Preserving and Removing Downstream Expressions

1. Delete a Component:
• When you need to delete a component (such as a datastore, transformation, or filter), select it in the logical diagram and either press the Delete key or right-click and choose Delete from the context menu.
2. Confirmation Dialog:
• After selecting Delete, a confirmation dialog will appear to confirm the deletion. This dialog gives you options on how to handle any downstream expressions related to the deleted component.
3. Check Box for Preserving or Removing Expressions:
• In the confirmation dialog, there is a checkbox labeled "Preserve downstream expressions".
• By default, ODI will preserve these expressions. This means that the expressions related to the component being deleted (e.g., data mappings, transformations) will not be lost, and any existing connections will remain intact.
4. What Are Downstream Expressions?
• Downstream expressions are the data mappings or transformations that were created as part of the data flow from one component to another.
• These expressions may include things like attribute mappings, filters, transformations, or any other logic added between components.
5. What Happens if You Preserve the Expressions?
• If you select the Preserve downstream expressions checkbox, ODI will retain the mappings or transformations created up to that point.
• For example, if you delete a connection between a source and a target datastore but want to preserve the mappings of attributes on the target datastore, the expressions (or mappings) from the source to the target will remain.
6. What Happens if You Remove the Expressions?
• If you uncheck the box to remove downstream expressions, all the mappings and transformations associated with the component will be deleted along with it.
• This option is useful if you want to start fresh and create new expressions or logic in place of the deleted component.
7. Example Scenario:
• Suppose a source datastore is connected to a target datastore with all the attributes mapped.
• You realize that you need to apply a filter to the data before it reaches the target. Instead of deleting both the source and target connections, you can delete the connection between them, preserve the expressions, and then insert the filter component between the source and target. The attribute mappings will remain intact, and no previous work will be lost.