field) is flatten: POForEach
     *   3.- Sort operation by the fields available after flattening: POSort
     *   4.- Each group is sequentially counted on each mapper through a global counter: POCounter
     *   5.- Global counters are summed and passed to the rank operation: PORank
     * </pre>
     * @param loRank describe if the rank operation is on a row number mode
     * or is rank by (dense or not)
     **/
    @Override
    public void visit(LORank loRank) throws FrontendException {
        String scope = DEFAULT_SCOPE;
        PORank poRank;
        POCounter poCounter;

        Random randomGenerator = new Random();
        Long operationID = Math.abs(randomGenerator.nextLong());

        try {
            // Physical operations for RANK operator:
            // In case of a RANK BY operation, then are necessary five steps:
            //   1.- Group by the fields involved on the rank operation: POPackage
            //   2.- In case of multi-fields, the key (group field) is flatten: POForEach
            //   3.- Sort operation by the fields available after flattening: POSort
            //   4.- Each group is sequentially counted on each mapper through a global counter: POCounter
            //   5.- Global counters are summed and passed to the rank operation: PORank
            if(!loRank.isRowNumber()) {

                boolean[] flags = {false};

                MultiMap<Integer, LogicalExpressionPlan> expressionPlans = new MultiMap<Integer, LogicalExpressionPlan>();
                for(int i = 0 ; i < loRank.getRankColPlans().size() ; i++)
                    expressionPlans.put(i,loRank.getRankColPlans());

                POPackage poPackage = compileToLR_GR_PackTrio(loRank, null, flags, expressionPlans);
                poPackage.getPkgr().setPackageType(PackageType.GROUP);
                translateSoftLinks(loRank);

                List<Boolean> flattenLst = Arrays.asList(true, false);

                PhysicalPlan fep1 = new PhysicalPlan();
                POProject feproj1 = new POProject(new OperatorKey(scope, nodeGen.getNextNodeId(scope)), -1);
                feproj1.addOriginalLocation(loRank.getAlias(), loRank.getLocation());
                feproj1.setColumn(0);
                feproj1.setResultType(poPackage.getPkgr().getKeyType());
                feproj1.setStar(false);
                feproj1.setOverloaded(false);
                fep1.add(feproj1);


                PhysicalPlan fep2 = new PhysicalPlan();
                POProject feproj2 = new POProject(new OperatorKey(scope, nodeGen.getNextNodeId(scope)), -1);
                feproj2.addOriginalLocation(loRank.getAlias(), loRank.getLocation());
                feproj2.setColumn(1);
                feproj2.setResultType(DataType.BAG);
                feproj2.setStar(false);
                feproj2.setOverloaded(false);
                fep2.add(feproj2);
                List<PhysicalPlan> fePlans = Arrays.asList(fep1, fep2);

                POForEach poForEach = new POForEach(new OperatorKey(scope, nodeGen.getNextNodeId(scope)), -1, fePlans, flattenLst);

                List<LogicalExpressionPlan> rankPlans = loRank.getRankColPlans();
                byte[] newTypes = new byte[rankPlans.size()];

                for(int i = 0; i < rankPlans.size(); i++) {
                    LogicalExpressionPlan loep = rankPlans.get(i);
                    Iterator<Operator> inpOpers = loep.getOperators();

                    while(inpOpers.hasNext()) {
                        Operator oper = inpOpers.next();
                        newTypes[i] = ((ProjectExpression) oper).getType();
                    }
                }

                List<PhysicalPlan> newPhysicalPlan = new ArrayList<PhysicalPlan>();
                List<Boolean> newOrderPlan = new ArrayList<Boolean>();

                for(int i = 0; i < loRank.getRankColPlans().size(); i++) {
                    PhysicalPlan fep3 = new PhysicalPlan();
                    POProject feproj3 = new POProject(new OperatorKey(scope, nodeGen.getNextNodeId(scope)), -1);
                    feproj3.addOriginalLocation(loRank.getAlias(), loRank.getLocation());
                    feproj3.setColumn(i);
                    feproj3.setResultType(newTypes[i]);
                    feproj3.setStar(false);
                    feproj3.setOverloaded(false);
                    fep3.add(feproj3);

                    newPhysicalPlan.add(fep3);
                    newOrderPlan.add(loRank.getAscendingCol().get(i));
                }

                POSort poSort;
                poSort = new POSort(new OperatorKey(scope, nodeGen
                        .getNextNodeId(scope)), -1, null,
                        newPhysicalPlan, newOrderPlan, null);
                poSort.addOriginalLocation(loRank.getAlias(), loRank.getLocation());


                poCounter = new POCounter(
                        new OperatorKey(scope, nodeGen
                                .getNextNodeId(scope)), -1 , null,
                                newPhysicalPlan, newOrderPlan);

                poCounter.addOriginalLocation(loRank.getAlias(), loRank.getLocation());
                poCounter.setResultType(DataType.TUPLE);
                poCounter.setIsRowNumber(loRank.isRowNumber());
                poCounter.setIsDenseRank(loRank.isDenseRank());
                poCounter.setOperationID(String.valueOf(operationID));

                poRank = new PORank(
                        new OperatorKey(scope, nodeGen
                                .getNextNodeId(scope)), -1 , null,
                                newPhysicalPlan, newOrderPlan);

                poRank.addOriginalLocation(loRank.getAlias(), loRank.getLocation());
                poRank.setResultType(DataType.TUPLE);
                poRank.setOperationID(String.valueOf(operationID));

                List<Boolean> flattenLst2 = Arrays.asList(false, true);

                PhysicalPlan fep12 = new PhysicalPlan();
                POProject feproj12 = new POProject(new OperatorKey(scope, nodeGen.getNextNodeId(scope)), -1);
                feproj12.addOriginalLocation(loRank.getAlias(), loRank.getLocation());
                feproj12.setColumn(0);
                feproj12.setResultType(DataType.LONG);
                feproj12.setStar(false);
                feproj12.setOverloaded(false);
                fep12.add(feproj12);


                PhysicalPlan fep22 = new PhysicalPlan();
                POProject feproj22 = new POProject(new OperatorKey(scope, nodeGen.getNextNodeId(scope)), -1);
                feproj22.addOriginalLocation(loRank.getAlias(), loRank.getLocation());
                feproj22.setColumn(loRank.getRankColPlans().size()+1);
                feproj22.setResultType(DataType.BAG);
                feproj22.setStar(false);
                feproj22.setOverloaded(false);
                fep22.add(feproj22);
                List<PhysicalPlan> fePlans2 = Arrays.asList(fep12, fep22);

                POForEach poForEach2 = new POForEach(new OperatorKey(scope, nodeGen.getNextNodeId(scope)), -1, fePlans2, flattenLst2);

                currentPlan.add(poForEach);
                currentPlan.add(poSort);
                currentPlan.add(poCounter);
                currentPlan.add(poRank);
                currentPlan.add(poForEach2);

                try {
                    currentPlan.connect(poPackage, poForEach);
                    currentPlan.connect(poForEach, poSort);
                    currentPlan.connect(poSort, poCounter);
                    currentPlan.connect(poCounter, poRank);
                    currentPlan.connect(poRank, poForEach2);
                } catch (PlanException e) {
                    throw new LogicalToPhysicalTranslatorException(e.getMessage(),e.getErrorCode(),e.getErrorSource(),e);
                }

                logToPhyMap.put(loRank, poForEach2);

