[GitHub] [arrow-datafusion] yjshen commented on a diff in pull request #2384: Allow CTEs to be referenced from subquery expressions

[GitBox <gi...@apache.org>]

yjshen commented on code in PR #2384:
URL: https://github.com/apache/arrow-datafusion/pull/2384#discussion_r862408152


##########
datafusion/common/src/dfschema.rs:
##########
@@ -133,18 +133,22 @@ impl DFSchema {
     /// Modify this schema by appending the fields from the supplied schema, ignoring any
     /// duplicate fields.
     pub fn merge(&mut self, other_schema: &DFSchema) {
-        for field in other_schema.fields() {
-            // skip duplicate columns
-            let duplicated_field = match field.qualifier() {
-                Some(q) => self.field_with_name(Some(q.as_str()), field.name()).is_ok(),
-                // for unqualifed columns, check as unqualified name
-                None => self.field_with_unqualified_name(field.name()).is_ok(),
-            };
-            if !duplicated_field {
-                self.fields.push(field.clone());
+        if !other_schema.fields.is_empty() {

Review Comment:
   An earlier return might be cleaner?



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