scovich commented on code in PR #9295:
URL: https://github.com/apache/arrow-rs/pull/9295#discussion_r2748723938
##########
arrow-array/src/array/mod.rs:
##########
@@ -350,12 +413,19 @@ pub unsafe trait Array: std::fmt::Debug + Send + Sync {
/// A reference-counted reference to a generic `Array`
pub type ArrayRef = Arc<dyn Array>;
-/// Ergonomics: Allow use of an ArrayRef as an `&dyn Array`
+/// Ergonomics: Allow use of an ArrayRef as an `&dyn Array`.
+/// Use [`Array::as_array_ref_opt()`] to recover the original [`ArrayRef`] and
+/// [`downcast_array_ref()`] to downcast to an Arc of some concrete array type.
unsafe impl Array for ArrayRef {
fn as_any(&self) -> &dyn Any {
self.as_ref().as_any()
}
+ fn as_array_ref_opt(&self) -> Option<ArrayRef> {
+ // Recursively unwrap nested Arcs to find the deepest one
+ Some(innermost_array_ref(Cow::Borrowed(self)))
Review Comment:
I tried removing `impl Array for Arc<dyn Array>` and the biggest problem is
that `Scalar<ArrayRef>` stops working. It's not immediately clear whether/how
to fix that. In particular, there's no obvious replacement for
`Scalar::new(new_null_array(...))`.
Other smaller messes include:
* Quite a few call sites that call `Arc::new(<expression returning
ArrayRef>) as ArrayRef` (there's that wrapping!)
* A surprising number of calls to `<ArrayRef as Array>::shrink_to_fit()`
(fake-mutable, no-op)
* Lots of calls to `<ArrayRef as Array>::into_data()` (fake-mutable,
equivalent to `Array::to_data`)
* A lot of code that has an `ArrayRef` or `&ArrayRef`, and which lacks the
necessary `.as_ref()` call. Mostly unit tests.
* Missing `impl Datum for ArrayRef`
Just getting arrow-rs to compile without it was an impressive amount of
churn:
```
82 files changed, 883 insertions(+), 732 deletions(-)
```
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