(Optional) Use MapReduce - Quick Start| Alibaba Cloud Documentation Center

(Optional) Use MapReduce

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Last Updated: Mar 18, 2020 Edit in GitHub

This topic describes how to compile and run the MapReduce WordCount example program after you install the MaxCompute client.

Note Maven users can search odps-sdk-mapred at Maven library to download the preferred Java SDK (available in different versions). The configuration information is as follows:

<dependency>
    <groupId>com.aliyun.odps</groupId>
    <artifactId>odps-sdk-mapred</artifactId>
    <version>0.26.2-public</version>
</dependency>

Prerequisites

JDK1.6 or a later version is installed.
The MaxCompute client is deployed by following the instructions provided in Install and configure the odpscmd client. For more information, see Client.

Procedure

After installing and configuring the client, open odpscmd.bat and enter the corresponding project space.
Run the following statements to create input and output tables:
```
CREATE TABLE wc_in (key STRING, value STRING);
CREATE TABLE wc_out (key STRING, cnt BIGINT);
-- Create input and output tables.
```
For more information about table creation statements, see Table operations.
Upload data by using either of the following methods:
- Use the Tunnel command, for example:
```
tunnel upload kv.txt wc_in
-- Upload example data.
```
  The data in the kv.txt file is as follows:
```
238,val_238
186,val_86
186,val_86
```
- Insert data by running an SQL statement, for example:
```
insert into table wc_in select '238',' val_238' from (select count(*) from wc_in) a;
```
Compile the MapReduce program and upload it to the MaxCompute client.
In this topic, Eclipse-based MapReduce program development is used as an example. MaxCompute provides local MapReduce debugging (which you can use alongside MaxCompute Studio). These methods can help you to quickly develop MapReduce programs.

You must create a MaxCompute project in Eclipse first, and then compile the MapReduce program (a .jar package, for example, Word-count-1.0.jar). After the local debugging is performed successfully, upload the compiled program to MaxCompute.
Add the .jar package to the project by running the following command:
```
add jar word-count-1.0.jar;
```

In the MaxCompute client, run the following command:

jar -resources word-count-1.0.jar -classpath /home/resources/word-count-1.0.jar com.taobao.jingfan.WordCount wc_in wc_out;

In the MaxCompute client, check the results by running the following command:
```
select * from wc_out;
```
Note If any resource is used in a Java program, you must add the resource to the -resources parameter. For more information about JAR commands, see Commands.