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Transformations

The data received from the Source system might, at times, not be suitable to be replicated to the Destination database or data warehouse as is. Using Transformations in Hevo, you can prepare the data in multiple ways before loading it to the Destination. Read Data Transformation to know more about scenarios where you may need to transform your data.

Note: For any Transformation that is applied on an Event, a maximum of 10,000 child Events can be generated.


Prerequisites


Writing the Transformation

You can design and apply Transformations on Events and Event Types in two ways:

To change the Transformation method, click the More (More) icon in the Transformation canvas.

Transformations UI

Note: You cannot use both methods in the same Transformation. Also, Transformation of one type cannot be converted to the other automatically. If you switch from one method to the other, you need to rewrite the Transformation completely.


Testing the Transformation

Hevo retains the first few Events ingested from your Source as sample data, which enables you to test your Transformation code. Once you write or modify your Transformations, you can test them against these real sample Events.

To test your Transformation script:

  1. In the Transformations UI, click the Select Event Type drop-down, and select the Source Event Type on which you want to test the Transformation.

    Select Event Type

  2. Click GET SAMPLE. You receive an Event from the sample data that Hevo stores. No changes are applied till you deploy the Transformation.

  3. Click TEST to test the Transformation and view the results.

    Sample Event

Sometimes, if the data in the Source changes, you may not see sample Events for it immediately. Or, you may want to test an edge-case scenario but do not have a sample Event for it. In that case, you can paste a sample Event containing the changes and test your Transformation.

You can also test the Transformation on a random sample Event not specific to any Event Type.

Testing Transformations on failed Events

You can test any Transformation you have written to resolve failed Events directly within the Transformation page.

To do this:

  1. Click the Select Event Type drop-down.

  2. Enable the Events not Loaded option to view only the Event Types with failed Events.

  3. Select the required Event Type and click GET SAMPLE.

  4. Click TEST.

View sample failed Events


Deploying the Transformation

Once you have tested the Transformation, click DEPLOY. The Transformation is applied to all applicable incoming Events.

Deploy transformation

You can click RESET to return to the last deployed stage.

We would advise you to monitor the Failed Events for any failures due to the newly deployed code.


Transformation Version History

Hevo maintains a history of the last five versions of your deployed Transformation scripts and configurations. You can revert to the previous version of a script by selecting it from the displayed list.

Note: The restored Transformation script is in a Draft state. You should test this version before deploying it. The system warns you if you try to deploy it directly.

To view the history of the deployed Transformations and restore an earlier version, do the following:

  1. Click the More ( ) icon and and select Version History.

    View Version History

  2. From the VERSION HISTORY pane, select the version you want to restore, and then click RESTORE THIS VERSION.

    Restore This Version

  3. Click TEST and then DEPLOY to test and deploy the restored Transformation script.

    Test and Deploy

Note: The steps given above are for Drag and Drop Transformations. You can also restore a previous version of your Python code-based Transformation using similar steps.


Last updated on Aug 13, 2024

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