                // In case of a RANK operation, are used two steps:
                //   1.- Each tuple is counted sequentially on each mapper, and are produced global counters
                //   2.- Global counters are gathered and summed, each tuple calls to the respective counter value
                //       in order to calculate the corresponding rank value.
            } else {

                List<LogicalExpressionPlan> logPlans = loRank.getRankColPlans();
                List<PhysicalPlan> rankPlans = new ArrayList<PhysicalPlan>(logPlans.size());

                // convert all the logical expression plans to physical expression plans
                currentPlans.push(currentPlan);
                for (LogicalExpressionPlan plan : logPlans) {
                    currentPlan = new PhysicalPlan();
                    PlanWalker childWalker = new ReverseDependencyOrderWalkerWOSeenChk(plan);
                    pushWalker(childWalker);
                    childWalker.walk(new ExpToPhyTranslationVisitor( currentWalker.getPlan(),
                            childWalker, loRank, currentPlan, logToPhyMap));
                    rankPlans.add(currentPlan);
                    popWalker();
                }
                currentPlan = currentPlans.pop();



                poCounter = new POCounter(
                        new OperatorKey(scope, nodeGen
                                .getNextNodeId(scope)), -1 , null,
                                rankPlans, loRank.getAscendingCol());

                poCounter.addOriginalLocation(loRank.getAlias(), loRank.getLocation());
                poCounter.setResultType(DataType.TUPLE);
                poCounter.setIsRowNumber(loRank.isRowNumber());
                poCounter.setIsDenseRank(loRank.isDenseRank());
                poCounter.setOperationID(String.valueOf(operationID));

                poRank = new PORank(
                        new OperatorKey(scope, nodeGen
                                .getNextNodeId(scope)), -1 , null,
                                rankPlans, loRank.getAscendingCol());

                poRank.addOriginalLocation(loRank.getAlias(), loRank.getLocation());
                poRank.setResultType(DataType.TUPLE);
                poRank.setOperationID(String.valueOf(operationID));

                currentPlan.add(poCounter);
                currentPlan.add(poRank);

                List<Operator> op = loRank.getPlan().getPredecessors(loRank);
                PhysicalOperator from;

                if(op != null) {
                    from = logToPhyMap.get(op.get(0));
                } else {
                    int errCode = 2051;
                    String msg = "Did not find a predecessor for Rank." ;
                    throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG);
                }

                currentPlan.connect(from, poCounter);
                currentPlan.connect(poCounter, poRank);

                logToPhyMap.put(loRank, poRank);
            }

        } catch (PlanException e) {
            int errCode = 2015;
            String msg = "Invalid physical operators in the physical plan" ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
        }

    }

    @Override
    public void visit(LOCross cross) throws FrontendException {
        String scope = DEFAULT_SCOPE;
        List<Operator> inputs = cross.getPlan().getPredecessors(cross);
                if (cross.isNested()) {
            POCross physOp = new POCross(new OperatorKey(scope,nodeGen.getNextNodeId(scope)), cross.getRequestedParallelism());
            physOp.addOriginalLocation(physOp.getAlias(), physOp.getOriginalLocations());
            currentPlan.add(physOp);
            physOp.setResultType(DataType.BAG);
            logToPhyMap.put(cross, physOp);
            for (Operator op : cross.getPlan().getPredecessors(cross)) {
                PhysicalOperator from = logToPhyMap.get(op);
                try {
                    currentPlan.connect(from, physOp);
                } catch (PlanException e) {
                    int errCode = 2015;
                    String msg = "Invalid physical operators in the physical plan" ;
                    throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
                }
            }
        } else {
            POGlobalRearrange poGlobal = new POGlobalRearrange(new OperatorKey(
                    scope, nodeGen.getNextNodeId(scope)), cross
                    .getRequestedParallelism());
            poGlobal.addOriginalLocation(cross.getAlias(), cross.getLocation());
            POPackage poPackage = new POPackage(new OperatorKey(scope, nodeGen
                    .getNextNodeId(scope)), cross.getRequestedParallelism());
            poGlobal.addOriginalLocation(cross.getAlias(), cross.getLocation());
            poGlobal.setCross(true);
            currentPlan.add(poGlobal);
            currentPlan.add(poPackage);

            int count = 0;

            try {
                currentPlan.connect(poGlobal, poPackage);
                List<Boolean> flattenLst = Arrays.asList(true, true);

                for (Operator op : inputs) {
                    PhysicalPlan fep1 = new PhysicalPlan();
                    ConstantExpression ce1 = new ConstantExpression(new OperatorKey(scope, nodeGen.getNextNodeId(scope)),cross.getRequestedParallelism());
                    ce1.setValue(inputs.size());
                    ce1.setResultType(DataType.INTEGER);
                    fep1.add(ce1);

                    ConstantExpression ce2 = new ConstantExpression(new OperatorKey(scope, nodeGen.getNextNodeId(scope)),cross.getRequestedParallelism());
                    ce2.setValue(count);
                    ce2.setResultType(DataType.INTEGER);
                    fep1.add(ce2);
                    /*Tuple ce1val = TupleFactory.getInstance().newTuple(2);
                    ce1val.set(0,inputs.size());
                    ce1val.set(1,count);
                    ce1.setValue(ce1val);
                    ce1.setResultType(DataType.TUPLE);*/

                    POUserFunc gfc = new POUserFunc(new OperatorKey(scope, nodeGen.getNextNodeId(scope)),cross.getRequestedParallelism(),
                            Arrays.asList((PhysicalOperator)ce1,(PhysicalOperator)ce2), new FuncSpec(GFCross.class.getName()
                            + "('" + poGlobal.getOperatorKey().toString() + "')"));
                    gfc.addOriginalLocation(cross.getAlias(), cross.getLocation());
                    gfc.setResultType(DataType.BAG);
                    fep1.addAsLeaf(gfc);
                    gfc.setInputs(Arrays.asList((PhysicalOperator)ce1,(PhysicalOperator)ce2));
                    /*fep1.add(gfc);
                    fep1.connect(ce1, gfc);
                    fep1.connect(ce2, gfc);*/

                    PhysicalPlan fep2 = new PhysicalPlan();
                    POProject feproj = new POProject(new OperatorKey(scope, nodeGen.getNextNodeId(scope)), cross.getRequestedParallelism());
                    feproj.addOriginalLocation(cross.getAlias(), cross.getLocation());
                    feproj.setResultType(DataType.TUPLE);
                    feproj.setStar(true);
                    feproj.setOverloaded(false);
                    fep2.add(feproj);
                    List<PhysicalPlan> fePlans = Arrays.asList(fep1, fep2);

                    POForEach fe = new POForEach(new OperatorKey(scope, nodeGen.getNextNodeId(scope)), cross.getRequestedParallelism(), fePlans, flattenLst );
                    fe.setMapSideOnly(true);
                    fe.addOriginalLocation(cross.getAlias(), cross.getLocation());
                    currentPlan.add(fe);
                    currentPlan.connect(logToPhyMap.get(op), fe);

