Single Threader

The Single Threader step executes a sequence of steps in a single thread. This can help you tune performance by limiting the number of threads/processors used.

Common use cases include:

• Reducing overhead in transformations with many steps (for example, less data passing and thread context switching).
• Sorting rows within a specific time frame or row count for near-real-time streaming.
• Processing data in chunks, pausing, and then continuing after reaching a chunk size.

For more background, see White Paper on Single Threading in Pentaho Data Integration.

General

Field	Description
Step name	Unique name of the step on the canvas. Default is Single Threader.
Transformation	Sub-transformation to run in a single thread. Enter a path or select Browse.

If you select a transformation that shares the same root path as the current transformation, PDI automatically replaces the common root with ${Internal.Entry.Current.Directory}.

If you are working with a repository, specify the transformation by repository name; otherwise, specify the .ktr file path. |

Options tab

Single Threader Options tab

Option	Description
Injector step	Step that satisfies the Mapping Input Specifications (for example, filename, type, length, and precision). Enter a step name or select Get.
Retrieval step	Step from which data is retrieved. Enter a step name or select Get.
Batch size	Starts processing a chunk after N rows are received. Default is 100. You can use Batch time (ms) instead.
Batch time (ms)	Starts processing a chunk after the specified delay (instead of using Batch size).

Parameters tab

Single Threader Parameters tab

Use this tab to pass parameters to the sub-transformation.

Option	Description
Pass parameter values to sub transformation	Passes all parameter values from the parent transformation to the sub-transformation.
Parameter name	Parameter name passed to the sub-transformation.
Fixed value	Parameter value. You can set it as:

• a literal value (for example, Sub transformation)
• a variable or parameter (for example, ${Internal.Job.Name})
• a combination (for example, ${FILE_PREFIX}_${FILE_DATE}.txt) | | Get parameters | Retrieves parameters defined in the sub-transformation. |