include/matador/sql/interface/parameter_binder.hpp

@@ -3,7 +3,7 @@
 
 #include "matador/utils/attribute_writer.hpp"
 
-namespace matador::sql {
+namespace matador::sql::interface {
 
 using parameter_binder = utils::attribute_writer;
 

include/matador/sql/interface/statement_impl.hpp

@@ -22,23 +22,23 @@ protected:
 public:
   virtual ~statement_impl() = default;
 
-  virtual utils::result<size_t, utils::error> execute(const parameter_binder& bindings) = 0;
-  virtual utils::result<std::unique_ptr<query_result_impl>, utils::error> fetch(const parameter_binder& bindings) = 0;
+  virtual utils::result<size_t, utils::error> execute(const interface::parameter_binder& bindings) = 0;
+  virtual utils::result<std::unique_ptr<query_result_impl>, utils::error> fetch(const interface::parameter_binder& bindings) = 0;
 
   template < class Type >
-  void bind_object(Type &obj, parameter_binder& bindings) {
+  void bind_object(Type &obj, interface::parameter_binder& bindings) {
     object_parameter_binder object_binder_;
     object_binder_.reset(start_index());
     object_binder_.bind(obj, bindings);
   }
 
   template < class Type >
-  void bind(const size_t pos, Type &val, parameter_binder& bindings) {
+  void bind(const size_t pos, Type &val, interface::parameter_binder& bindings) {
     utils::data_type_traits<Type>::bind_value(bindings, adjust_index(pos), val);
   }
 
-  void bind(size_t pos, const char *value, size_t size, parameter_binder& bindings) const;
-  void bind(size_t pos, std::string &val, size_t size, parameter_binder& bindings) const;
+  void bind(size_t pos, const char *value, size_t size, interface::parameter_binder& bindings) const;
+  void bind(size_t pos, std::string &val, size_t size, interface::parameter_binder& bindings) const;
 
   virtual void reset() = 0;
 

include/matador/sql/interface/statement_proxy.hpp

@@ -12,19 +12,19 @@ protected:
 public:
   virtual ~statement_proxy() = default;
 
-  virtual utils::result<size_t, utils::error> execute(parameter_binder& bindings) = 0;
-  virtual utils::result<std::unique_ptr<query_result_impl>, utils::error> fetch(parameter_binder& bindings) = 0;
+  virtual utils::result<size_t, utils::error> execute(interface::parameter_binder& bindings) = 0;
+  virtual utils::result<std::unique_ptr<query_result_impl>, utils::error> fetch(interface::parameter_binder& bindings) = 0;
 
   template<class Type>
-  void bind(const Type &obj, parameter_binder& bindings) {
+  void bind(const Type &obj, interface::parameter_binder& bindings) {
     statement_->bind_object(obj, bindings);
   }
   template<typename Type>
-  void bind(size_t pos, Type &value, parameter_binder& bindings) {
+  void bind(size_t pos, Type &value, interface::parameter_binder& bindings) {
     statement_->bind(pos, value, bindings);
   }
-  void bind(size_t pos, const char *value, size_t size, parameter_binder& bindings) const;
-  void bind(size_t pos, std::string &val, size_t size, parameter_binder& bindings) const;
+  void bind(size_t pos, const char *value, size_t size, interface::parameter_binder& bindings) const;
+  void bind(size_t pos, std::string &val, size_t size, interface::parameter_binder& bindings) const;
 
   void reset() const;
 

include/matador/sql/statement_cache.hpp

@@ -23,19 +23,6 @@ struct statement_accessed_event : statement_event {};
 struct statement_added_event : statement_event {};
 struct statement_evicted_event : statement_event {};
 
-struct statement_lock_failed_event : statement_event {
-  std::chrono::steady_clock::time_point lock_attempt_start;
-};
-
-struct statement_lock_acquired_event : statement_event {
-  std::chrono::steady_clock::time_point lock_attempt_start;
-  std::chrono::steady_clock::time_point lock_attempt_end;
-};
-
-struct statement_execution_event : statement_event {
-  std::chrono::steady_clock::time_point execution_start;
-  std::chrono::steady_clock::time_point execution_end;
-};
 
 struct statement_cache_config {
   size_t max_size;

include/matador/utils/message_bus.hpp

@@ -14,109 +14,60 @@
 #include <stdexcept>
 
 namespace matador::utils {
-class message_bus;
+class message_bus; // forward
 
-/**
- * @brief Represents a generic, type-safe message object used for communication.
- */
 class message {
 public:
-    /**
-     * @brief Default constructor for an empty message.
-     */
     message();
 
