avoid extra allocation by mutating the var

Author: nikhilsinhaparseable

src/event/format/json.rs

@@ -268,9 +268,9 @@ fn rename_json_keys(values: Vec<Value>) -> Vec<Value> {
             if let Value::Object(map) = value {
                 let new_map: serde_json::Map<String, Value> = map
                     .into_iter()
-                    .map(|(key, val)| {
-                        let new_key = super::normalize_field_name(&key);
-                        (new_key, val)
+                    .map(|(mut key, val)| {
+                        super::normalize_field_name(&mut key);
+                        (key, val)
                     })
                     .collect();
                 Value::Object(new_map)
@@ -292,7 +292,8 @@ fn fields_mismatch(
             continue;
         }
         // Normalize field name to match schema transformation
-        let lookup_name = super::normalize_field_name(name);
+        let mut lookup_name = name.to_string();
+        super::normalize_field_name(&mut lookup_name);
         let Some(field) = get_field(schema, &lookup_name) else {
             return true;
         };

src/event/format/mod.rs

@@ -60,11 +60,9 @@ type EventSchema = Vec<Arc<Field>>;
 /// Normalizes a field name by replacing leading '@' with '_'.
 /// Fields starting with '@' are renamed to start with '_'.
 #[inline]
-pub fn normalize_field_name(name: &str) -> String {
+pub fn normalize_field_name(name: &mut String) {
     if let Some(stripped) = name.strip_prefix('@') {
-        format!("_{}", stripped)
-    } else {
-        name.to_string()
+        *name = format!("_{}", stripped);
     }
 }
 
@@ -347,7 +345,8 @@ pub fn override_data_type(
         .iter()
         .map(|field| {
             // Normalize field names - replace '@' prefix with '_'
-            let field_name = normalize_field_name(field.name());
+            let mut field_name = field.name().to_string();
+            normalize_field_name(&mut field_name);
             match (schema_version, map.get(field.name())) {
                 // in V1 for new fields in json named "time"/"date" or such and having inferred
                 // type string, that can be parsed as timestamp, use the timestamp type.