make explain output stable (#44)

src/rewrite/exploitation.rs

@@ -274,7 +274,10 @@ impl UserDefinedLogicalNodeCore for OneOf {
     }
 
     fn inputs(&self) -> Vec<&LogicalPlan> {
-        self.branches.iter().collect_vec()
+        self.branches
+            .iter()
+            .sorted_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal))
+            .collect_vec()
     }
 
     fn schema(&self) -> &datafusion_common::DFSchemaRef {