/// [MapArray] is physically a [crate::array::ListArray] that has a
/// [crate::array::StructArray] with 2 child fields.
pub struct MapArray {
    data: ArrayData,
    values: ArrayRef,
    value_offsets: RawPtrBox<i32>,
}

/// A Map is a logical nested type that is represented as
///
/// List<entries: Struct<key: K, value: V>>
///
/// In this layout, the keys and values are each respectively contiguous. We do
/// not constrain the key and value types, so the application is responsible
/// for ensuring that the keys are hashable and unique. Whether the keys are sorted
/// may be set in the metadata for this field.
///
/// In a field with Map type, the field has a child Struct field, which then
/// has two children: key type and the second the value type. The names of the
/// child fields may be respectively "entries", "key", and "value", but this is
/// not enforced.
///
/// Map
/// ```text
///   - child[0] entries: Struct
///     - child[0] key: K
///     - child[1] value: V
/// ```
/// Neither the "entries" field nor the "key" field may be nullable.
///
/// The metadata is structured so that Arrow systems without special handling
/// for Map can make Map an alias for List. The "layout" attribute for the Map
/// field must have the same contents as a List.
table Map {
  /// Set to true if the keys within each value are sorted
  keysSorted: bool;
}