E-MapReduce 中,使用者申請叢集的時候,預設為使用者提供了 Pig 環境,使用者可以直接使用 Pig 來建立和操作自己的表和資料。
操作步驟
- 使用者需要提前準備好 Pig 的指令碼,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 * * 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. */ -- 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(); ```
- 將該指令碼儲存到一個指令檔中,例如叫 script1-hadoop-oss.pig,然後將該指令碼上傳到 OSS 的某個目錄中(例如:oss://path/to/script1-hadoop-oss.pig)。
- 進入阿里雲 E-MapReduce 控制台作業列表。
- 單擊該頁右上方的建立作業,進入建立作業頁面。
- 填寫作業名稱。
- 選擇 Pig 作業類型,表示建立的作業是一個 Pig 作業。這種類型的作業,其後台實際上是通過以下的方式提交。
pig [user provided parameters]
- 在應用參數選項框中填入 Pig 命令後續的參數。例如,如果需要使用剛剛上傳到 OSS 的 Pig 指令碼,則填寫如下:
-x mapreduce ossref://emr/checklist/jars/chengtao/pig/script1-hadoop-oss.pig
您也可以單擊選擇 OSS 路徑,從 OSS 中進行瀏覽和選擇,系統會自動補齊 OSS 上 Pig 指令碼的絕對路徑。請務必將 Pig 指令碼的首碼修改為 ossref(單擊切換資源類型),以保證 E-MapReduce 可以正確下載該檔案。
- 選擇執行失敗後策略。
- 單擊確定,Pig 作業即定義完成。