NullValueIndex (druid-processing 28.0.1 API)

```
public interface NullValueIndex
```
Provides index for all null rows in a column, to use with IS/IS NOT NULL filters

- Method Summary
  
  All Methods Instance Methods Abstract Methods
  Modifier and Type Method Description
  
  BitmapColumnIndex get()

- Method Detail
  - get
```
BitmapColumnIndex get()
```