| /* |
| * 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.builtin; |
| |
| import java.io.IOException; |
| import java.util.HashMap; |
| import java.util.Map; |
| |
| import org.apache.pig.EvalFunc; |
| import org.apache.pig.backend.executionengine.ExecException; |
| import org.apache.pig.data.BagFactory; |
| 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.logicalLayer.FrontendException; |
| import org.apache.pig.impl.logicalLayer.schema.Schema; |
| |
| /** |
| * This UDF accepts a Map as input with values of any primitive data type. <br /> |
| * UDF swaps keys with values and returns the new inverse Map. <br /> |
| * Note in case original values are non-unique, the resulting Map would <br /> |
| * contain String Key -> DataBag of values. Here the bag of values is composed <br /> |
| * of the original keys having the same value. <br /> |
| * |
| * <pre> |
| * Note: 1. UDF accepts Map with Values of primitive data type |
| * 2. UDF returns Map<String,DataBag> |
| * <code> |
| * grunt> cat 1data |
| * [open#1,1#2,11#2] |
| * [apache#2,3#4,12#24] |
| * |
| * <br /> |
| * grunt> a = load 'data' as (M:[int]); |
| * grunt> b = foreach a generate INVERSEMAP($0); |
| * |
| * grunt> dump b; |
| * ([2#{(1),(11)},apache#{(open)}]) |
| * ([hadoop#{(apache),(12)},4#{(3)}]) |
| * </code> |
| * </pre> |
| */ |
| @SuppressWarnings("unchecked") |
| public class INVERSEMAP extends EvalFunc<Map> { |
| private static final TupleFactory TUPLE_FACTORY = TupleFactory.getInstance(); |
| private static final BagFactory BAG_FACTORY = BagFactory.getInstance(); |
| |
| @Override |
| public Map exec(Tuple input) throws IOException { |
| if (input == null || input.size() == 0) |
| return null; |
| Map<String, Object> inputMap = (Map<String, Object>)input.get(0); |
| if(inputMap == null) { |
| return null; |
| } |
| |
| return doInverse(inputMap); |
| } |
| |
| @Override |
| public Schema outputSchema(Schema input) { |
| try{ |
| if(input.getField(0).type != DataType.MAP) { |
| throw new RuntimeException("Expected map, received schema " +DataType.findTypeName(input.getField(0).type)); |
| } |
| } catch(FrontendException e) { |
| throw new RuntimeException(e); |
| } |
| return new Schema(new Schema.FieldSchema(null, DataType.MAP)); |
| } |
| |
| private HashMap<String, DataBag> doInverse(Map<String,Object> original) throws ExecException { |
| final HashMap<String, DataBag> inverseMap = new HashMap<String, DataBag>(original.size()); |
| |
| for (Map.Entry<String, Object> entry : original.entrySet()) { |
| Object o = entry.getValue(); |
| String newKey; |
| |
| // Call toString for all primitive types, else throw an Exception |
| if (!(o instanceof Tuple || o instanceof DataBag)) { |
| newKey = o.toString(); |
| } else { |
| throw new ExecException("Wrong type. Value is of type " + o.getClass()); |
| } |
| |
| // Create a new bag if "newKey" does not exist in Map |
| DataBag bag = inverseMap.get(newKey); |
| if (bag == null) { |
| bag = new NonSpillableDataBag(); |
| bag.add(TUPLE_FACTORY.newTuple(entry.getKey())); |
| inverseMap.put(newKey, bag); |
| } else { |
| bag.add(TUPLE_FACTORY.newTuple(entry.getKey())); |
| } |
| } |
| return inverseMap; |
| } |
| |
| @Override |
| public boolean allowCompileTimeCalculation() { |
| return true; |
| } |
| } |