kosiew commented on code in PR #23651:
URL: https://github.com/apache/datafusion/pull/23651#discussion_r3683436190


##########
datafusion/physical-plan/src/statistics.rs:
##########
@@ -182,35 +255,254 @@ impl StatisticsContext {
             requests.len(),
             children.len()
         );
-        let child_stats = children
+        children
             .iter()
             .zip(requests)
-            .map(|(child, directive)| match directive {
-                ChildStats::At(p) => {
-                    self.compute(child.as_ref(), 
&StatisticsArgs::new().with_partition(p))
-                }
+            .enumerate()
+            .map(|(i, (child, directive))| match directive {
+                ChildStats::At(p) => self
+                    .compute_base(child.as_ref(), 
&StatisticsArgs::new().with_partition(*p))
+                    .map_err(|e| {
+                        e.context(format!(
+                            "computing statistics for child {i} ({}) of {} at 
partition {p:?}",
+                            child.name(),
+                            plan.name()
+                        ))
+                    }),
                 ChildStats::Skip => {
                     
Ok(Arc::new(Statistics::new_unknown(child.schema().as_ref())))
                 }
             })
-            .collect::<Result<Vec<_>>>()?;
+            .collect()
+    }
+
+    /// Runs the provider chain, returning the first `Computed` result's core
+    /// statistics (and recording its extensions), or `None` if the chain is 
empty
+    /// or all delegate. A partition-blind provider applies only to overall 
stats
+    /// (its default `compute_statistics_with_args` delegates per partition).
+    ///
+    /// Each provider's child statistics come from its own
+    /// 
[`child_stats_requests`](crate::operator_statistics::StatisticsProvider::child_stats_requests)
+    /// and are memoized, so a walk with no providers pays nothing.
+    fn try_provider_stats(
+        &self,
+        plan: &dyn ExecutionPlan,
+        children: &[&Arc<dyn ExecutionPlan>],
+        args: &StatisticsArgs,
+    ) -> Result<Option<Arc<Statistics>>> {
+        let providers = self.registry.providers();
+        if providers.is_empty() {
+            return Ok(None);
+        }
+        let partition = args.partition();
+        for provider in providers {
+            if !provider.matches(plan) {
+                continue;

Review Comment:
   I like the delegate-chain fix, but I think we're now skipping too much.
   
   At the moment, every `resolve_children(...)` error falls into the same 
`continue` path. That means provider contract violations and other hard 
failures are treated the same as delegation failures, which can silently 
disable provider behavior and make bugs much harder to spot.
   
   Could we narrow the classification here so that only delegation-related 
failures are skipped? I'd keep the current eager resolution model, but continue 
to fail fast for provider contract violations, especially request-length 
mismatches, and other hard errors.



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