> For the complete documentation index, see [llms.txt](https://docs.pentaho.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.pentaho.com/pdia-data-integration/9.3-data-integration/pdi-transformation-steps-reference-overview/unique-rows/select-an-engine-unique-rows.md).

# Select an engine

You can run the Unique Rows step on the Pentaho engine or on the Spark engine.

The input stream must be sorted in a step prior to the Unique Rows step; otherwise, only consecutive double rows will be correctly analyzed and filtered. However, the rows do not have to be pre-sorted if you use the [Unique Rows (HashSet)](https://github.com/pentaho/documentation/blob/main/PDIA/9.3/PDI/Transformation%20steps/PDI%20transformation%20steps%20reference%20\(overview\)/Unique%20Rows%20\(HashSet\)=GUID-3D3F41A3-F02F-45A5-8FA5-FEF941A37555=6=en=.md) step, or if you use the Spark engine ([Spark Engine](broken://pages/muBxdVWTJHA6Xlhx8S1d)) to run the transformation.

Depending on your selected engine, the transformation runs differently. Select one of the following options to view how to set up the Unique Rows step for your selected engine:

* [Using the Unique Rows step on the Pentaho engine](/pdia-data-integration/9.3-data-integration/pdi-transformation-steps-reference-overview/unique-rows/select-an-engine-unique-rows/using-the-unique-rows-step-on-the-pentaho-engine.md): Learn how to set up this step when using the Pentaho engine.
* [Using the Unique Rows step on the Spark engine](/pdia-data-integration/9.3-data-integration/pdi-transformation-steps-reference-overview/unique-rows/select-an-engine-unique-rows/using-the-unique-rows-step-on-the-spark-engine.md): Learn how to set up this step when using the Spark engine.

For instructions on selecting an engine for your transformation, see [Run configurations](/pdia-data-integration/9.3-data-integration/data-integration-perspective-in-the-pdi-client/work-with-transformations-cp/run-your-transformation/run-configurations-work-with-transformations.md)


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.pentaho.com/pdia-data-integration/9.3-data-integration/pdi-transformation-steps-reference-overview/unique-rows/select-an-engine-unique-rows.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.