hive0.13的udtf使用例子

时间：2016-02-04 02:03:46 阅读：202 评论：0 收藏：0 [点我收藏+]

hive0.13的自定义UDTF函数的应用

代码的编写
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/**
 * 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 com.csm.data.udf.hive;

import java.util.ArrayList;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDTF;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.StructObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;

/**
 * 将一个字段，它的值为
 * 流行|90后|粤语|
 * 这样的字段，转换为
 * 流行
 * 90后
 * 粤语
 * 这样的三行
 * 本方法只能支持
 * select csm_explode(tag) from t_test这种单字段的形式
 * 
 */
@Description(name = "csm_explode", value = "_FUNC_(a) - separates the elements of string with ‘|‘   into multiple rows")
public class CSMUDTFExplode extends GenericUDTF {


	@Override
	public void close() throws HiveException {
	}

	@Override
	public StructObjectInspector initialize(ObjectInspector[] args)
			throws UDFArgumentException {
		if (args.length != 1) {
			throw new UDFArgumentException("csm_explode() takes only one argument");
		}

		ArrayList<String> fieldNames = new ArrayList<String>();
		ArrayList<ObjectInspector> fieldOIs = new ArrayList<ObjectInspector>();
		//返回的新列的字段名称
		fieldNames.add("tag");
		fieldOIs.add(PrimitiveObjectInspectorFactory.javaStringObjectInspector);
		return ObjectInspectorFactory.getStandardStructObjectInspector(
				fieldNames, fieldOIs);
	}


	@Override
	public void process(Object[] o) throws HiveException {
		String input = o[0].toString();
		String[] test = input.split("\\|");
		//forward处理一个数组，每个数组作为一行返回，每个数组里的元素作为一列
		for(int i =0 ;i < test.length;i ++){
			String[] tag = {test[i]};
			forward(tag);
		}
		
	}

	@Override
	public String toString() {
		return "";
	}
}

这个自定义函数最好是打包成一个单独的jar包，这个jar包需要指定一个有main函数的类作为默认的入口，虽然这个类用不上

写了一个ATest作为有main函数的类
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