tFileOutputXML in Talend Map/Reduce Jobs - 6.1

Talend Components Reference Guide

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6.1
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Talend Big Data
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Data Governance
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Talend Studio

Warning

The information in this section is only for users that have subscribed to one of the Talend solutions with Big Data and is not applicable to Talend Open Studio for Big Data users.

In a Talend Map/Reduce Job, tFileOutputXML, as well as the whole Map/Reduce Job using it, generates native Map/Reduce code. This section presents the specific properties of tFileOutputXML when it is used in that situation. For further information about a Talend Map/Reduce Job, see the Talend Big Data Getting Started Guide.

Component family

MapReduce/Output

 

Basic settings

Property type

Either Built-In or Repository.

 

 

Built-In: No property data stored centrally.

 

Click this icon to open a database connection wizard and store the database connection parameters you set in the component Basic settings view.

For more information about setting up and storing database connection parameters, see Talend Studio User Guide.

 

 

Repository: Select the repository file where the properties are stored.

The properties are stored centrally under the Hadoop Cluster node of the Repository tree.

The fields that come after are pre-filled in using the fetched data.

For further information about the Hadoop Cluster node, see the Getting Started Guide.

 

Row tag

Specify the tag that will wrap data and structure per row.

 

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.

 

Folder

Browse to, or enter the path pointing to the data to be used in the file system.

This path must point to a folder rather than a file, because a Talend Map/Reduce Job need to write in its target folder not only the final result but also multiple part- files generated in performing Map/Reduce computations.

Note that you need to ensure you have properly configured the connection to the Hadoop distribution to be used in the Hadoop configuration tab in the Run view.

 

Action

Select an operation for writing data:

Create: Creates a file and write data in it.

Overwrite: Overwrites the file existing in the directory specified in the Folder field.

Advanced settingsRoot tags

Specify one or more root tags to wrap the whole output file structure and data. The default root tag is root.

 Output format

Define the output format.

  • Column: The columns retrieved from the input schema.

  • As attribute: select check box for the column(s) you want to use as attribute(s) of the parent element in the XML output.

Note

If the same column is selected in both the Output format table as an attribute and in the Use dynamic grouping setting as the criterion for dynamic grouping, only the dynamic group setting will take effect for that column.

Use schema column name: By default, this check box is selected for all columns so that the column labels from the input schema are used as data wrapping tags. If you want to use a different tag than from the input schema for any column, clear this check box for that column and specify a tag label between quotation marks in the Label field.

 

Use dynamic grouping

Select this check box if you want to dynamically group the output columns. Click the plus button to add one ore more grouping criteria in the Group by table.

Column: Select a column you want to use as a wrapping element for the grouped output rows.

Attribute label: Enter an attribute label for the group wrapping element, between quotation marks.

 

Encoding

Select the encoding from the list or select Custom and define it manually. This field is compulsory for database data handling.

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 in Map/Reduce Jobs

In a Talend Map/Reduce Job, it is used as an end component and requires a transformation component as input link. The other components used along with it must be Map/Reduce components, too. They generate native Map/Reduce code that can be executed directly in Hadoop.

Once a Map/Reduce Job is opened in the workspace, tFileOutputXML as well as the MapReduce family appears in the Palette of the Studio.

Note that in this documentation, unless otherwise explicitly stated, a scenario presents only Standard Jobs, that is to say traditional Talend data integration Jobs, and non Map/Reduce Jobs.

Hadoop Connection

You need to use the Hadoop Configuration tab in the Run view to define the connection to a given Hadoop distribution for the whole Job.

This connection is effective on a per-Job basis.