August 16, 2023

tPigCode – Docs for ESB 6.x

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tPigCode

Extends the functionalities of a
Talend
 Job through using Pig scripts.

The tPigCode enters personalized Pig code to integrate
it in
Talend
 program. You can execute this code only once.

tPigCode Standard properties

These properties are used to configure tPigCode running in the Standard Job framework.

The Standard
tPigCode component belongs to the Big Data and the Processing families.

The component in this framework is available when you are using one of the Talend solutions with Big Data.

Basic settings

Schema and Edit
Schema

A schema is a row description. It defines the number of fields (columns) to
be processed and passed on to the next component. The schema is either Built-In or stored remotely in the Repository.

Click Edit schema to make changes to the schema.
If the current schema is of the Repository type, three
options are available:

  • View schema: choose this option to view the
    schema only.

  • Change to built-in property: choose this
    option to change the schema to Built-in for
    local changes.

  • Update repository connection: choose this
    option to change the schema stored in the repository and decide whether to propagate
    the changes to all the Jobs upon completion. If you just want to propagate the
    changes to the current Job, you can select No
    upon completion and choose this schema metadata again in the [Repository Content] window.

 

Built-In: You create and store the
schema locally for this component only. Related topic: see
Talend Studio

User Guide.
 

Repository: You have already created
the schema and stored it in the Repository. You can reuse it in various projects and
Job designs. Related topic: see
Talend Studio

User Guide.

Scripts

Type in Pig scripts you want to execute depending on the task you
need to perform. For further information about Pig functions syntax,
see Apache’s documentation about Pig UDF:

http://pig.apache.org

Pig components output tuples and automatically set up an alias for
each tuple. When you use a tuple in your Pig script, you have to
enter the right alias.

The alias syntax is Component_ID_rowID_Result, for
example, tPigCode_1_row2_Result.

Advanced settings

tStatCatcher Statistics

Select this check box to gather the Job processing metadata at the
Job level as well as at each component level.

Enable escape

Select this check box so that you can simply write plain Pig code
in the Scripts field without need
to bear in mind the escape characters, otherwise required for proper
Java code generation.

Global Variables

Global Variables

ERROR_MESSAGE: the error message generated by the
component when an error occurs. This is an After variable and it returns a string. This
variable functions only if the Die on error check box is
cleared, if the component has this check box.

A Flow variable functions during the execution of a component while an After variable
functions after the execution of the component.

To fill up a field or expression with a variable, press Ctrl +
Space to access the variable list and choose the variable to use from it.

For further information about variables, see
Talend Studio

User Guide.

Usage

Usage rule

This component is commonly used as intermediate step together with
input component and output component.

A tPigCode component can execute
only one Pig Latin statement, therefore, if you need to execute
multiple statements, you have to use a corresponding number of
tPigCode components to run
them, one after another.

If a particular .jar file is required to execute a statement, you
need to register that library file via the tPigLoad component that starts the Pig process in
question.

Prerequisites

The Hadoop distribution must be properly installed, so as to guarantee the interaction
with
Talend Studio
. The following list presents MapR related information for
example.

  • Ensure that you have installed the MapR client in the machine where the Studio is,
    and added the MapR client library to the PATH variable of that machine. According
    to MapR’s documentation, the library or libraries of a MapR client corresponding to
    each OS version can be found under MAPR_INSTALL
    hadoophadoop-VERSIONlib
    ative    . For example, the library for
    Windows is lib
    ativeMapRClient.dll     in the MapR
    client jar file. For further information, see the following link from MapR: http://www.mapr.com/blog/basic-notes-on-configuring-eclipse-as-a-hadoop-development-environment-for-mapr.

    Without adding the specified library or libraries, you may encounter the following
    error: no MapRClient in java.library.path.

  • Set the -Djava.library.path argument, for example, in the Job Run VM arguments area
    of the Run/Debug view in the [Preferences] dialog box in the Window menu. This argument provides to the Studio the path to the
    native library of that MapR client. This allows the subscription-based users to make
    full use of the Data viewer to view locally in the
    Studio the data stored in MapR.

For further information about how to install a Hadoop distribution, see the manuals
corresponding to the Hadoop distribution you are using.

Limitation

Knowledge of Pig scripts is required.

Scenario: Selecting a column of data from an input file and store it into a local
file

This scenario applies only to a Talend solution with Big Data.

This scenario describes a three-component Job that selects a column of data that
matches filter condition defined in tPigCode and stores
the result into a local file.

use_case_tpigcode1.png

Setting up the Job

  1. Drop the following components from the Palette to the design workspace: tPigCode, tPigLoad,
    tPigStoreResult.
  2. Right-click tPigLoad to connect it to
    tPigCode using a Row > Pig Combine connection.
  3. Right-click tPigCode to connect it to
    tPigStoreResult using a Row > Pig Combine connection.

Loading the data

  1. Double-click tPigLoad to open its
    Basic settings view.

    use_case_tpigcode2.png

  2. Click the three-dot button next to Edit
    schema     to add columns for tPigLoad.

    use_case_tpigcode3.png

  3. Click the plus button to add Name,
    Country and Age and click
    OK to save the setting.
  4. Select Local from the Mode area.
  5. Fill in the Input filename field with the
    full path to the input file.

    In this scenario, the input file is CustomerList
    which contains rows of names, country names and age.
  6. Select PigStorage from the Load function list.
  7. Leave rest of the settings as they are.

Configuring the tPigCode component

  1. Double-click tPigCode component to open
    its Basic settings view.

    use_case_tpigcode4.png

  2. Click Sync columns to retrieve the schema
    structure from the preceding component.
  3. Fill in the Script Code field with
    following expression:

    This
    filter expression selects column Name from
    CustomerList.

Saving the result data to a local file

  1. Double-click tPigStoreResult to open its
    Basic settings view.

    use_case_tpigcode5.png

  2. Click Sync columns to retrieve the schema
    structure from the preceding component.
  3. Fill in the Result file field with the
    full path to the result file.

    In this scenario, the result is saved in Result
    file.
  4. Select Remove result directory if
    exists    .
  5. Select PigStorage from the Store function list.
  6. Leave rest of the settings as they are.

Executing the Job

Save your Job and press F6 to run it.

use_case_tpigcode6.png

The Result file is generated containing the selected column
of data.

Document get from Talend https://help.talend.com
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Docs 6.x
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