fix: prevent duplicate alias collision with user-provided __datafusion_extracted names (#20432)

datafusion/common/src/alias.rs

@@ -37,6 +37,16 @@ impl AliasGenerator {
         Self::default()
     }
 
+    /// Advance the counter to at least `min_id`, ensuring future aliases
+    /// won't collide with already-existing ones.
+    ///
+    /// For example, if the query already contains an alias `alias_42`, then calling
+    /// `update_min_id(42)` will ensure that future aliases generated by this
+    /// [`AliasGenerator`] will start from `alias_43`.
+    pub fn update_min_id(&self, min_id: usize) {
+        self.next_id.fetch_max(min_id + 1, Ordering::Relaxed);
+    }
+
     /// Return a unique alias with the provided prefix
     pub fn next(&self, prefix: &str) -> String {
         let id = self.next_id.fetch_add(1, Ordering::Relaxed);