                    POLocalRearrange physOp = new POLocalRearrange(new OperatorKey(
                            scope, nodeGen.getNextNodeId(scope)), cross
                            .getRequestedParallelism());
                    physOp.addOriginalLocation(cross.getAlias(), cross.getLocation());
                    List<PhysicalPlan> lrPlans = new ArrayList<PhysicalPlan>();
                    for(int i=0;i<inputs.size();i++){
                        PhysicalPlan lrp1 = new PhysicalPlan();
                        POProject lrproj1 = new POProject(new OperatorKey(scope, nodeGen.getNextNodeId(scope)), cross.getRequestedParallelism(), i);
                        lrproj1.addOriginalLocation(cross.getAlias(), cross.getLocation());
                        lrproj1.setOverloaded(false);
                        lrproj1.setResultType(DataType.INTEGER);
                        lrp1.add(lrproj1);
                        lrPlans.add(lrp1);
                    }

                    physOp.setCross(true);
                    physOp.setIndex(count++);
                    physOp.setKeyType(DataType.TUPLE);
                    physOp.setPlans(lrPlans);
                    physOp.setResultType(DataType.TUPLE);

                    currentPlan.add(physOp);
                    currentPlan.connect(fe, physOp);
                    currentPlan.connect(physOp, poGlobal);
                }
            } catch (PlanException e1) {
                int errCode = 2015;
                String msg = "Invalid physical operators in the physical plan" ;
                throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e1);
            } catch (ExecException e) {
                int errCode = 2058;
                String msg = "Unable to set index on newly create POLocalRearrange.";
                throw new VisitorException(msg, errCode, PigException.BUG, e);
            }

            poPackage.getPkgr().setKeyType(DataType.TUPLE);
            poPackage.setResultType(DataType.TUPLE);
            poPackage.setNumInps(count);
            boolean inner[] = new boolean[count];
            for (int i=0;i<count;i++) {
                inner[i] = true;
            }
            poPackage.getPkgr().setInner(inner);

            List<PhysicalPlan> fePlans = new ArrayList<PhysicalPlan>();
            List<Boolean> flattenLst = new ArrayList<Boolean>();
            for(int i=1;i<=count;i++){
                PhysicalPlan fep1 = new PhysicalPlan();
                POProject feproj1 = new POProject(new OperatorKey(scope, nodeGen.getNextNodeId(scope)), cross.getRequestedParallelism(), i);
                feproj1.addOriginalLocation(cross.getAlias(), cross.getLocation());
                feproj1.setResultType(DataType.BAG);
                feproj1.setOverloaded(false);
                fep1.add(feproj1);
                fePlans.add(fep1);
                flattenLst.add(true);
            }

            POForEach fe = new POForEach(new OperatorKey(scope, nodeGen.getNextNodeId(scope)), cross.getRequestedParallelism(), fePlans, flattenLst );
            fe.addOriginalLocation(cross.getAlias(), cross.getLocation());
            currentPlan.add(fe);
            try{
                currentPlan.connect(poPackage, fe);
            }catch (PlanException e1) {
                int errCode = 2015;
                String msg = "Invalid physical operators in the physical plan" ;
                throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e1);
            }
            logToPhyMap.put(cross, fe);
        }
    }

    @Override
    public void visit(LOStream stream) throws FrontendException {
        String scope = DEFAULT_SCOPE;
        POStream poStream = new POStream(new OperatorKey(scope, nodeGen
                .getNextNodeId(scope)), stream.getExecutableManager(),
                stream.getStreamingCommand(), this.pc.getProperties());
        poStream.addOriginalLocation(stream.getAlias(), stream.getLocation());
        currentPlan.add(poStream);
        logToPhyMap.put(stream, poStream);

        List<Operator> op = stream.getPlan().getPredecessors(stream);

        PhysicalOperator from;
        if(op != null) {
            from = logToPhyMap.get(op.get(0));
        } else {
            int errCode = 2051;
            String msg = "Did not find a predecessor for Stream." ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG);
        }

        try {
            currentPlan.connect(from, poStream);
        } catch (PlanException e) {
            int errCode = 2015;
            String msg = "Invalid physical operators in the physical plan" ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
        }
    }

    @Override
    public void visit(LOInnerLoad load) throws FrontendException {
        String scope = DEFAULT_SCOPE;

        POProject exprOp = new POProject(new OperatorKey(scope, nodeGen
              .getNextNodeId(scope)));

        LogicalSchema s = load.getSchema();

        if (load.sourceIsBag()) {
            exprOp.setResultType(DataType.BAG);
            exprOp.setOverloaded(true);
        }
        else {
            if (s!=null)
                exprOp.setResultType(s.getField(0).type);
            else
                exprOp.setResultType(DataType.BYTEARRAY);
        }

        ProjectExpression proj = load.getProjection();
        if(proj.isProjectStar()){
            exprOp.setStar(proj.isProjectStar());
        }
        else if(proj.isRangeProject()){
            if(proj.getEndCol() != -1){
                //all other project-range should have been expanded by
                // project-star expander
                throw new AssertionError("project range that is not a " +
                "project-to-end seen in translation to physical plan!");
            }
            exprOp.setProjectToEnd(proj.getStartCol());
        }else {
            exprOp.setColumn(load.getColNum());
        }
        // set input to POProject to the predecessor of foreach

        logToPhyMap.put(load, exprOp);
        currentPlan.add(exprOp);
    }

    @Override
    public void visit(LOForEach foreach) throws FrontendException {
        String scope = DEFAULT_SCOPE;

        List<PhysicalPlan> innerPlans = new ArrayList<PhysicalPlan>();

        org.apache.pig.newplan.logical.relational.LogicalPlan inner = foreach.getInnerPlan();
        LOGenerate gen = (LOGenerate)inner.getSinks().get(0);

        List<LogicalExpressionPlan> exps = gen.getOutputPlans();
        List<Operator> preds = inner.getPredecessors(gen);

        currentPlans.push(currentPlan);

        // we need to translate each predecessor of LOGenerate into a physical plan.
        // The physical plan should contain the expression plan for this predecessor plus
        // the subtree starting with this predecessor
        for (int i=0; i<exps.size(); i++) {
            currentPlan = new PhysicalPlan();
            // translate the expression plan
            PlanWalker childWalker = new ReverseDependencyOrderWalkerWOSeenChk(exps.get(i));
            pushWalker(childWalker);
            childWalker.walk(new ExpToPhyTranslationVisitor(exps.get(i),
                    childWalker, gen, currentPlan, logToPhyMap));
            popWalker();

            List<Operator> leaves = exps.get(i).getSinks();
            for(Operator l: leaves) {
                PhysicalOperator op = logToPhyMap.get(l);
                if (l instanceof ProjectExpression ) {
                    int input = ((ProjectExpression)l).getInputNum();

                    // for each sink projection, get its input logical plan and translate it
                    Operator pred = preds.get(input);
                    childWalker = new SubtreeDependencyOrderWalker(inner, pred);
                    pushWalker(childWalker);
                    childWalker.walk(this);
                    popWalker();

                    // get the physical operator of the leaf of input logical plan
                    PhysicalOperator leaf = logToPhyMap.get(pred);

                    if (pred instanceof LOInnerLoad) {
                        // if predecessor is only an LOInnerLoad, remove the project that
                        // comes from LOInnerLoad and change the column of project that
                        // comes from expression plan
                        currentPlan.remove(leaf);
                        logToPhyMap.remove(pred);

