Transform (druid-processing 28.0.0 API)

All Known Implementing Classes:

ExpressionTransform
```
public interface Transform
```
A row transform that is part of a TransformSpec. Transforms allow adding new fields to input rows. Each one has a "name" (the name of the new field) which can be referred to by DimensionSpecs, AggregatorFactories, etc. Each also has a "row function", which produces values for this new field based on looking at the entire input row. If a transform has the same name as a field in an input row, then it will shadow the original field. Transforms that shadow fields may still refer to the fields they shadow. This can be used to transform a field "in-place". Transforms do have some limitations. They can only refer to fields present in the actual input rows; in particular, they cannot refer to other transforms. And they cannot remove fields, only add them. However, they can shadow a field with another field containing all nulls, which will act similarly to removing the field.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`String`	`getName()`	Returns the field name for this transform.
`Set<String>`	`getRequiredColumns()`	Returns the names of all columns that this transform is going to read.
`RowFunction`	`getRowFunction()`	Returns the function for this transform.

- Method Detail
  - getName
```
String getName()
```
    Returns the field name for this transform.
  - getRowFunction
```
RowFunction getRowFunction()
```
    Returns the function for this transform. The RowFunction takes an entire row as input and returns a column value as output.
  - getRequiredColumns
```
Set<String> getRequiredColumns()
```
    Returns the names of all columns that this transform is going to read.