alamb commented on code in PR #22559:
URL: https://github.com/apache/datafusion/pull/22559#discussion_r3312514274
##########
datafusion/physical-plan/src/execution_plan.rs:
##########
@@ -115,6 +115,26 @@ pub trait ExecutionPlan: Any + Debug + DisplayAs + Send +
Sync {
}
}
+ /// Returns the plan that provides this plan's public
+ /// [`ExecutionPlan`] downcast identity.
+ ///
+ /// This hook is for wrapper nodes that delegate their public downcast
+ /// identity to another plan while adding cross-cutting behavior such as
+ /// instrumentation. The default implementation returns `None`, meaning
this
+ /// plan's concrete type is used for type introspection.
+ ///
+ /// The `is` and `downcast_ref` helpers follow the returned delegate
instead
Review Comment:
It might be good to add a specific example here (like a wrapper node that
wants to observe changes but still be treated as the underlying node when
DataFusion checks for patterns using `downcast` 🤔
##########
datafusion/physical-plan/src/execution_plan.rs:
##########
@@ -718,20 +738,32 @@ pub trait ExecutionPlan: Any + Debug + DisplayAs + Send +
Sync {
impl dyn ExecutionPlan {
/// Returns `true` if the plan is of type `T`.
///
+ /// If this plan provides a [`ExecutionPlan::downcast_delegate`], delegates
+ /// to it.
+ ///
/// Prefer this over `downcast_ref::<T>().is_some()`. Works correctly when
/// called on `Arc<dyn ExecutionPlan>` via auto-deref.
pub fn is<T: ExecutionPlan>(&self) -> bool {
- (self as &dyn Any).is::<T>()
+ match self.downcast_delegate() {
+ Some(delegate) => delegate.is::<T>(),
+ None => (self as &dyn Any).is::<T>(),
+ }
Review Comment:
Should we revert the hew `:Any` instead? I think it was just supposed to be
a cleanup but we didn't realize it would have downstream impacts 🤔
##########
datafusion/physical-plan/src/execution_plan.rs:
##########
@@ -718,20 +738,32 @@ pub trait ExecutionPlan: Any + Debug + DisplayAs + Send +
Sync {
impl dyn ExecutionPlan {
/// Returns `true` if the plan is of type `T`.
///
+ /// If this plan provides a [`ExecutionPlan::downcast_delegate`], delegates
+ /// to it.
+ ///
/// Prefer this over `downcast_ref::<T>().is_some()`. Works correctly when
/// called on `Arc<dyn ExecutionPlan>` via auto-deref.
pub fn is<T: ExecutionPlan>(&self) -> bool {
- (self as &dyn Any).is::<T>()
+ match self.downcast_delegate() {
+ Some(delegate) => delegate.is::<T>(),
+ None => (self as &dyn Any).is::<T>(),
+ }
Review Comment:
Also I wonder if there is some way to avoid using `as_any` / delegating
logic at all ... But to do that we would have to remove all uses of `as_any` /
`downcasting` I suspect
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