Adding or modifying fields by using different PDI steps

As you saw in the last Transformation, once the data is created in the first step, it travels from step to step through the hops that link those steps. The hop's function is just to direct data from an output buffer to an input one. The real manipulation of data, as well as the modification of a stream, by adding or removing fields, occurs in the steps. In the last Transformation that you created, you used the Calculator step to create new fields and add them to your dataset.

The Calculator step is one of the many steps that PDI has to create new fields. You create the fields from scratch or by combining existent ones. Usually, you will find these steps under the Transform category of the Steps tree. In the following table, you have descriptions of some of the most used steps. The examples reference the first Transformation you created in this chapter:

Note that some of these steps can be used for generating more than one field at a time; an example of that is the User Defined Java Expression step (or UDJE for short).

Any of these steps when added to your Transformation, is executed for every row in the stream. It takes the row, identifies the fields needed to do its tasks, calculates the new field(s), and adds it (or them) to the dataset.

For more details on a particular step, don't hesitate to visit the documentation for steps at https://help.pentaho.com/Documentation/8.0/Products/Data_Integration/Transformation_Step_Reference. Also, for all steps, there is a handy Help button in their configuration window.