                        POProject leafProj = (POProject)leaf;
                        try {
                            if(leafProj.isStar()){
                                ((POProject)op).setStar(true);
                            }
                            else if(leafProj.isProjectToEnd()){
                                ((POProject)op).setProjectToEnd(leafProj.getStartCol());
                            }else {
                                ((POProject)op).setColumn(leafProj.getColumn() );
                            }

                        } catch (ExecException e) {
                            throw new FrontendException(foreach, "Cannot get column from "+leaf, 2230, e);
                        }

                    }else{
                        currentPlan.connect(leaf, op);
                    }
                }
            }
            innerPlans.add(currentPlan);
        }

        currentPlan = currentPlans.pop();

        // PhysicalOperator poGen = new POGenerate(new OperatorKey("",
        // r.nextLong()), inputs, toBeFlattened);
        boolean[] flatten = gen.getFlattenFlags();
        List<Boolean> flattenList = new ArrayList<Boolean>();
        for(boolean fl: flatten) {
            flattenList.add(fl);
        }
        LogicalSchema logSchema = foreach.getSchema();
        Schema schema = null;
        if (logSchema != null) {
            try {
                schema = Schema.getPigSchema(new ResourceSchema(logSchema));
            } catch (FrontendException e) {
                throw new RuntimeException("LogicalSchema in foreach unable to be converted to Schema: " + logSchema, e);
            }
        }
        if (schema != null) {
            SchemaTupleFrontend.registerToGenerateIfPossible(schema, false, GenContext.FOREACH); //TODO may need to be appendable
        }
        POForEach poFE = new POForEach(new OperatorKey(scope, nodeGen
                .getNextNodeId(scope)), foreach.getRequestedParallelism(), innerPlans, flattenList, schema);
        poFE.addOriginalLocation(foreach.getAlias(), foreach.getLocation());
        poFE.setResultType(DataType.BAG);
        logToPhyMap.put(foreach, poFE);
        currentPlan.add(poFE);

        // generate cannot have multiple inputs
        List<Operator> op = foreach.getPlan().getPredecessors(foreach);

        // generate may not have any predecessors
        if (op == null)
            return;

        PhysicalOperator from = logToPhyMap.get(op.get(0));
        try {
           currentPlan.connect(from, poFE);
        } catch (Exception e) {
            int errCode = 2015;
            String msg = "Invalid physical operators in the physical plan" ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
        }

        translateSoftLinks(foreach);
    }

    /**
     * This function takes in a List of LogicalExpressionPlan and converts them to
     * a list of PhysicalPlans
     *
     * @param plans
     * @return
     * @throws FrontendException
     */
    private List<PhysicalPlan> translateExpressionPlans(LogicalRelationalOperator loj,
            List<LogicalExpressionPlan> plans ) throws FrontendException {
        List<PhysicalPlan> exprPlans = new ArrayList<PhysicalPlan>();
        if( plans == null || plans.size() == 0 ) {
            return exprPlans;
        }

        // Save the current plan onto stack
        currentPlans.push(currentPlan);

        for( LogicalExpressionPlan lp : plans ) {
            currentPlan = new PhysicalPlan();

            // We spawn a new Dependency Walker and use it
            // PlanWalker childWalker = currentWalker.spawnChildWalker(lp);
            PlanWalker childWalker = new ReverseDependencyOrderWalkerWOSeenChk(lp);

            // Save the old walker and use childWalker as current Walker
            pushWalker(childWalker);

            // We create a new ExpToPhyTranslationVisitor to walk the ExpressionPlan
            currentWalker.walk(
                    new ExpToPhyTranslationVisitor(
                            currentWalker.getPlan(),
                            childWalker, loj, currentPlan, logToPhyMap) );

            exprPlans.add(currentPlan);
            popWalker();
        }

        // Pop the current plan back out
        currentPlan = currentPlans.pop();

        return exprPlans;
    }

    @Override
    public void visit(LOStore loStore) throws FrontendException {
        String scope = DEFAULT_SCOPE;
        //        System.err.println("Entering Store");
        POStore store = new POStore(new OperatorKey(scope, nodeGen
                .getNextNodeId(scope)));
        store.addOriginalLocation(loStore.getAlias(), loStore.getLocation());
        store.setSFile(loStore.getOutputSpec());
        store.setInputSpec(loStore.getInputSpec());
        store.setSignature(loStore.getSignature());
        store.setSortInfo(loStore.getSortInfo());
        store.setIsTmpStore(loStore.isTmpStore());
        store.setStoreFunc(loStore.getStoreFunc());
        store.setSchema(Util.translateSchema( loStore.getSchema() ));
        if (loStore.getStoreFunc() instanceof StoreResources) {
            store.setCacheFiles(((StoreResources)loStore.getStoreFunc()).getCacheFiles());
            store.setShipFiles(((StoreResources)loStore.getStoreFunc()).getShipFiles());
        }

        currentPlan.add(store);

        List<Operator> op = loStore.getPlan().getPredecessors(loStore);
        PhysicalOperator from = null;

        if(op != null) {
            from = logToPhyMap.get(op.get(0));
//             TODO Implement sorting when we have a LOSort (new) and LOLimit (new) operator ready
//            SortInfo sortInfo = null;
//            // if store's predecessor is limit,
//            // check limit's predecessor
//            if(op.get(0) instanceof LOLimit) {
//                op = loStore.getPlan().getPredecessors(op.get(0));
//            }
//            PhysicalOperator sortPhyOp = logToPhyMap.get(op.get(0));
//            // if this predecessor is a sort, get
//            // the sort info.
//            if(op.get(0) instanceof LOSort) {
//                sortInfo = ((POSort)sortPhyOp).getSortInfo();
//            }
//            store.setSortInfo(sortInfo);
//        } else {
//            int errCode = 2051;
//            String msg = "Did not find a predecessor for Store." ;
//            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG);
        }

        try {
            currentPlan.connect(from, store);
        } catch (PlanException e) {
            int errCode = 2015;
            String msg = "Invalid physical operators in the physical plan" ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
        }
        logToPhyMap.put(loStore, store);
        //        System.err.println("Exiting Store");
    }

    @Override
    public void visit( LOCogroup cg ) throws FrontendException {
        switch (cg.getGroupType()) {
        case COLLECTED:
            translateCollectedCogroup(cg);
            break;
        case REGULAR:
            POPackage poPackage = compileToLR_GR_PackTrio(cg, cg.getCustomPartitioner(), cg.getInner(), cg.getExpressionPlans());
            poPackage.getPkgr().setPackageType(PackageType.GROUP);
            logToPhyMap.put(cg, poPackage);
            break;
        case MERGE:
            translateMergeCogroup(cg);
            break;
        default:
            throw new LogicalToPhysicalTranslatorException("Unknown CoGroup Modifier",PigException.BUG);
        }
        translateSoftLinks(cg);
    }

    private void translateCollectedCogroup(LOCogroup cg) throws FrontendException {
        // can have only one input
        LogicalRelationalOperator pred = (LogicalRelationalOperator) plan.getPredecessors(cg).get(0);
        List<LogicalExpressionPlan> exprPlans =  cg.getExpressionPlans().get(0);
        POCollectedGroup physOp = new POCollectedGroup(new OperatorKey(
                DEFAULT_SCOPE, nodeGen.getNextNodeId(DEFAULT_SCOPE)));
        physOp.addOriginalLocation(cg.getAlias(), cg.getLocation());
        List<PhysicalPlan> pExprPlans = translateExpressionPlans(cg, exprPlans);

