IBM DataStage - Simple staging example¶

Model¶

Refer to the Source model.

Template¶

The template consists of the following DataStage job:

Source stage¶

Source stage (1/2)¶

Opening the Source properties notice that Data source and Table name contain placeholders.

Source stage (2/2)¶

In the Columns tab, there is a column named 'attribute_name' that has a section annotation in the description.

Transformer stage¶

Just as the columns tab in the source properties, the Transformer stage also contains a section annotation in the description of field attribute_name.

Target stage¶

Target stage (1/2)¶

The target stage contains a placeholder for Table name

Target stage (2/2)¶

The Columns tab again shows a column attribute_name with a section annotation for a section named "Attribute".

Documentation¶

For documentation on templates, please see Template.

Config¶

Enrich the model with DataStage datatypes using Model Attribute Injection¶

The model used as input for this example contains columns that are specified with a database-datatype (varchar, int, datetime etc). DataStage uses it's own set of datatypes. For the model to be used to map to a DataStage template, first the model needs to be enriched with DataStage datatype characteristics. This model enrichment is done using a specific CrossGenerate feature named Model Attribute Injection. This feature enables adding attributes to elements in the model.

Model Attribute Injection is configured in the first part of the config shown below: Each database datatype used in the model is mapped to its corresponding DataStage datatype. This DataStage datatype is stored in the etldatatype XML attribute of the model's attribute. The xml snippet below shows an example of Model Attribute Injection configuration.

<ModelAttributeInjection
  modelXPath="//attribute[@datatype='varchar']"
  targetAttribute="etldatatype"
  targetValue="12"
/>

Prepare the DataStage template job using Template Placeholder Injection¶

Before code can be generated using the DataStage template job and the enriched model, some attributes in the DataStage template that have concrete values need to be populated using a placeholder.

Add placeholders to a template using Template Placeholder Injection¶

When developing a template DataStage job, a lot of elements can be made abstract using DataStage Designer. This means that for table or column names, a DataStage job can be developed against an abstract datamodel. So the DataStage job is build using placeholder names, which automatically makes it a template (for example 'attribute_name').

Other elements, for example data types, length & precision cannot be made abstract; the IDE requires you to specify concrete, existing datatypes and lengths for columns. When applying a model to a template DataStage job, it is required that the data type, length and other characteristics are substituted from the model. This is only possible if the elements that need to be subsituted contain placeholders in the DataStage template job.

Template Placeholder Injections enables inserting placeholders in a template in parts that cannot be made abstract from the IDE. An example of a template placeholder injection is shown below:

<TemplatePlaceholderInjection 
    templateXPath="//SubRecord[Property/text()='attribute_name']/Property[@Name='SqlType']" 
    modelNode="etldatatype" 
    scope="current" 
/>

The example looks for all SubRecord elements that have a Property child element with value 'attribute_name' and for these SubRecord elements selects the Property child element that has Name Attribute with value 'SqlType'. For these elements the text value is populated with a placeholder referencing the etldatatype attribute from the model.

Specifying additional sections¶

As can be seen in the config below, there is a section defined named Entity that references DSExport/Job. This section is configured in the config instead of through an annotation in the DataStage Designer.

