When you create or edit a transform, the data grid displays a preview of results of the transform. Transform previews assist in specifying and validating the transformation steps before they are applied. Although final results may not be exactly represented, a preview gives a good indication of the changes.
When you review a preview, keep the following in mind:
- Previewed columns cannot be filtered or hidden.
- You cannot rename or change the data type of a previewed column until you add the change to your recipe.
- Selection of column headers is disabled.
For example, you want to remove leading and trailing quotation marks from all columns. You highlight the quotation marks in one cell and select a suggestion card for Replace:
Figure: Replace Suggestion Card
To replace in all columns, you click the third option. To verify that it is correct for your needs, you click Edit .
The transform preview displays in the data grid for each column to be modified:
Tip: The preview also contains updated data quality bars and column histograms. You can use them to test for changes on counts or column values.
Figure: Transform Preview for Replace
The transform preview displays for all valid transforms.
Tip: Press ESC to cancel a preview.
When you modify the transform in the Transform Builder, the preview is updated as you type.
- You can review the preview results using independent scroll bars in the transform preview.
- Previews of transforms are displayed next to each source column.
- You can apply filters to the preview through the filter drop-down. These filters persist after the preview is completed.
Preview color scheme:
| Color | Meaning |
|---|---|
| blue | matching data |
| yellow | updated data |
| green | unchanged data |
| red | deletions |
| blurred | transform is invalid |
An error might appear while you are typing the transform. Because the transform is not valid, the transform preview appears blurred and does not display the results of the transform.
Variations:
Previews vary depending on the type of transform. For example, if you create a transform to replace values in a column, the preview displays the results of that transform. If you create a transform to extract values from a column, the preview displays the values that will be extracted.
Split pane previews: For transforms that change the number of rows and columns, the results of the transform are previewed in a split pane view in the data grid and in the column browser. The following transform types are previewed in a split pane:- pivot
- deduplicate
- unpivot
Figure: Split Pane Preview