        try {
            physOp.setPlans(pExprPlans);
        } catch (PlanException pe) {
            int errCode = 2071;
            String msg = "Problem with setting up map group's plans.";
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, pe);
        }
        Byte type = null;
        if (exprPlans.size() > 1) {
            type = DataType.TUPLE;
            physOp.setKeyType(type);
        } else {
            type = pExprPlans.get(0).getLeaves().get(0).getResultType();
            physOp.setKeyType(type);
        }
        physOp.setResultType(DataType.TUPLE);

        currentPlan.add(physOp);

        try {
            currentPlan.connect(logToPhyMap.get(pred), physOp);
        } catch (PlanException e) {
            int errCode = 2015;
            String msg = "Invalid physical operators in the physical plan" ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
        }

        logToPhyMap.put(cg, physOp);
    }

    private POMergeCogroup compileToMergeCogrp(LogicalRelationalOperator relationalOp,
            MultiMap<Integer, LogicalExpressionPlan> innerPlans) throws FrontendException {

        List<Operator> inputs = relationalOp.getPlan().getPredecessors(relationalOp);
        // LocalRearrange corresponding to each of input
        // LR is needed to extract keys out of the tuples.

        POLocalRearrange[] innerLRs = new POLocalRearrange[inputs.size()];
        int count = 0;
        List<PhysicalOperator> inpPOs = new ArrayList<PhysicalOperator>(inputs.size());

        for (int i=0;i<inputs.size();i++) {
            Operator op = inputs.get(i);
            PhysicalOperator physOp = logToPhyMap.get(op);
            inpPOs.add(physOp);

            List<LogicalExpressionPlan> plans = innerPlans.get(i);
            POLocalRearrange poInnerLR = new POLocalRearrange(new OperatorKey(DEFAULT_SCOPE, nodeGen.getNextNodeId(DEFAULT_SCOPE)));
            poInnerLR.addOriginalLocation(relationalOp.getAlias(), relationalOp.getLocation());
            // LR will contain list of physical plans, because there could be
            // multiple keys and each key can be an expression.
            List<PhysicalPlan> exprPlans = translateExpressionPlans(relationalOp, plans);
            try {
                poInnerLR.setPlans(exprPlans);
            } catch (PlanException pe) {
                int errCode = 2071;
                String msg = "Problem with setting up local rearrange's plans.";
                throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, pe);
            }
            innerLRs[count] = poInnerLR;
            try {
                poInnerLR.setIndex(count++);
            } catch (ExecException e1) {
                int errCode = 2058;
                String msg = "Unable to set index on newly create POLocalRearrange.";
                throw new VisitorException(msg, errCode, PigException.BUG, e1);
            }
            poInnerLR.setKeyType(plans.size() > 1 ? DataType.TUPLE :
                        exprPlans.get(0).getLeaves().get(0).getResultType());
            poInnerLR.setResultType(DataType.TUPLE);
        }

        POMergeCogroup poCogrp = new POMergeCogroup(new OperatorKey(
                DEFAULT_SCOPE, nodeGen.getNextNodeId(DEFAULT_SCOPE)),inpPOs,innerLRs,relationalOp.getRequestedParallelism());
        return poCogrp;
    }

    private void translateMergeCogroup(LOCogroup cg) throws FrontendException {
        if(!validateMergeCogrp(cg.getInner())){
            throw new LogicalToPhysicalTranslatorException("Inner is not " +
                    "supported for any relation on Merge Cogroup.");
        }
        List<Operator> inputs = cg.getPlan().getPredecessors(cg);
        MapSideMergeValidator validator = new MapSideMergeValidator();
        validator.validateMapSideMerge(inputs, cg.getPlan());
        POMergeCogroup poCogrp = compileToMergeCogrp(cg, cg.getExpressionPlans());
        poCogrp.setResultType(DataType.TUPLE);
        poCogrp.addOriginalLocation(cg.getAlias(), cg.getLocation());
        currentPlan.add(poCogrp);
        for (Operator op : inputs) {
            try {
                currentPlan.connect(logToPhyMap.get(op), poCogrp);
            } catch (PlanException e) {
                int errCode = 2015;
                String msg = "Invalid physical operators in the physical plan" ;
                throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
            }
        }
        logToPhyMap.put(cg, poCogrp);
    }

    private boolean validateMergeCogrp(boolean[] innerFlags){

        for(boolean flag : innerFlags){
            if(flag)
                return false;
        }
        return true;
    }

    @Override
    public void visit(LOJoin loj) throws FrontendException {

        String scope = DEFAULT_SCOPE;

        // List of join predicates
        List<Operator> inputs = loj.getPlan().getPredecessors(loj);

        // mapping of inner join physical plans corresponding to inner physical operators.
        MultiMap<PhysicalOperator, PhysicalPlan> joinPlans = new LinkedMultiMap<PhysicalOperator, PhysicalPlan>();

        // Outer list corresponds to join predicates. Inner list is inner physical plan of each predicate.
        List<List<PhysicalPlan>> ppLists = new ArrayList<List<PhysicalPlan>>();

        // List of physical operator corresponding to join predicates.
        List<PhysicalOperator> inp = new ArrayList<PhysicalOperator>();

        // Outer list corresponds to join predicates and inner list corresponds to type of keys for each predicate.
        List<List<Byte>> keyTypes = new ArrayList<List<Byte>>();

        boolean[] innerFlags = loj.getInnerFlags();
        String alias = loj.getAlias();
        SourceLocation location = loj.getLocation();
        int parallel = loj.getRequestedParallelism();

        for (int i=0;i<inputs.size();i++) {
            Operator op = inputs.get(i);
            PhysicalOperator physOp = logToPhyMap.get(op);
            inp.add(physOp);
            List<LogicalExpressionPlan> plans =  (List<LogicalExpressionPlan>)loj.getJoinPlan(i);

            List<PhysicalPlan> exprPlans = translateExpressionPlans(loj, plans);

            ppLists.add(exprPlans);
            joinPlans.put(physOp, exprPlans);

