| Interface | Description | 
|---|---|
| Expression | Base class of the public logical expression API. | 
| Literal<T> | Represents a constant literal value in the public expression API. | 
| NamedReference | Represents a field or column reference in the public logical expression API. | 
| RewritableTransform | Allows Spark to rewrite the given references of the transform during analysis. | 
| SortOrder | Represents a sort order in the public expression API. | 
| Transform | Represents a transform function in the public logical expression API. | 
| Class | Description | 
|---|---|
| Cast | Represents a cast expression in the public logical expression API. | 
| Expressions | Helper methods to create logical transforms to pass into Spark. | 
| Extract | Represent an extract function, which extracts and returns the value of a
 specified datetime field from a datetime or interval value expression. | 
| GeneralScalarExpression | The general representation of SQL scalar expressions, which contains the upper-cased
 expression name and all the children expressions. | 
| Lit | Convenience extractor for any Literal. | 
| LogicalExpressions | Helper methods for working with the logical expressions API. | 
| NamedTransform | Convenience extractor for any Transform. | 
| Ref | Convenience extractor for any NamedReference. | 
| UserDefinedScalarFunc | The general representation of user defined scalar function, which contains the upper-cased
 function name, canonical function name and all the children expressions. | 
| Enum | Description | 
|---|---|
| NullOrdering | A null order used in sorting expressions. | 
| SortDirection | A sort direction used in sorting expressions. |