use const ref for current

Author: wgtmac

src/iceberg/table_metadata.cc

@@ -796,6 +796,6 @@ const std::vector<std::unique_ptr<TableUpdate>>& TableMetadataBuilder::changes()
 
 const TableMetadata* TableMetadataBuilder::base() const { return impl_->base; }
 
-const TableMetadata* TableMetadataBuilder::current() const { return &impl_->metadata; }
+const TableMetadata& TableMetadataBuilder::current() const { return impl_->metadata; }
 
 }  // namespace iceberg

src/iceberg/table_metadata.h

@@ -426,7 +426,7 @@ class ICEBERG_EXPORT TableMetadataBuilder : public ErrorCollector {
   const TableMetadata* base() const;
 
   /// \brief Returns the current metadata with staged changes applied
-  const TableMetadata* current() const;
+  const TableMetadata& current() const;
 
   /// \brief Destructor
   ~TableMetadataBuilder() override;

src/iceberg/transaction.cc

@@ -49,7 +49,7 @@ Result<std::shared_ptr<Transaction>> Transaction::Make(std::shared_ptr<Table> ta
 
 const TableMetadata* Transaction::base() const { return metadata_builder_->base(); }
 
-const TableMetadata* Transaction::current() const { return metadata_builder_->current(); }
+const TableMetadata& Transaction::current() const { return metadata_builder_->current(); }
 
 Status Transaction::AddUpdate(const std::shared_ptr<PendingUpdate>& update) {
   if (!last_update_committed_) {

src/iceberg/transaction.h

@@ -47,7 +47,7 @@ class ICEBERG_EXPORT Transaction : public std::enable_shared_from_this<Transacti
   const TableMetadata* base() const;
 
   /// \brief Return the current metadata with staged changes applied
-  const TableMetadata* current() const;
+  const TableMetadata& current() const;
 
   /// \brief Apply the pending changes from all actions and commit.
   ///

src/iceberg/update/update_properties.cc

@@ -78,11 +78,6 @@ UpdateProperties& UpdateProperties::Remove(const std::string& key) {
 Result<PendingUpdate::ApplyResult> UpdateProperties::Apply() {
   ICEBERG_RETURN_UNEXPECTED(CheckErrors());
 
-  const auto* base_metadata = transaction_->current();
-  if (!base_metadata) {
-    return InvalidArgument("Base table metadata is required to apply property updates");
-  }
-
   auto iter = updates_.find(TableProperties::kFormatVersion.key());
   if (iter != updates_.end()) {
     int parsed_version = 0;
@@ -105,7 +100,7 @@ Result<PendingUpdate::ApplyResult> UpdateProperties::Apply() {
     updates_.erase(iter);
   }
 
-  if (auto schema = base_metadata->Schema(); schema.has_value()) {
+  if (auto schema = transaction_->current().Schema(); schema.has_value()) {
     ICEBERG_RETURN_UNEXPECTED(
         MetricsConfig::VerifyReferencedColumns(updates_, *schema.value()));
   }