Trait datafusion::common::ExprSchema

pub trait ExprSchema: Debug {
    // Required methods
    fn nullable(&self, col: &Column) -> Result<bool, DataFusionError>;
    fn data_type(&self, col: &Column) -> Result<&DataType, DataFusionError>;
    fn metadata(
        &self,
        col: &Column
    ) -> Result<&HashMap<String, String>, DataFusionError>;
    fn data_type_and_nullable(
        &self,
        col: &Column
    ) -> Result<(&DataType, bool), DataFusionError>;
}

Provides schema information needed by certain methods of Expr (defined in the datafusion-common crate).

Note that this trait is implemented for &DFSchema which is widely used in the DataFusion codebase.

Required Methods

fn nullable(&self, col: &Column) -> Result<bool, DataFusionError>

Is this column reference nullable?

fn data_type(&self, col: &Column) -> Result<&DataType, DataFusionError>

What is the datatype of this column?

fn metadata( &self, col: &Column ) -> Result<&HashMap<String, String>, DataFusionError>

Returns the column’s optional metadata.

fn data_type_and_nullable( &self, col: &Column ) -> Result<(&DataType, bool), DataFusionError>

Return the coulmn’s datatype and nullability

Implementors

impl ExprSchema for DFSchema

impl<P> ExprSchema for P

where P: AsRef<DFSchema> + Debug,