            // Key could potentially be a tuple. So, we visit all exprPlans to get types of members of tuples.
            List<Byte> tupleKeyMemberTypes = new ArrayList<Byte>();
            for(PhysicalPlan exprPlan : exprPlans)
                tupleKeyMemberTypes.add(exprPlan.getLeaves().get(0).getResultType());
            keyTypes.add(tupleKeyMemberTypes);
        }

        if (loj.getJoinType() == LOJoin.JOINTYPE.SKEWED) {
            POSkewedJoin skj;
            try {
                skj = new POSkewedJoin(new OperatorKey(scope,nodeGen.getNextNodeId(scope)),
                                        parallel,inp, innerFlags);
                skj.addOriginalLocation(alias, location);
                skj.setJoinPlans(joinPlans);
            }
            catch (Exception e) {
                int errCode = 2015;
                String msg = "Skewed Join creation failed";
                throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
            }
            skj.setResultType(DataType.TUPLE);

            for (int i=0; i < inputs.size(); i++) {
                Operator op = inputs.get(i);
                if (!innerFlags[i]) {
                    try {
                        LogicalSchema s = ((LogicalRelationalOperator)op).getSchema();
                        // if the schema cannot be determined
                        if (s == null) {
                            throw new FrontendException(loj, "Cannot determine skewed join schema", 2247);
                        }
                        skj.addSchema(Util.translateSchema(s));
                    } catch (FrontendException e) {
                        int errCode = 2015;
                        String msg = "Couldn't set the schema for outer join" ;
                        throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
                    }
                } else {
                    // This will never be retrieved. It just guarantees that the index will be valid when
                    // MRCompiler is trying to read the schema
                    skj.addSchema(null);
                }
            }

            currentPlan.add(skj);

            for (Operator op : inputs) {
                try {
                    currentPlan.connect(logToPhyMap.get(op), skj);
                } catch (PlanException e) {
                    int errCode = 2015;
                    String msg = "Invalid physical operators in the physical plan" ;
                    throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
                }
            }
            logToPhyMap.put(loj, skj);
        }
        else if(loj.getJoinType() == LOJoin.JOINTYPE.REPLICATED) {
            Schema[] inputSchemas = new Schema[inputs.size()];
            Schema[] keySchemas = new Schema[inputs.size()];

            outer: for (int i = 0; i < inputs.size(); i++) {
                LogicalSchema logicalSchema = ((LogicalRelationalOperator)inputs.get(i)).getSchema();
                if (logicalSchema == null) {
                    continue;
                }
                Schema toGen = Schema.getPigSchema(new ResourceSchema(logicalSchema));
                // This registers the value piece
                SchemaTupleFrontend.registerToGenerateIfPossible(toGen, false, GenContext.FR_JOIN);
                inputSchemas[i] = toGen;

                Schema keyToGen = new Schema();
                for (Byte byt : keyTypes.get(i)) {
                    // We cannot generate any nested code because that information is thrown away
                    if (byt == null || DataType.isComplex(byt.byteValue())) {
                        continue outer;
                    }
                    keyToGen.add(new FieldSchema(null, byt));
                }

                SchemaTupleFrontend.registerToGenerateIfPossible(keyToGen, false, GenContext.FR_JOIN);
                keySchemas[i] = keyToGen;
            }

            int fragment = 0;
            POFRJoin pfrj;
            try {
                boolean isLeftOuter = false;
                // We dont check for bounds issue as we assume that a join
                // involves atleast two inputs
                isLeftOuter = !innerFlags[1];

                Tuple nullTuple = null;
                if( isLeftOuter ) {
                    try {
                        // We know that in a Left outer join its only a two way
                        // join, so we assume index of 1 for the right input
                        LogicalSchema inputSchema = ((LogicalRelationalOperator)inputs.get(1)).getSchema();

                        // We check if we have a schema before the join
                        if(inputSchema == null) {
                            int errCode = 1109;
                            String msg = "Input (" + ((LogicalRelationalOperator)inputs.get(1)).getAlias() + ") " +
                            "on which outer join is desired should have a valid schema";
                            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.INPUT);
                        }

                        // Using the schema we decide the number of columns/fields
                        // in the nullTuple
                        nullTuple = TupleFactory.getInstance().newTuple(inputSchema.size());
                        for(int j = 0; j < inputSchema.size(); j++) {
                            nullTuple.set(j, null);
                        }

                    } catch( FrontendException e ) {
                        int errCode = 2104;
                        String msg = "Error while determining the schema of input";
                        throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
                    }
                }

                pfrj = new POFRJoin(new OperatorKey(scope,nodeGen.getNextNodeId(scope)),
                                        parallel,
                                        inp,
                                        ppLists,
                                        keyTypes,
                                        null,
                                        fragment,
                                        isLeftOuter,
                                        nullTuple,
                                        inputSchemas,
                                        keySchemas);
                pfrj.addOriginalLocation(alias, location);
            } catch (ExecException e1) {
                int errCode = 2058;
                String msg = "Unable to set index on newly create POLocalRearrange.";
                throw new VisitorException(msg, errCode, PigException.BUG, e1);
            }
            pfrj.setResultType(DataType.TUPLE);
            currentPlan.add(pfrj);
            for (Operator op : inputs) {
                try {
                    currentPlan.connect(logToPhyMap.get(op), pfrj);
                } catch (PlanException e) {
                    int errCode = 2015;
                    String msg = "Invalid physical operators in the physical plan" ;
                    throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
                }
            }
            logToPhyMap.put(loj, pfrj);
        } else if ( (loj.getJoinType() == LOJoin.JOINTYPE.MERGE || loj.getJoinType() == LOJoin.JOINTYPE.MERGESPARSE)
                && (new MapSideMergeValidator().validateMapSideMerge(inputs,loj.getPlan()))) {

            PhysicalOperator smj;
            boolean usePOMergeJoin = inputs.size() == 2 && innerFlags[0] && innerFlags[1] ;

            if(usePOMergeJoin){
                // We register the merge join schema information for code generation
                LogicalSchema logicalSchema = ((LogicalRelationalOperator)inputs.get(0)).getSchema();
                Schema leftSchema = null;
                if (logicalSchema != null) {
                    leftSchema = Schema.getPigSchema(new ResourceSchema(logicalSchema));
                }
                logicalSchema = ((LogicalRelationalOperator)inputs.get(1)).getSchema();
                Schema rightSchema = null;
                if (logicalSchema != null) {
                    rightSchema = Schema.getPigSchema(new ResourceSchema(logicalSchema));
                }
                logicalSchema = loj.getSchema();
                Schema mergedSchema = null;
                if (logicalSchema != null) {
                    mergedSchema = Schema.getPigSchema(new ResourceSchema(logicalSchema));
                }

                if (leftSchema != null) {
                    SchemaTupleFrontend.registerToGenerateIfPossible(leftSchema, false, GenContext.MERGE_JOIN);
                }
                if (rightSchema != null) {
                    SchemaTupleFrontend.registerToGenerateIfPossible(rightSchema, false, GenContext.MERGE_JOIN);
                }
                if (mergedSchema != null) {
                    SchemaTupleFrontend.registerToGenerateIfPossible(mergedSchema, false, GenContext.MERGE_JOIN);
                }

                // inner join on two sorted inputs. We have less restrictive
                // implementation here in a form of POMergeJoin which doesn't
                // require loaders to implement collectable interface.
                try {
                    smj = new POMergeJoin(new OperatorKey(scope,nodeGen.getNextNodeId(scope)),
                                            parallel,
                                            inp,
                                            joinPlans,
                                            keyTypes,
                                            loj.getJoinType(),
                                            leftSchema,
                                            rightSchema,
                                            mergedSchema);
                }
                catch (PlanException e) {
                    int errCode = 2042;
                    String msg = "Merge Join creation failed";
                    throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
                }
                logToPhyMap.put(loj, smj);
            } else {
                // in all other cases we fall back to POMergeCogroup + Flattening FEs
                smj = compileToMergeCogrp(loj, loj.getExpressionPlans());
            }

            smj.setResultType(DataType.TUPLE);
            currentPlan.add(smj);
            smj.addOriginalLocation(alias, location);
            for (Operator op : inputs) {
                try {
                    currentPlan.connect(logToPhyMap.get(op), smj);
                } catch (PlanException e) {
                    int errCode = 2015;
                    String msg = "Invalid physical operators in the physical plan" ;
                    throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
                }
            }

