Metadata Injection
- Description
- Options

Metadata Injection

Description

The Metadata Injection transform inserts data from various sources into a pipeline at runtime.

This is typically used to automate repetitive ETL tasks.

For example, you might have a simple pipeline to load transaction data values from a supplier, filter specific values, and output them to a file. If you have more than one supplier, you would need to run this simple pipeline for each supplier. Yet, with metadata injection, you can expand this simple repetitive pipeline by inserting metadata from another pipeline that contains the ETL Metadata Injection transform. This transform coordinates the data values from the various inputs through the metadata you define. This process reduces the need for you to adjust and run the repetitive pipeline for each specific input.

The repetitive pipeline is known as the template pipeline. The template pipeline is called by the ETL Metadata Injection transform. You will create a pipeline to prepare what common values you want to use as metadata and inject these specific values through the ETL Metadata Injection transform.

We recommend the following basic procedure for using this transform to inject metadata:

Optimize your data for injection, such as preparing folder structures and inputs.
Develop pipelines for the repetitive process (the template pipeline), for metadata injection through the ETL Metadata Injection transform, and for handling multiple inputs.

The metadata is injected into the template pipeline through any transform that supports metadata injection.

Options

General

Option	Description
Transform name	Name of the transform.
Pipeline	Specify your template pipeline by entering in its path. Click Browse to display and enter the path details using the Virtual File System Browser. If you select a pipeline that has the same root path as the current pipeline, the variable ${Internal.Transform.Current.Directory} will automatically be inserted in place of the common root path. For example, if the current pipeline’s path is /home/admin/pipeline.hpl and you select a pipeline in the folder /home/admin/path/sub.hpl then the path will automatically be converted to ${Internal.Transform.Current.Directory}/path/sub.hpl.

Option

Description

Transform name

Name of the transform.

Pipeline

Specify your template pipeline by entering in its path. Click Browse to display and enter the path details using the Virtual File System Browser.

If you select a pipeline that has the same root path as the current pipeline, the variable ${Internal.Transform.Current.Directory} will automatically be inserted in place of the common root path. For example, if the current pipeline’s path is /home/admin/pipeline.hpl and you select a pipeline in the folder /home/admin/path/sub.hpl then the path will automatically be converted to ${Internal.Transform.Current.Directory}/path/sub.hpl.

The ETL Metadata Injection transform features the two tabs with fields. Each tab is described below.

Inject Metadata Tab

Option	Description
Target injection transform key	Lists the available fields in each transform of the template pipeline that can be injected with metadata.
Target description	Describes how the target fields relate to their target transforms.
Source transform	Lists the transform associated with the fields to be injected into the target fields as metadata.
Source field	Lists the fields to be injected into the target fields as metadata.

To specify the source field as metadata to be injected, perform the following transforms:

In the Target injection transform key column, double-click the field for which you want to specify a source field. The Source field dialog box opens.
Select a source field and click OK.
Optionally, select Use constant value to specify a constant value for the injected metadata through one of the following actions:
- Manually entering a value.
- Using an internal variable to set the value (${Internal.transform.Unique.Count} for example).
- Using a combination of manually specified values and parameter values (${FILE_PREFIX}_${FILE_DATE}.txt for example).

When specifying constant values for grouped lists of values like fields or filenames please note that there isn’t a good solution for that. Best practice is to use a Data Grid transform to inject a complete set of constant values. You can map those in this metadata injection transform. It will do its best to accommodate you by allowing you to inject a single row in the group with the specified constant value.

Injecting Metadata into the ETL Metadata Injection transform

For injecting metadata into the ETL Metadata Injection transform itself, the following exceptions apply:

To inject a method for how to specify a field (such as by FILENAME), set a PIPELINE_SPECIFICATION_METHOD constant to the field of an input transform. You can then map the field as a source to the PIPELINE_SPECIFICATION_METHOD constant in the ETL Metadata Injection transform.
The target field for the ETL Metadata Injection transform inserting the metadata into the original injection is defined by [GROUP NAME].[FIELD NAME]. For example, if the GROUP NAME is ‘OUTPUT_FIELDS’ and the FIELD NAME is ‘OUTPUT_FIELDNAME’, you would set the target field to ‘OUTPUT_FIELDS.OUTPUT_FIELDNAME’.

Options Tab

Option	Description
transform to read from (optional)	Optionally, select a transform in your template pipeline to pass data directly to a transform following the ETL Metadata Injection transform in your current pipeline.
Field name	If transform to read from is selected, enter the name of the field passed directly from the transform in the template pipeline.
Type	If transform to read from is selected, select the type of the field passed directly from the transform in the template pipeline.
Length	If transform to read from is selected, enter the length of the field passed directly from the transform in the template pipeline.
Precision	If transform to read from is selected, enter the precision of the field passed directly from the transform in the template pipeline.
Optional target file (hpl after injection)	For initial pipeline development or debugging, specify an optional file for creating and saving a pipeline of your template after metadata injection occurs. The resulting pipeline will be your template pipeline with the metadata already injected as constant values.
Streaming source transform	Select a source transform in your current pipeline to directly pass data to the Streaming target transform in the template pipeline.
Streaming target transform	Select the target transform in your template pipeline to receive data directly from the Streaming source transform.
Run resulting pipeline	Select to inject metadata and run the template pipeline. If this option is not selected, metadata injection occurs, but the template pipeline does not run.