本章将介绍如何在系统中下载，安装和设置 Apache Pig 。

先决条件

在你运行Apache Pig之前，必须在系统上安装好Hadoop和Java。因此，在安装Apache Pig之前，请按照以下链接中提供的步骤安装Hadoop和Java://www.ogeek.cn/hadoop/hadoop_enviornment_setup.htm

下载Apache Pig

首先，从以下网站下载最新版本的Apache Pig:https://pig.apache.org/

步骤1

打开Apache Pig网站的主页。在News部分下，点击链接release page，如下面的快照所示。

步骤2

点击指定的链接后，你将被重定向到 Apache Pig Releases 页面。在此页面的Download部分下，单击链接，然后你将被重定向到具有一组镜像的页面。

步骤3

选择并单击这些镜像中的任一个，如下所示。

步骤4

这些镜像将带您进入 Pig Releases 页面。 此页面包含Apache Pig的各种版本。 单击其中的最新版本。

步骤5

在这些文件夹中，有发行版中的Apache Pig的源文件和二进制文件。下载Apache Pig 0.16， pig0.16.0-src.tar.gz 和 pig-0.16.0.tar.gz 的源和二进制文件的tar文件。

安装Apache Pig

下载Apache Pig软件后，按照以下步骤将其安装在Linux环境中。

步骤1

在安装了 Hadoop，Java和其他软件的安装目录的同一目录中创建一个名为Pig的目录。（在我们的教程中，我们在名为Hadoop的用户中创建了Pig目录）。

$ mkdir Pig

第2步

提取下载的tar文件，如下所示。

$ cd Downloads/ 
$ tar zxvf pig-0.15.0-src.tar.gz 
$ tar zxvf pig-0.15.0.tar.gz 

步骤3

将 pig-0.16.0-src.tar.gz 文件的内容移动到之前创建的 Pig 目录，如下所示。

$ mv pig-0.16.0-src.tar.gz/* /home/Hadoop/Pig/

配置Apache Pig

安装Apache Pig后，我们必须配置它。要配置，我们需要编辑两个文件 - bashrc和pig.properties 。

.bashrc文件

在 .bashrc 文件中，设置以下变量

• PIG_HOME 文件夹复制到Apache Pig的安装文件夹

• PATH 环境变量复制到bin文件夹

• PIG_CLASSPATH 环境变量复制到安装Hadoop的etc（配置）文件夹（包含core-site.xml，hdfs-site.xml和mapred-site.xml文件的目录）。

export PIG_HOME = /home/Hadoop/Pig
export PATH  = PATH:/home/Hadoop/pig/bin
export PIG_CLASSPATH = $HADOOP_HOME/conf

pig.properties文件

在Pig的 conf 文件夹中，我们有一个名为 pig.properties 的文件。在pig.properties文件中，可以设置如下所示的各种参数。

pig -h properties 

支持以下属性:

Logging: verbose = true|false; default is false. This property is the same as -v
       switch brief=true|false; default is false. This property is the same 
       as -b switch debug=OFF|ERROR|WARN|INFO|DEBUG; default is INFO.             
       This property is the same as -d switch aggregate.warning = true|false; default is true. 
       If true, prints count of warnings of each type rather than logging each warning.		 
		 
Performance tuning: pig.cachedbag.memusage=<mem fraction>; default is 0.2 (20% of all memory).
       Note that this memory is shared across all large bags used by the application.         
       pig.skewedjoin.reduce.memusagea=<mem fraction>; default is 0.3 (30% of all memory).
       Specifies the fraction of heap available for the reducer to perform the join.
       pig.exec.nocombiner = true|false; default is false.
           Only disable combiner as a temporary workaround for problems.         
       opt.multiquery = true|false; multiquery is on by default.
           Only disable multiquery as a temporary workaround for problems.
       opt.fetch=true|false; fetch is on by default.
           Scripts containing Filter, Foreach, Limit, Stream, and Union can be dumped without MR jobs.         
       pig.tmpfilecompression = true|false; compression is off by default.             
           Determines whether output of intermediate jobs is compressed.         
       pig.tmpfilecompression.codec = lzo|gzip; default is gzip.
           Used in conjunction with pig.tmpfilecompression. Defines compression type.         
       pig.noSplitCombination = true|false. Split combination is on by default.
           Determines if multiple small files are combined into a single map.         
			  
       pig.exec.mapPartAgg = true|false. Default is false.             
           Determines if partial aggregation is done within map phase, before records are sent to combiner.         
       pig.exec.mapPartAgg.minReduction=<min aggregation factor>. Default is 10.             
           If the in-map partial aggregation does not reduce the output num records by this factor, it gets disabled.
			  
Miscellaneous: exectype = mapreduce|tez|local; default is mapreduce. This property is the same as -x switch
       pig.additional.jars.uris=<comma seperated list of jars>. Used in place of register command.
       udf.import.list=<comma seperated list of imports>. Used to avoid package names in UDF.
       stop.on.failure = true|false; default is false. Set to true to terminate on the first error.         
       pig.datetime.default.tz=<UTC time offset>. e.g. +08:00. Default is the default timezone of the host.
           Determines the timezone used to handle datetime datatype and UDFs.
Additionally, any Hadoop property can be specified.

验证安装

通过键入version命令验证Apache Pig的安装。如果安装成功，你将获得Apache Pig的正式版本，如下所示。

$ pig –version 
 
Apache Pig version 0.16.0 (r1682971)  
compiled Jun 01 2015, 11:44:35