            if(!usePOMergeJoin){
                // Now create and configure foreach which will flatten the output
                // of cogroup.
                POForEach fe = compileFE4Flattening(innerFlags,  scope, parallel, alias, location, inputs);
                currentPlan.add(fe);
                try {
                    currentPlan.connect(smj, fe);
                } catch (PlanException e) {
                    throw new LogicalToPhysicalTranslatorException(e.getMessage(),e.getErrorCode(),e.getErrorSource(),e);
                }
                logToPhyMap.put(loj, fe);
            }

            return;
        }
        else if (loj.getJoinType() == LOJoin.JOINTYPE.HASH){
            POPackage poPackage = compileToLR_GR_PackTrio(loj, loj.getCustomPartitioner(), innerFlags, loj.getExpressionPlans());
            POForEach fe = compileFE4Flattening(innerFlags,  scope, parallel, alias, location, inputs);
            currentPlan.add(fe);
            try {
                currentPlan.connect(poPackage, fe);
            } catch (PlanException e) {
                throw new LogicalToPhysicalTranslatorException(e.getDetailedMessage(),
                        e.getErrorCode(),e.getErrorSource(),e);
            }
            logToPhyMap.put(loj, fe);
            poPackage.getPkgr().setPackageType(PackageType.JOIN);
        }
        translateSoftLinks(loj);
    }

    private POPackage compileToLR_GR_PackTrio(LogicalRelationalOperator relationalOp, String customPartitioner,
            boolean[] innerFlags, MultiMap<Integer, LogicalExpressionPlan> innerPlans) throws FrontendException {

        POGlobalRearrange poGlobal = new POGlobalRearrange(new OperatorKey(
                DEFAULT_SCOPE, nodeGen.getNextNodeId(DEFAULT_SCOPE)), relationalOp.getRequestedParallelism());
        poGlobal.addOriginalLocation(relationalOp.getAlias(), relationalOp.getLocation());
        poGlobal.setCustomPartitioner(customPartitioner);
        POPackage poPackage = new POPackage(new OperatorKey(DEFAULT_SCOPE, nodeGen
                .getNextNodeId(DEFAULT_SCOPE)), relationalOp.getRequestedParallelism());
        poPackage.addOriginalLocation(relationalOp.getAlias(), relationalOp.getLocation());
        currentPlan.add(poGlobal);
        currentPlan.add(poPackage);

        try {
            currentPlan.connect(poGlobal, poPackage);
        } catch (PlanException e1) {
            int errCode = 2015;
            String msg = "Invalid physical operators in the physical plan" ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e1);
        }

        int count = 0;
        Byte type = null;
        List<Operator> inputs = relationalOp.getPlan().getPredecessors(relationalOp);
        for (int i=0;i<inputs.size();i++) {
            Operator op = inputs.get(i);
            List<LogicalExpressionPlan> plans = innerPlans.get(i);
            POLocalRearrange physOp = new POLocalRearrange(new OperatorKey(
                    DEFAULT_SCOPE, nodeGen.getNextNodeId(DEFAULT_SCOPE)), relationalOp.getRequestedParallelism());
            physOp.addOriginalLocation(relationalOp.getAlias(), relationalOp.getLocation());
            List<PhysicalPlan> exprPlans = translateExpressionPlans(relationalOp, plans);
            try {
                physOp.setPlans(exprPlans);
            } catch (PlanException pe) {
                int errCode = 2071;
                String msg = "Problem with setting up local rearrange's plans.";
                throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, pe);
            }
            try {
                physOp.setIndex(count++);
            } catch (ExecException e1) {
                int errCode = 2058;
                String msg = "Unable to set index on newly create POLocalRearrange.";
                throw new VisitorException(msg, errCode, PigException.BUG, e1);
            }
            if (plans.size() > 1) {
                type = DataType.TUPLE;
                physOp.setKeyType(type);
            } else {
                type = exprPlans.get(0).getLeaves().get(0).getResultType();
                physOp.setKeyType(type);
            }
            physOp.setResultType(DataType.TUPLE);

            currentPlan.add(physOp);

            try {
                currentPlan.connect(logToPhyMap.get(op), physOp);
                currentPlan.connect(physOp, poGlobal);
            } catch (PlanException e) {
                int errCode = 2015;
                String msg = "Invalid physical operators in the physical plan" ;
                throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
            }
        }

        poPackage.getPkgr().setKeyType(type);
        poPackage.setResultType(DataType.TUPLE);
        poPackage.setNumInps(count);
        poPackage.getPkgr().setInner(innerFlags);
        return poPackage;
    }

    private POForEach compileFE4Flattening(boolean[] innerFlags,String scope,
            int parallel, String alias, SourceLocation location, List<Operator> inputs)
                throws FrontendException {

        List<PhysicalPlan> fePlans = new ArrayList<PhysicalPlan>();
        List<Boolean> flattenLst = new ArrayList<Boolean>();
        POForEach fe;
        try{
            for(int i=0;i< inputs.size();i++){
                PhysicalPlan fep1 = new PhysicalPlan();
                POProject feproj1 = new POProject(new OperatorKey(scope, nodeGen.getNextNodeId(scope)),
                        parallel, i+1); //i+1 since the first column is the "group" field
                feproj1.addOriginalLocation(alias, location);
                feproj1.setResultType(DataType.BAG);
                feproj1.setOverloaded(false);
                fep1.add(feproj1);
                fePlans.add(fep1);
                // the parser would have marked the side
                // where we need to keep empty bags on
                // non matched as outer (innerFlags[i] would be
                // false)
                if(!(innerFlags[i])) {
                    Operator joinInput = inputs.get(i);
                    // for outer join add a bincond
                    // which will project nulls when bag is
                    // empty
                    updateWithEmptyBagCheck(fep1, joinInput);
                }
                flattenLst.add(true);
            }

            fe = new POForEach(new OperatorKey(scope, nodeGen.getNextNodeId(scope)),
                    parallel, fePlans, flattenLst );
            fe.addOriginalLocation(alias, location);

        }catch (PlanException e1) {
            int errCode = 2015;
            String msg = "Invalid physical operators in the physical plan" ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e1);
        }
        return fe;
    }

    @Override
    public void visit(LOUnion loUnion) throws FrontendException {
        String scope = DEFAULT_SCOPE;
        POUnion physOp = new POUnion(new OperatorKey(scope,nodeGen.getNextNodeId(scope)), loUnion.getRequestedParallelism());
        physOp.addOriginalLocation(loUnion.getAlias(), loUnion.getLocation());
        currentPlan.add(physOp);
        physOp.setResultType(DataType.BAG);
        logToPhyMap.put(loUnion, physOp);
        List<Operator> ops = loUnion.getPlan().getPredecessors(loUnion);

        for (Operator l : ops) {
            PhysicalOperator from = logToPhyMap.get(l);
            try {
                currentPlan.connect(from, physOp);
            } catch (PlanException e) {
                int errCode = 2015;
                String msg = "Invalid physical operators in the physical plan" ;
                throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
            }
        }
    }

