Hadoop Apache Pig Execution Types

Pig has two EXECUTION TYPES or run modes, local and Hadoop (currently called MapReduce)

1. Local mode
2. Map Reduce mode.

1) Local mode

•  In Local mode, pig runs in a single JVM and accesses the local file system.
•  This mode is suitable only for small data sets and typing out pig.
•  To run in local mode, set the option to local i.e

%pig-x local
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2) Map Reduce Mode

• In Map Reduce mode, pig translates queries into map reduce jobs and runs them on a Hadoop cluster and cluster may be a pseudo or fully distributed cluster.
• To use Map Reduce mode, we have to check the version of pig that is compatible with the versions of Hadoop
• Pig honors the HADOOP-HOME environmental variable for finding which Hadoop client to run and a pig will also use a bundled copy of the Hadoop libraries.
• For pig, we have to set two properties in pig properties file which is pig’s cong directory.

i.e for pseudo distributed setup, an example is

fs.default.name=hdfs://localhost/
mapped. job. tracker=local host:8021

Once you have configured pig to connect to Hadoop cluster, you can launch pig, setting the  -x option to map reduce or a map-reduce mode is default i.e. % pig grunt>

Running Pig Programs

This section shows you how to run Pig in local mode, using the Grunt shell, a Pig script, and an embedded program.

There are three ways of executing pig programs which work in both local and map reduce mode.

1. Script-pig can run a script file that contains pig commands

2. Grunt – Is an interactive shell for running pig commands

3. Embedded – you can run pig programs from Java using the pig server class, much like you can use JDBC to run SQL Programs from JAVA.

Modes of Execution in Pig

You can execute Pig Latin statements.

1. Grunt shell or command line
2. Local mode or Map Reduce mode
3. Either Interactively or in a batch

Local mode and MR or HDFS Mode

In the local mode execution of pig, we expect all the inputs from the local environment (input from the local mode and produce the output from the local mode but should not be from HDFS)

Syntax:- Pig-x local.