Method iter

datafusion/common/src/error.rs:650–672

Return an iterator over this [`DataFusionError`] and any other [`DataFusionError`]s in a [`DataFusionError::Collection`]. 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-

(&self)

    /// 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 }
    }
}

/// A builder for [`DataFusionError`]