The labels are associated with load, extract, and query jobs, and you can attach a label for each transformation. You can use labels to organize and filter the associated jobs in the Google Cloud Platform Log Explorer.
The label name can contain only lowercase letters, numeric characters, underscores, and dashes. If the label name includes any other characters, the mapping fails.
You can apply only one label for each transformation. When you create a transformation in a mapping, the label is optional.
You can parameterize the label. To use the current task name as the label, set the label to $CurrentTaskName.
In a mapping enabled with source SQL ELT optimization and multiple sources, the label is assigned to all sources. However, the label value from the first source is only used.