<Section 
    name="Entity" 
    templateXPath="DSExport/Job" 
/>

Full config example¶

<?xml version="1.0" encoding="UTF-8"?>
<XGenConfig>
  <Model>    
    <ModelAttributeInjections>
       <!-- set etl datatype -->
      <ModelAttributeInjection modelXPath="//attribute[@datatype='VARCHAR']" targetAttribute="etldatatype" targetValue="12"/>
      <ModelAttributeInjection modelXPath="//attribute[@datatype='NVARCHAR']" targetAttribute="etldatatype" targetValue="-9"/>      
      <ModelAttributeInjection modelXPath="//attribute[@datatype='INTEGER']" targetAttribute="etldatatype" targetValue="4"/>
      <ModelAttributeInjection modelXPath="//attribute[@datatype='DATE']" targetAttribute="etldatatype" targetValue="9"/>
      <ModelAttributeInjection modelXPath="//attribute[@datatype='DECIMAL']" targetAttribute="etldatatype" targetValue="3"/>
      <!-- set length and scale where needed -->
      <ModelAttributeInjection modelXPath="//attribute[@datatype='INTEGER']" targetAttribute="length" targetValue="0"/>
      <ModelAttributeInjection modelXPath="//attribute[@datatype='DATE']" targetAttribute="length" targetValue="0"/>
      <ModelAttributeInjection modelXPath="//attribute[@datatype='INTEGER']" targetAttribute="scale" targetValue="0"/>
      <ModelAttributeInjection modelXPath="//attribute[@datatype='DATE']" targetAttribute="scale" targetValue="0"/>
      <ModelAttributeInjection modelXPath="//attribute[@datatype='VARCHAR']" targetAttribute="scale" targetValue="0"/>
      <ModelAttributeInjection modelXPath="//attribute[@datatype='NVARCHAR']" targetAttribute="scale" targetValue="0"/>
      <ModelAttributeInjection modelXPath="//attribute[@datatype='decimal']" targetAttribute="length" targetXPath="./@precision"/>      
     </ModelAttributeInjections>
  </Model>
  <Template rootSectionName="System">
    <FileFormat type="IBM_DataStage" commentNodeXPath="Property[@Name=&quot;Description&quot;]" currentAccessor="_" childAccessor="$" templateType="xml" singleLineCommentPrefix="--" multiLineCommentPrefix="/*" multiLineCommentSuffix="*/" annotationPrefix="@XGen" annotationArgsPrefix="(" annotationArgsSuffix=")" />
    <Output type="output_per_element" />
    <Sections>
      <Section name="Entity" templateXPath="DSExport/Job" />
    </Sections>
    <TemplatePlaceholderInjections>
      <TemplatePlaceholderInjection templateXPath="//SubRecord[Property/text()='attribute_name']/Property[@Name='SqlType']" modelNode="etldatatype" scope="current" />
      <TemplatePlaceholderInjection templateXPath="//SubRecord[Property/text()='attribute_name']/Property[@Name='Precision']" modelNode="length" scope="current" />
      <TemplatePlaceholderInjection templateXPath="//SubRecord[Property/text()='attribute_name']/Property[@Name='Scale']" modelNode="scale" scope="current" />
    </TemplatePlaceholderInjections>
  </Template>
  <Binding>
    <SectionModelBinding section="System" modelXPath = "/modeldefinition/system" placeholderName="system">
      <SectionModelBinding section="Entity" modelXPath="mappableObjects/entity" placeholderName="entity">
        <Placeholders>
          <Placeholder name="system" modelXPath="../.." />                 
        </Placeholders>
        <SectionModelBinding section="Attribute" modelXPath="attributes/attribute" placeholderName="attribute">
          <Placeholders>
            <Placeholder name="system" modelXPath="../../../.." />
            <Placeholder name="entity" modelXPath="../.." />                 
          </Placeholders>    
                </SectionModelBinding>        
            </SectionModelBinding>
    </SectionModelBinding>    
  </Binding>
</XGenConfig>

Documentation¶

For documentation on the configuration, please see Config.

Output¶

When running CrossGenerate with the given model, template job and config, the result is a XML file containing the jobs for the Customer and Order tables specified in the model. The output of the Customer job is illustrated below:

Job¶

Notice that the stage names have been changed where the name contained a placeholder

Source stage¶

Source stage (1/2)¶

System and table names have been substituted for Data Source and Table name

Source stage (2/2)¶

The columns from the model have been substituted in the stage with the appropriate data type, length, etc.

Note

The section annotation is not present in the column's description anymore.

Transformer stage¶

The transformer stage also has the columns from the model substituted.

Target stage¶

Table and columns are substituted in the target stage.