When you create a mapping in advanced mode, you can preview data for individual transformations to test the mapping logic. The preview job runs on an advanced cluster in an AWS or Azure cloud environment and uses on-demand instances.
You can preview data if there are no mapping validation errors in the selected transformation. A mapping in advanced mode shows preview data for the selected transformation.
You can't preview data for the following transformations:
•Sources that have binary fields
•Normalizer
•Router
•Hierarchy Processor with multiple output groups
•Target
Note: If the cluster is running many jobs, the preview job might be slow.
Running a preview job in advanced mode
Run a data preview job on the Preview panel of the selected transformation.
Before you run a data preview job, verify that there are no mapping validation errors in the selected transformation.
1 In the Mapping Designer, select a transformation.
2Open the Preview panel.
3Click Run Preview.
4 In the Run Preview wizard, enter the number of source rows to preview and the runtime environment to run the preview job.
The number that you enter applies to each source in the mapping. For example, if you select 10 rows and the mapping contains multiple sources, the preview job processes the first 10 rows in each source.
You can select up to 999,999,999 rows.
Warning: Selecting a large number of source rows can cause storage or performance issues on the Secure Agent machine.
5Select the Read Entire Source option if you're sure you want Data Integration to read all source data. Preview data may be slow to display if you have a large source data set. Target data will be limited based on the value entered in the Rows to Preview field.
6The Enable Upstream Preview option allows you to preview data for the selected transformation and upstream transformations. This option is enabled by default. Preview data may be slow to display if you have many upstream transformations.**
7Click Run Preview.
Data Integration displays the results in the Preview panel for the selected transformation.
You can monitor preview jobs on the My Jobs page in Data Integration and on the All Jobs and Running Jobs pages in Monitor. Data Integration names the preview job <mapping name>-<instance number>, for example, MyMapping_1. You can download the session log for a data preview job.
To restart a preview job, run the job again on the Preview panel. You cannot restart a data preview job on the My Jobs or All Jobs pages.
Note: If you preview data that has parameterized sources or transformations with complex fields on a local cluster, you can only specify an S3/ADLS staging directory.
Viewing preview results in advanced mode
Data Integration generates preview results for the selected transformation and stores preview results in the staging location for the advanced cluster.
Data Integration shows complex data cells as hyperlinks on the Preview page. When you click a hyperlink, the preview data appears in a separate panel. Preview results show null values for the job name, start time, end time, and job status columns.
Preview results for the Sequence transformation might not be consistent from one preview run to the next. For example when you set the initial value in the transformation to 1, you might get a result of 1, 2, 3, 4 the first time you run a preview. The second time you run a preview, you might get 2001, 2002, 2003, 2004.
If the selected transformation is available only in advanced mode or contains hierarchical data, Data Integration stores preview results in a JSON file. Otherwise, Data Integration stores preview results in a CSV file. Data Integration purges preview data every 30 minutes and deletes preview data when the cluster shuts down.
Note: When the preview results are in CSV format, null values for integer, double, string, and text data types show as empty.