Function cast_output_field

datafusion/expr/src/expr_schema.rs:74–88

Derives the output field for a cast expression from the source field. For `TryCast`, `force_nullable` is `true` since a failed cast returns NULL.

(
    source_field: &FieldRef,
    target_type: &DataType,
    force_nullable: bool,
)

/// Derives the output field for a cast expression from the source field.
/// For `TryCast`, `force_nullable` is `true` since a failed cast returns NULL.
fn cast_output_field(
    source_field: &FieldRef,
    target_type: &DataType,
    force_nullable: bool,
) -> Arc<Field> {
    let mut f = source_field
        .as_ref()
        .clone()
        .with_data_type(target_type.clone())
        .with_metadata(source_field.metadata().clone());
    if force_nullable {
        f = f.with_nullable(true);
    }
    Arc::new(f)
}

impl ExprSchemable for Expr {
    /// Returns the [arrow::datatypes::DataType] of the expression