Macro downcast_value

macro_rules! downcast_value {
    ($Value: expr, $Type: ident) => { ... };
    ($Value: expr, $Type: ident, $T: tt) => { ... };
}

Downcast an Arrow Array to a concrete type, return an DataFusionError::Internal if the cast is not possible. In normal usage of DataFusion the downcast should always succeed.

Example: let array = downcast_value!(values, Int32Array)