Function mz_repr::row::encoding2::array_to_decoder

fn array_to_decoder(
    array: &Arc<dyn Array>,
    col_ty: &ScalarType,
) -> Result<DatumColumnDecoder, Error>

Small helper function to downcast from an array to a DatumColumnDecoder.

Note: it is super important that we downcast as few times as possible. Datum encoding is a very hot path and downcasting is relatively slow