Trait datafusion::common::ExprSchema
source · 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>;
}
Expand description
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§
sourcefn nullable(&self, col: &Column) -> Result<bool, DataFusionError>
fn nullable(&self, col: &Column) -> Result<bool, DataFusionError>
Is this column reference nullable?
sourcefn data_type(&self, col: &Column) -> Result<&DataType, DataFusionError>
fn data_type(&self, col: &Column) -> Result<&DataType, DataFusionError>
What is the datatype of this column?
sourcefn metadata(
&self,
col: &Column
) -> Result<&HashMap<String, String>, DataFusionError>
fn metadata( &self, col: &Column ) -> Result<&HashMap<String, String>, DataFusionError>
Returns the column’s optional metadata.
sourcefn data_type_and_nullable(
&self,
col: &Column
) -> Result<(&DataType, bool), DataFusionError>
fn data_type_and_nullable( &self, col: &Column ) -> Result<(&DataType, bool), DataFusionError>
Return the coulmn’s datatype and nullability