alamb commented on code in PR #4992:
URL: https://github.com/apache/arrow-datafusion/pull/4992#discussion_r1081668860
##########
datafusion/common/src/error.rs:
##########
@@ -359,84 +380,49 @@ impl DataFusionError {
///
/// This may be the same as `self`.
pub fn find_root(&self) -> &Self {
- // Note: This is a non-recursive algorithm so we do not run out of
stack space, even for long error chains. The
- // algorithm will always terminate because all steps access the
next error through "converging" ownership,
- // i.e. there can be a fan-in by multiple parents (e.g. via
`Arc`), but never a fan-out by multiple
- // children (e.g. via `Weak` or interior mutability via `Mutex`).
-
- // last error in the chain that was a DataFusionError
- let mut checkpoint: &Self = self;
-
- // current non-DataFusion error
- let mut other_e: Option<OtherErr<'_>> = None;
-
- loop {
- // do we have another error type to explore?
- if let Some(inner) = other_e {
- // `other_e` is now bound to `inner`, so we can clear this path
- other_e = None;
-
- match inner {
- OtherErr::Arrow(inner) => {
- if let ArrowError::ExternalError(inner) = inner {
- other_e = Some(OtherErr::Dyn(inner.as_ref()));
- continue;
- }
- }
- OtherErr::Dyn(inner) => {
- if let Some(inner) = inner.downcast_ref::<Self>() {
- checkpoint = inner;
- continue;
- }
-
- if let Some(inner) =
inner.downcast_ref::<ArrowError>() {
- other_e = Some(OtherErr::Arrow(inner));
- continue;
- }
-
- // some errors are wrapped into `Arc`s to share them
with multiple receivers
- if let Some(inner) = inner.downcast_ref::<Arc<Self>>()
{
- checkpoint = inner.as_ref();
- continue;
- }
-
- if let Some(inner) =
inner.downcast_ref::<Arc<ArrowError>>() {
- other_e = Some(OtherErr::Arrow(inner.as_ref()));
- continue;
- }
- }
- }
-
- // dead end?
- break;
- }
-
- // traverse context chain
- if let Self::Context(_msg, inner) = checkpoint {
- checkpoint = inner;
- continue;
+ // Note: This is a non-recursive algorithm so we do not run
+ // out of stack space, even for long error chains.
+
+ let mut last_datafusion_error = self;
+ let mut root_error: &dyn Error = self;
+ while let Some(source) = find_source(root_error) {
Review Comment:
I am quite pleased with how this works (and it will work for other
intervening wrapping error types if they implement `source()` as well)
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