/*
* 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.impl.util;
import java.util.ArrayList;
import java.util.List;
import org.apache.pig.EvalFunc;
import org.apache.pig.FuncSpec;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.ConstantExpression;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POBinCond;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POProject;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.plans.PhysicalPlan;
import org.apache.pig.builtin.IsEmpty;
import org.apache.pig.data.DataBag;
import org.apache.pig.data.DataType;
import org.apache.pig.data.NonSpillableDataBag;
import org.apache.pig.data.Tuple;
import org.apache.pig.data.TupleFactory;
import org.apache.pig.impl.PigContext;
import org.apache.pig.impl.logicalLayer.schema.Schema;
import org.apache.pig.impl.plan.NodeIdGenerator;
import org.apache.pig.impl.plan.OperatorKey;
import org.apache.pig.impl.plan.PlanException;
/*
* A class to add util functions that gets used by LogToPhyTranslator and MRCompiler
*
*/
public class CompilerUtils {
public static void addEmptyBagOuterJoin(PhysicalPlan fePlan, Schema inputSchema) throws PlanException {
// we currently have POProject[bag] as the only operator in the plan
// If the bag is an empty bag, we should replace
// it with a bag with one tuple with null fields so that when we flatten
// we do not drop records (flatten will drop records if the bag is left
// as an empty bag) and actually project nulls for the fields in
// the empty bag
// So we need to get to the following state:
// POProject[Bag]
// \
// POUserFunc["IsEmpty()"] Const[Bag](bag with null fields)
// \ | POProject[Bag]
// \ | /
// POBinCond
POProject relationProject = (POProject) fePlan.getRoots().get(0);
try {
// condition of the bincond
POProject relationProjectForIsEmpty = relationProject.clone();
fePlan.add(relationProjectForIsEmpty);
String scope = relationProject.getOperatorKey().scope;
FuncSpec isEmptySpec = new FuncSpec(IsEmpty.class.getName());
Object f = PigContext.instantiateFuncFromSpec(isEmptySpec);
POUserFunc isEmpty = new POUserFunc(new OperatorKey(scope, NodeIdGenerator.getGenerator().
getNextNodeId(scope)), -1, null, isEmptySpec, (EvalFunc) f);
isEmpty.setResultType(DataType.BOOLEAN);
fePlan.add(isEmpty);
fePlan.connect(relationProjectForIsEmpty, isEmpty);
// lhs of bincond (const bag with null fields)
ConstantExpression ce = new ConstantExpression(new OperatorKey(scope,
NodeIdGenerator.getGenerator().getNextNodeId(scope)));
// the following should give a tuple with the
// required number of nulls
Tuple t = TupleFactory.getInstance().newTuple(inputSchema.size());
for(int i = 0; i < inputSchema.size(); i++) {
t.set(i, null);
}
List<Tuple> bagContents = new ArrayList<Tuple>(1);
bagContents.add(t);
DataBag bg = new NonSpillableDataBag(bagContents);
ce.setValue(bg);
ce.setResultType(DataType.BAG);
//this operator doesn't have any predecessors
fePlan.add(ce);
//rhs of bincond is the original project
// let's set up the bincond now
POBinCond bincond = new POBinCond(new OperatorKey(scope,
NodeIdGenerator.getGenerator().getNextNodeId(scope)));
bincond.setCond(isEmpty);
bincond.setLhs(ce);
bincond.setRhs(relationProject);
bincond.setResultType(DataType.BAG);
fePlan.add(bincond);
fePlan.connect(isEmpty, bincond);
fePlan.connect(ce, bincond);
fePlan.connect(relationProject, bincond);
} catch (Exception e) {
throw new PlanException("Error setting up outerjoin", e);
}
}
}