feat: RegisterTable support for InMemoryCatalog

Author: shuxu.li

src/iceberg/catalog.h

@@ -166,8 +166,7 @@ class ICEBERG_EXPORT Catalog {
   /// \param identifier a table identifier
   /// \return instance of Table implementation referred to by identifier or
   /// ErrorKind::kNoSuchTable if the table does not exist
-  virtual Result<std::shared_ptr<Table>> LoadTable(
-      const TableIdentifier& identifier) const = 0;
+  virtual Result<std::shared_ptr<Table>> LoadTable(const TableIdentifier& identifier) = 0;
 
   /// \brief Register a table with the catalog if it does not exist
   ///

src/iceberg/catalog/in_memory_catalog.cc

@@ -409,22 +409,24 @@ Status InMemoryCatalog::DropTable(const TableIdentifier& identifier, bool purge)
 }
 
 Result<std::shared_ptr<Table>> InMemoryCatalog::LoadTable(
-    const TableIdentifier& identifier) const {
+    const TableIdentifier& identifier) {
   if (!file_io_) [[unlikely]] {
     return NotSupported("file_io is not set for catalog {}", catalog_name_);
   }
 
-  std::unique_lock lock(mutex_);
-  auto metadata_location = root_namespace_->GetTableMetadataLocation(identifier);
-  ICEBERG_RETURN_UNEXPECTED(metadata_location);
+  Result<std::string> metadata_location;
+  {
+    std::unique_lock lock(mutex_);
+    metadata_location = root_namespace_->GetTableMetadataLocation(identifier);
+    ICEBERG_RETURN_UNEXPECTED(metadata_location);
+  }
 
   auto metadata = TableMetadataUtil::Read(*file_io_, metadata_location.value());
   ICEBERG_RETURN_UNEXPECTED(metadata);
 
-  return std::make_shared<Table>(
-      identifier, std::move(metadata.value()), metadata_location.value(), file_io_,
-      std::static_pointer_cast<Catalog>(
-          std::const_pointer_cast<InMemoryCatalog>(shared_from_this())));
+  return std::make_shared<Table>(identifier, std::move(metadata.value()),
+                                 metadata_location.value(), file_io_,
+                                 std::static_pointer_cast<Catalog>(shared_from_this()));
 }
 
 Result<std::shared_ptr<Table>> InMemoryCatalog::RegisterTable(

src/iceberg/catalog/in_memory_catalog.h

@@ -84,8 +84,7 @@ class ICEBERG_EXPORT InMemoryCatalog
 
   Status DropTable(const TableIdentifier& identifier, bool purge) override;
 
-  Result<std::shared_ptr<Table>> LoadTable(
-      const TableIdentifier& identifier) const override;
+  Result<std::shared_ptr<Table>> LoadTable(const TableIdentifier& identifier) override;
 
   Result<std::shared_ptr<Table>> RegisterTable(
       const TableIdentifier& identifier,

test/in_memory_catalog_test.cc

@@ -51,6 +51,7 @@ class InMemoryCatalogTest : public ::testing::Test {
     std::filesystem::remove_all(temp_filepath_, ec);
   }
 
+  // Used to generate a unique temporary metadata path for the test table
   std::string temp_filepath_;
   std::shared_ptr<FileIO> file_io_;
   std::shared_ptr<InMemoryCatalog> catalog_;