# hive_udf

**Repository Path**: bravepig/hive_udf

## Basic Information

- **Project Name**: hive_udf
- **Description**: 创建UDF于UDAF
- **Primary Language**: Java
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2017-02-19
- **Last Updated**: 2020-12-19

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

### 1. MaxIntUDAF.java


```
package com.learn.h;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDAF;
import org.apache.hadoop.hive.ql.exec.UDAFEvaluator;
import org.apache.hadoop.io.IntWritable;

@Description(name="my_max",value="_FUNC_(Int) - Returns the maxinum value of Int number")
public class MaxIntUDAF extends UDAF{
	public static class MaxNumberIntUDAFEvaluator implements UDAFEvaluator {
		private IntWritable result;

		public void init() {
			result = null;
		}

		public boolean iterate(IntWritable value) {
			if (value ==null)
			{
				return false;
			}
			if (result==null)
			{
				result =new IntWritable(value.get());
			}
			else
			{
				 result.set(Math.max(result.get(), value.get()));
			}
			return true;
			
		}

		public IntWritable terminatePartial() {
			return result;
		}

		public boolean merge(IntWritable other) {
			return iterate(other);
		}

		public IntWritable terminate() {
			return result;
		}
	}

}

```

### 2. MD5HashUDF.java

```
package com.learn.h;

import org.apache.commons.codec.digest.DigestUtils;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;

@Description(name = "my_md5hash", value = "_FUNC_(str) - Returns the md5hex value of str")
public class MD5HashUDF extends UDF {
	public String evaluate(String in) {
		return DigestUtils.md5Hex(in);
	}

}

```

### 3. hive命令行中执行：上传jar到classpath

```
add jar xx.jar
```

### 4. hive命令行中执行：创建函数

```
 create temporary function my_md5hash as 'com.learn.h.MD5HashUDF';
 create temporary function my_max as 'com.learn.h.MaxIntUDAF';
```

### 5. hive命令行中执行：验证函数

```
select name,my_md5hash(name) from product;
select my_max(pid) from product;
```