Better comments

src/Databases/DDLDependencyVisitor.h

@@ -14,6 +14,8 @@ using TableNamesSet = std::unordered_set<QualifiedTableName>;
 /// For example, a column default expression can use dictGet() and thus reference a dictionary.
 /// Does not validate AST, works a best-effort way.
 TableNamesSet getDependenciesFromCreateQuery(const ContextPtr & global_context, const QualifiedTableName & table_name, const ASTPtr & ast, const String & current_database);
+
+/// Returns a list of all tables explicitly referenced in the select query specified as a dictionary source.
 TableNamesSet getDependenciesFromDictionaryNestedSelectQuery(const ContextPtr & global_context, const QualifiedTableName & table_name, const ASTPtr & ast, const String & select_query, const String & current_database);
 
 }

src/Databases/DDLLoadingDependencyVisitor.cpp

@@ -123,6 +123,7 @@ void DDLLoadingDependencyVisitor::visit(const ASTFunctionWithKeyValueArguments &
     else
     {
         /// We don't have a table name, we have a select query instead that will be executed during dictionary loading.
+        /// We need to find all tables used in this select query and add them to dependencies.
         auto select_query_dependencies = getDependenciesFromDictionaryNestedSelectQuery(data.global_context, data.table_name, data.create_query, info->query, data.default_database);
         data.dependencies.merge(select_query_dependencies);
     }