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Pig 作业配置__作业_用户指南_E-MapReduce-阿里云

E-MapReduce 中，用户申请集群的时候，默认为用户提供了 Pig 环境，用户可以直接使用 Pig 来创建和操作自己的表和数据。操作步骤如下。

1. 用户需要提前准备好 Pig 的脚本，例如：

    ```shell
    /*
    * 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
    *
    *     https://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.
    */
    -- Query Phrase Popularity (Hadoop cluster)
    -- This script processes a search query log file from the Excite search engine and finds search phrases that occur with particular high frequency during certain times of the day. 
    -- Register the tutorial JAR file so that the included UDFs can be called in the script.
    REGISTER oss://emr/checklist/jars/chengtao/pig/tutorial.jar;
    -- Use the  PigStorage function to load the excite log file into the “raw” bag as an array of records.
    -- Input: (user,time,query) 
    raw = LOAD 'oss://emr/checklist/data/chengtao/pig/excite.log.bz2' USING PigStorage('t') AS (user, time, query);
    -- Call the NonURLDetector UDF to remove records if the query field is empty or a URL. 
    clean1 = FILTER raw BY org.apache.pig.tutorial.NonURLDetector(query);
    -- Call the ToLower UDF to change the query field to lowercase. 
    clean2 = FOREACH clean1 GENERATE user, time, org.apache.pig.tutorial.ToLower(query) as query;
    -- Because the log file only contains queries for a single day, we are only interested in the hour.
    -- The excite query log timestamp format is YYMMDDHHMMSS.
    -- Call the ExtractHour UDF to extract the hour (HH) from the time field.
    houred = FOREACH clean2 GENERATE user, org.apache.pig.tutorial.ExtractHour(time) as hour, query;
    -- Call the NGramGenerator UDF to compose the n-grams of the query.
    ngramed1 = FOREACH houred GENERATE user, hour, flatten(org.apache.pig.tutorial.NGramGenerator(query)) as ngram;
    -- Use the  DISTINCT command to get the unique n-grams for all records.
    ngramed2 = DISTINCT ngramed1;
    -- Use the  GROUP command to group records by n-gram and hour. 
    hour_frequency1 = GROUP ngramed2 BY (ngram, hour);
    -- Use the  COUNT function to get the count (occurrences) of each n-gram. 
    hour_frequency2 = FOREACH hour_frequency1 GENERATE flatten($0), COUNT($1) as count;
    -- Use the  GROUP command to group records by n-gram only. 
    -- Each group now corresponds to a distinct n-gram and has the count for each hour.
    uniq_frequency1 = GROUP hour_frequency2 BY group::ngram;
    -- For each group, identify the hour in which this n-gram is used with a particularly high frequency.
    -- Call the ScoreGenerator UDF to calculate a "popularity" score for the n-gram.
    uniq_frequency2 = FOREACH uniq_frequency1 GENERATE flatten($0), flatten(org.apache.pig.tutorial.ScoreGenerator($1));
    -- Use the  FOREACH-GENERATE command to assign names to the fields. 
    uniq_frequency3 = FOREACH uniq_frequency2 GENERATE $1 as hour, $0 as ngram, $2 as score, $3 as count, $4 as mean;
    -- Use the  FILTER command to move all records with a score less than or equal to 2.0.
    filtered_uniq_frequency = FILTER uniq_frequency3 BY score > 2.0;
    -- Use the  ORDER command to sort the remaining records by hour and score. 
    ordered_uniq_frequency = ORDER filtered_uniq_frequency BY hour, score;
    -- Use the  PigStorage function to store the results. 
    -- Output: (hour, n-gram, score, count, average_counts_among_all_hours)
    STORE ordered_uniq_frequency INTO 'oss://emr/checklist/data/chengtao/pig/script1-hadoop-results' USING PigStorage();
    ```

2. 将该脚本保存到一个脚本文件中，例如叫 script1-hadoop-oss.pig，然后将该脚本上传到 OSS 的某个目录中（例如：oss://path/to/script1-hadoop-oss.pig）。

3. 进入阿里云 E-MapReduce 控制台作业列表。

4. 单击该页右上角的创建作业，进入创建作业页面。

5. 填写作业名称。

6. 选择 Pig 作业类型，表示创建的作业是一个 Pig 作业。这种类型的作业，其后台实际上是通过以下的方式提交。

    pig [user provided parameters]

7. 在应用参数选项框中填入 Pig 命令后续的参数。例如，如果需要使用刚刚上传到 OSS 的 Pig 脚本，则填写如下：

    -x mapreduce ossref://emr/checklist/jars/chengtao/pig/script1-hadoop-oss.pig

   您也可以单击选择 OSS 路径，从 OSS 中进行浏览和选择，系统会自动补齐 OSS 上 Pig 脚本的绝对路径。请务必将 Pig 脚本的前缀修改为 ossref（单击切换资源类型），以保证 E-MapReduce 可以正确下载该文件。

8. 选择执行失败后策略。

9. 单击确定，Pig 作业即定义完成。

最后更新：2016-11-23 16:03:59

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