eliaperantoni commented on code in PR #14439:
URL: https://github.com/apache/datafusion/pull/14439#discussion_r1943778591
##########
datafusion/common/src/error.rs:
##########
@@ -540,6 +570,37 @@ impl DataFusionError {
DiagnosticsIterator { head: self }.next()
}
+
+ /// Sometimes DataFusion is able to collect multiple errors in a SQL query
+ /// before terminating, e.g. across different expressions in a SELECT
+ /// statements or different sides of a UNION. This method returns an
+ /// iterator over all the errors in the collection.
+ ///
+ /// For this to work, the top-level error must be a
+ /// `DataFusionError::Collection`, not something that contains it.
+ pub fn iter(&self) -> impl Iterator<Item = &DataFusionError> {
+ struct ErrorIterator<'a> {
+ queue: VecDeque<&'a DataFusionError>,
+ }
+
+ impl<'a> Iterator for ErrorIterator<'a> {
+ type Item = &'a DataFusionError;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ loop {
+ let popped = self.queue.pop_front()?;
+ match popped {
+ DataFusionError::Collection(errs) =>
self.queue.extend(errs),
+ _ => return Some(popped),
+ }
+ }
+ }
+ }
+
+ let mut queue = VecDeque::new();
+ queue.push_back(self);
+ ErrorIterator { queue }
+ }
Review Comment:
> That doesn't handle recursive Collections but I think that is ok
But then in a query like:
```sql
SELECT
bad,
bad
UNION
SELECT
bad
```
You would get one `DataFusionError::Collection` and one
`DataFusionError::Plan` whereas you could've gotten three
`DataFusionError::Plan`. I think that's worth having this `iter` that's
slightly more complicated.
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