rename once_flag in schema

Author: nullccxsy

src/iceberg/schema.cc

@@ -90,13 +90,13 @@ Result<std::optional<std::reference_wrapper<const SchemaField>>> Schema::FindFie
     std::string_view name, bool case_sensitive) const {
   if (case_sensitive) {
     ICEBERG_RETURN_UNEXPECTED(
-        LazyInitWithCallOnce(name_flag_, [this]() { return InitNameToIdMap(); }));
+        LazyInitWithCallOnce(name_to_id_flag_, [this]() { return InitNameToIdMap(); }));
     auto it = name_to_id_.find(name);
     if (it == name_to_id_.end()) return std::nullopt;
     return FindFieldById(it->second);
   }
   ICEBERG_RETURN_UNEXPECTED(LazyInitWithCallOnce(
-      lowercase_name_flag_, [this]() { return InitLowerCaseNameToIdMap(); }));
+      lowercase_name_to_id_flag_, [this]() { return InitLowerCaseNameToIdMap(); }));
   auto it = lowercase_name_to_id_.find(StringUtils::ToLower(name));
   if (it == lowercase_name_to_id_.end()) return std::nullopt;
   return FindFieldById(it->second);
@@ -136,7 +136,7 @@ Status Schema::InitLowerCaseNameToIdMap() const {
 Result<std::optional<std::reference_wrapper<const SchemaField>>> Schema::FindFieldById(
     int32_t field_id) const {
   ICEBERG_RETURN_UNEXPECTED(
-      LazyInitWithCallOnce(id_flag_, [this]() { return InitIdToFieldMap(); }));
+      LazyInitWithCallOnce(id_to_field_flag_, [this]() { return InitIdToFieldMap(); }));
   auto it = id_to_field_.find(field_id);
   if (it == id_to_field_.end()) {
     return std::nullopt;

src/iceberg/schema.h

@@ -83,7 +83,7 @@ class ICEBERG_EXPORT Schema : public StructType {
   Status InitNameToIdMap() const;
   Status InitLowerCaseNameToIdMap() const;
 
-  std::optional<int32_t> schema_id_;
+  const std::optional<int32_t> schema_id_;
   /// Mapping from field id to field.
   mutable std::unordered_map<int32_t, std::reference_wrapper<const SchemaField>>
       id_to_field_;
@@ -94,9 +94,9 @@ class ICEBERG_EXPORT Schema : public StructType {
   mutable std::unordered_map<std::string, int32_t, StringHash, std::equal_to<>>
       lowercase_name_to_id_;
 
-  mutable std::once_flag id_flag_;
-  mutable std::once_flag name_flag_;
-  mutable std::once_flag lowercase_name_flag_;
+  mutable std::once_flag id_to_field_flag_;
+  mutable std::once_flag name_to_id_flag_;
+  mutable std::once_flag lowercase_name_to_id_flag_;
 };
 
 }  // namespace iceberg