    @Override
    public void visit(LODistinct loDistinct) throws FrontendException {
        String scope = DEFAULT_SCOPE;
        PODistinct physOp = new PODistinct(new OperatorKey(scope,nodeGen.getNextNodeId(scope)), loDistinct.getRequestedParallelism());
        physOp.setCustomPartitioner(loDistinct.getCustomPartitioner());
        physOp.addOriginalLocation(loDistinct.getAlias(), loDistinct.getLocation());
        currentPlan.add(physOp);
        physOp.setResultType(DataType.BAG);
        logToPhyMap.put(loDistinct, physOp);
        Operator op = loDistinct.getPlan().getPredecessors(loDistinct).get(0);

        PhysicalOperator from = logToPhyMap.get(op);
        try {
            currentPlan.connect(from, physOp);
        } catch (PlanException e) {
            int errCode = 2015;
            String msg = "Invalid physical operators in the physical plan" ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
        }
    }

    @Override
    public void visit(LOLimit loLimit) throws FrontendException {
        String scope = DEFAULT_SCOPE;
        POLimit poLimit = new POLimit(new OperatorKey(scope, nodeGen.getNextNodeId(scope)),
                loLimit.getRequestedParallelism());
        poLimit.setLimit(loLimit.getLimit());
        poLimit.addOriginalLocation(loLimit.getAlias(), loLimit.getLocation());
        poLimit.setResultType(DataType.BAG);
        currentPlan.add(poLimit);
        logToPhyMap.put(loLimit, poLimit);

        if (loLimit.getLimitPlan() != null) {
            // add expression plan to POLimit
            currentPlans.push(currentPlan);
            currentPlan = new PhysicalPlan();
            PlanWalker childWalker = new ReverseDependencyOrderWalkerWOSeenChk(loLimit.getLimitPlan());
            pushWalker(childWalker);
            currentWalker.walk(new ExpToPhyTranslationVisitor(currentWalker.getPlan(), childWalker, loLimit,
                    currentPlan, logToPhyMap));
            poLimit.setLimitPlan(currentPlan);
            popWalker();
            currentPlan = currentPlans.pop();
        }

        Operator op = loLimit.getPlan().getPredecessors(loLimit).get(0);

        PhysicalOperator from = logToPhyMap.get(op);
        try {
            currentPlan.connect(from, poLimit);
        } catch (PlanException e) {
            int errCode = 2015;
            String msg = "Invalid physical operators in the physical plan" ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
        }

        translateSoftLinks(loLimit);
    }

    @Override
    public void visit(LOSplit loSplit) throws FrontendException {
        String scope = DEFAULT_SCOPE;
        POSplit physOp = new POSplit(new OperatorKey(scope, nodeGen
                .getNextNodeId(scope)), loSplit.getRequestedParallelism());
        physOp.addOriginalLocation(loSplit.getAlias(), loSplit.getLocation());
        FileSpec splStrFile;
        try {
            splStrFile = new FileSpec(FileLocalizer.getTemporaryPath(pc).toString(),new FuncSpec(Utils.getTmpFileCompressorName(pc)));
        } catch (IOException e1) {
            byte errSrc = pc.getErrorSource();
            int errCode = 0;
            switch(errSrc) {
            case PigException.BUG:
                errCode = 2016;
                break;
            case PigException.REMOTE_ENVIRONMENT:
                errCode = 6002;
                break;
            case PigException.USER_ENVIRONMENT:
                errCode = 4003;
                break;
            }
            String msg = "Unable to obtain a temporary path." ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, errSrc, e1);

        }
        physOp.setSplitStore(splStrFile);
        logToPhyMap.put(loSplit, physOp);

        currentPlan.add(physOp);

        List<Operator> op = loSplit.getPlan().getPredecessors(loSplit);
        PhysicalOperator from;

        if(op != null) {
            from = logToPhyMap.get(op.get(0));
        } else {
            int errCode = 2051;
            String msg = "Did not find a predecessor for Split." ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG);
        }

        try {
            currentPlan.connect(from, physOp);
        } catch (PlanException e) {
            int errCode = 2015;
            String msg = "Invalid physical operators in the physical plan" ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
        }
    }

    @Override
    public void visit(LOSplitOutput loSplitOutput) throws FrontendException {
        String scope = DEFAULT_SCOPE;
        //        System.err.println("Entering Filter");
        POFilter poFilter = new POFilter(new OperatorKey(scope, nodeGen
                .getNextNodeId(scope)), loSplitOutput.getRequestedParallelism());
        poFilter.addOriginalLocation(loSplitOutput.getAlias(), loSplitOutput.getLocation());
        poFilter.setResultType(DataType.BAG);
        currentPlan.add(poFilter);
        logToPhyMap.put(loSplitOutput, poFilter);
        currentPlans.push(currentPlan);

        currentPlan = new PhysicalPlan();

//        PlanWalker childWalker = currentWalker
//                .spawnChildWalker(filter.getFilterPlan());
        PlanWalker childWalker = new ReverseDependencyOrderWalkerWOSeenChk(loSplitOutput.getFilterPlan());
        pushWalker(childWalker);
        //currentWalker.walk(this);
        currentWalker.walk(
                new ExpToPhyTranslationVisitor( currentWalker.getPlan(),
                        childWalker, loSplitOutput, currentPlan, logToPhyMap) );
        popWalker();

        poFilter.setPlan(currentPlan);
        currentPlan = currentPlans.pop();

        List<Operator> op = loSplitOutput.getPlan().getPredecessors(loSplitOutput);

        PhysicalOperator from;
        if(op != null) {
            from = logToPhyMap.get(op.get(0));
        } else {
            int errCode = 2051;
            String msg = "Did not find a predecessor for Filter." ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG);
        }

        try {
            currentPlan.connect(from, poFilter);
        } catch (PlanException e) {
            int errCode = 2015;
            String msg = "Invalid physical operators in the physical plan" ;
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
        }

        translateSoftLinks(loSplitOutput);
        //        System.err.println("Exiting Filter");
    }
    /**
     * updates plan with check for empty bag and if bag is empty to flatten a bag
     * with as many null's as dictated by the schema
     * @param fePlan the plan to update
     * @param joinInput the relation for which the corresponding bag is being checked
     * @throws FrontendException
     */
    public static void updateWithEmptyBagCheck(PhysicalPlan fePlan, Operator joinInput) throws FrontendException {
        LogicalSchema inputSchema = null;
        try {
            inputSchema = ((LogicalRelationalOperator) joinInput).getSchema();

            if(inputSchema == null) {
                int errCode = 1109;
                String msg = "Input (" + ((LogicalRelationalOperator) joinInput).getAlias() + ") " +
                        "on which outer join is desired should have a valid schema";
                throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.INPUT);
            }
        } catch (FrontendException e) {
            int errCode = 2104;
            String msg = "Error while determining the schema of input";
            throw new LogicalToPhysicalTranslatorException(msg, errCode, PigException.BUG, e);
        }

        CompilerUtils.addEmptyBagOuterJoin(fePlan, Util.translateSchema(inputSchema));

    }

    private void translateSoftLinks(Operator op) throws FrontendException {
        List<Operator> preds = op.getPlan().getSoftLinkPredecessors(op);

        if (preds == null)
            return;

        for (Operator pred : preds) {
            PhysicalOperator from = logToPhyMap.get(pred);
            currentPlan.createSoftLink(from, logToPhyMap.get(op));
        }
    }
}
