paleolimbot commented on code in PR #8673:
URL: https://github.com/apache/arrow-rs/pull/8673#discussion_r2536358880
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parquet-variant-compute/src/variant_array.rs:
##########
@@ -733,6 +736,91 @@ impl From<ShreddedVariantFieldArray> for StructArray {
}
}
+/// A typed array reference that pairs an [`ArrayRef`] with its [`Field`]
metadata.
+///
+/// This struct is used to represent the `typed_value` field in shredded
variant arrays,
+/// where we need to preserve both the array data and its field metadata (such
as field
+/// name, data type, nullability, and extension type information).
+///
+/// The separation of array data and field metadata allows for proper handling
of:
+/// - Field names when working with struct fields
+/// - Nullability information for proper null handling
+/// - Extension type metadata (e.g., UUID extension on FixedSizeBinary)
+/// - Data type information for casting and validation
+#[derive(Debug, Clone)]
+pub struct TypedArrayRef {
+ inner: ArrayRef,
+ field: FieldRef,
+}
+
+impl TypedArrayRef {
+ pub fn inner(&self) -> &ArrayRef {
+ &self.inner
+ }
+
+ pub fn into_inner(self) -> ArrayRef {
+ self.inner
+ }
+
+ pub fn field(&self) -> &FieldRef {
+ &self.field
+ }
+
+ // note: these methods below make me want to impl Array for
TypedArrayRef...
+ pub fn slice(&self, offset: usize, length: usize) -> Self {
+ let Self { inner, field } = self;
+
+ Self {
+ inner: inner.slice(offset, length),
+ field: Arc::clone(field),
+ }
+ }
+
+ pub fn is_valid(&self, index: usize) -> bool {
+ self.inner.is_valid(index)
+ }
Review Comment:
This definitely solves the problem of writing APIs that need to propgagate
extension metadata without constantly pairing a FieldRef. It may be worth
starting with the internal struct and the methods like you have here and moving
to a trait when there's a case that arises elsewhere that also needs that
concept? (I'm not very good at predicting where things should go inside the
arrow-rs crates)
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