Unique Rows (HashSet)

Description

The Unique Rows (HashSet) transform removes duplicate rows and filters only the unique rows as input data for the transform.

This transform differs from the Unique Rows pipeline transform by keeping track of the duplicate rows in memory and does not require a sorted input to process duplicate rows.

When using this transform on larger sets of data there is a risk of hash collisions unless "Compare using stored row values" is enabled.

This transform is not supported on the distributed pipeline engines: neither the Beam engines nor the native Spark engine. The hash set it uses to spot duplicates lives in the memory of a single worker, and these engines spread the rows over many workers, so duplicates that end up on different workers would survive. Both refuse the transform with an error rather than hand you that incomplete result.

Use a Memory Group By to get distinct rows instead: it is translated into the engine’s own grouping operation and covers the whole data set. On the native Spark engine Unique Rows is an option too, because that engine maps it onto its own distinct operation; on the Beam engines it is not, as it is refused there as well. See Getting started with Beam.

Options

Option	Description
Transform Name	Name of the transform this name has to be unique in a single pipeline.
Compare using stored row values	Select this option to store values for the selected fields in memory for every record. Storing row values requires more memory, but it prevents possible false positives if there are hash collisions.
Redirect duplicate row	Select this option to process duplicate rows as an error and redirect them to the error stream of the transform. If you do not select this option, the duplicate rows are deleted.
Error description	Specify the error handling description that displays when the transform detects duplicate rows. This description is only available when Redirect duplicate row is selected.
Fields to compare table	Specify the field names for which you want to find unique values. -OR- Select Get to insert all the fields from the input stream.

Option

Description

Transform Name

Name of the transform this name has to be unique in a single pipeline.

Compare using stored row values

Select this option to store values for the selected fields in memory for every record. Storing row values requires more memory, but it prevents possible false positives if there are hash collisions.

Redirect duplicate row

Select this option to process duplicate rows as an error and redirect them to the error stream of the transform. If you do not select this option, the duplicate rows are deleted.

Error description

Specify the error handling description that displays when the transform detects duplicate rows. This description is only available when Redirect duplicate row is selected.

Fields to compare table

Specify the field names for which you want to find unique values.

-OR-

Select Get to insert all the fields from the input stream.