/*
* 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;
}
}