/*
* 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 hivemall.tools.map;
import java.util.Arrays;
import java.util.Map;
import java.util.TreeMap;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.exec.UDFArgumentLengthException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.udf.UDFType;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDF;
import org.apache.hadoop.hive.serde2.objectinspector.MapObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorUtils;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.IntObjectInspector;
@Description(name = "map_tail_n", value = "_FUNC_(map SRC, int N) - Returns the last N elements "
+ "from a sorted array of SRC")
@UDFType(deterministic = true, stateful = false)
public class MapTailNUDF extends GenericUDF {
private MapObjectInspector mapObjectInspector;
private IntObjectInspector intObjectInspector;
@Override
public ObjectInspector initialize(ObjectInspector[] arguments) throws UDFArgumentException {
if (arguments.length != 2) {
throw new UDFArgumentLengthException(
"map_tail_n only takes 2 arguments: map<object, object>, int");
}
if (!(arguments[0] instanceof MapObjectInspector)) {
throw new UDFArgumentException("The first argument must be a map");
}
this.mapObjectInspector = (MapObjectInspector) arguments[0];
if (!(arguments[1] instanceof IntObjectInspector)) {
throw new UDFArgumentException("The second argument must be an int");
}
this.intObjectInspector = (IntObjectInspector) arguments[1];
ObjectInspector keyOI = ObjectInspectorUtils.getStandardObjectInspector(mapObjectInspector.getMapKeyObjectInspector());
ObjectInspector valueOI = mapObjectInspector.getMapValueObjectInspector();
return ObjectInspectorFactory.getStandardMapObjectInspector(keyOI, valueOI);
}
@Override
public Map<?, ?> evaluate(DeferredObject[] arguments) throws HiveException {
Object mapObj = arguments[0].get();
Map<?, ?> map = this.mapObjectInspector.getMap(mapObj);
int n = this.intObjectInspector.get(arguments[1].get());
Map<?, ?> ret = tailN(map, n);
return ret;
}
@Override
public String getDisplayString(String[] arguments) {
return "map_tail_n( " + Arrays.toString(arguments) + " )";
}
private Map<Object, Object> tailN(Map<?, ?> m, int n) {
final ObjectInspector keyInspector = mapObjectInspector.getMapKeyObjectInspector();
final TreeMap<Object, Object> tail = new TreeMap<Object, Object>();
for (Map.Entry<?, ?> e : m.entrySet()) {
Object k = ObjectInspectorUtils.copyToStandardObject(e.getKey(), keyInspector);
Object v = e.getValue();
tail.put(k, v);
}
if (tail.size() <= n) {
return tail;
}
TreeMap<Object, Object> ret = new TreeMap<Object, Object>();
for (int i = 0; i < n; i++) {
Object k = tail.lastKey();
Object v = tail.remove(k);
ret.put(k, v);
}
return ret;
}
}