[GitHub] [arrow-rs] tustvold commented on a diff in pull request #3148: refactor: convert `Field::metadata` to `HashMap`

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

tustvold commented on code in PR #3148:
URL: https://github.com/apache/arrow-rs/pull/3148#discussion_r1028204159


##########
arrow-schema/src/field.rs:
##########
@@ -68,9 +68,33 @@ impl Ord for Field {
     fn cmp(&self, other: &Self) -> Ordering {
         self.name
             .cmp(other.name())
-            .then(self.data_type.cmp(other.data_type()))
-            .then(self.nullable.cmp(&other.nullable))
-            .then(self.metadata.cmp(&other.metadata))
+            .then_with(|| self.data_type.cmp(other.data_type()))
+            .then_with(|| self.nullable.cmp(&other.nullable))
+            .then_with(|| {
+                // ensure deterministic key order
+                let mut keys: Vec<&String> =
+                    self.metadata.keys().chain(other.metadata.keys()).collect();
+                keys.sort();
+                for k in keys {
+                    match (self.metadata.get(k), other.metadata.get(k)) {
+                        (None, None) => {}
+                        (Some(_), None) => {
+                            return Ordering::Greater;

Review Comment:
   Is this the correct way round?



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