-    /**
-     * @brief Constructs an owning message from a value.
-     *
-     * @tparam MessageType The type of the message.
-     * @param msg The message to be stored. A copy is made.
-     */
-    template<typename MessageType>
-    explicit message(const MessageType& msg) {
-        auto strong = std::make_shared<MessageType>(msg);               // allocate
+    // Owning: copy into an owned shared_ptr (may allocate)
+    template<typename T>
+    explicit message(const T& value) {
+        auto strong = std::make_shared<T>(value);               // allocate
         owner_ = std::static_pointer_cast<void>(strong);       // share ownership as void*
         ptr_ = static_cast<const void*>(strong.get());
-        type_ = std::type_index(typeid(MessageType));
+        type_ = std::type_index(typeid(T));
     }
 
-    /**
-     * @brief Constructs a non-owning message from a reference.
-     *
-     * @tparam MessageType The type of the reference.
-     * @param msg A reference to the message data. The caller must ensure its lifetime during use.
-     * @return A non-owning message wrapping the reference.
-     */
-    template<typename MessageType>
-    static message from_ref(const MessageType& msg) {
+    // Non-owning: zero-copy reference to an existing object (no allocation)
+    // Caller must guarantee lifetime of `ref` for the usage duration.
+    template<typename T>
+    static message from_ref(const T& ref) {
         message m;
-        m.ptr_ = static_cast<const void*>(std::addressof(msg));
-        m.type_ = std::type_index(typeid(MessageType));
+        m.ptr_ = static_cast<const void*>(std::addressof(ref));
+        m.type_ = std::type_index(typeid(T));
         // owner_ remains null => non-owning
         return m;
     }
 
-    /**
-     * @brief Constructs an owning message from a shared pointer.
-     *
-     * @tparam MessageType The type of the object managed by the shared pointer.
-     * @param msg A shared pointer to the message.
-     * @return A message that shares ownership of the object.
-     */
-    template<typename MessageType>
-    static message from_shared(std::shared_ptr<MessageType> msg) {
+    // Owning from shared_ptr (no extra copy; shares ownership)
+    template<typename T>
+    static message from_shared(std::shared_ptr<T> sp) {
         message m;
-        m.owner_ = std::static_pointer_cast<void>(msg);
-        m.ptr_ = static_cast<const void*>(msg.get());
-        m.type_ = std::type_index(typeid(MessageType));
+        m.owner_ = std::static_pointer_cast<void>(sp);
+        m.ptr_ = static_cast<const void*>(sp.get());
+        m.type_ = std::type_index(typeid(T));
         return m;
     }
 
-    /**
-     * @brief Checks if the message is empty.
-     *
-     * @return True if the message is empty, false otherwise.
-     */
     [[nodiscard]] bool empty() const;
-
-    /**
-     * @brief Gets the type of the object stored in the message.
-     *
-     * @return The type of the stored object as a std::type_index.
-     */
     [[nodiscard]] std::type_index type() const;
 
-    /**
-     * @brief Checks if the stored object is of the specified type.
-     *
-     * @tparam MessageType The type to check.
-     * @return True if the object matches the type, false otherwise.
-     */
-    template<typename MessageType>
-    [[nodiscard]] bool is() const { return type_ == std::type_index(typeid(MessageType)); }
+    template<typename T>
+    [[nodiscard]] bool is() const { return type_ == std::type_index(typeid(T)); }
 
-    /**
-     * @brief Accesses the stored object as a typed reference.
-     *
-     * @tparam MessageType The expected type of the object.
-     * @return A constant reference to the stored object.
-     * @throws std::bad_cast if the type does not match.
-     * @throws std::runtime_error if the message is empty.
-     */
-    template<typename MessageType>
-    const MessageType& get() const {
-        if (!is<MessageType>()) throw std::bad_cast();
-        const void* p = raw_ptr();
+    // Access as typed reference. Works for both owning and non-owning.
+    // Throws std::bad_cast if type mismatch.
+    template<typename T>
+    const T& get() const {
+        if (!is<T>()) throw std::bad_cast();
+        const void* p = msg_ptr();
         if (!p) throw std::runtime_error("AnyMessage: empty pointer");
-        return *static_cast<const MessageType*>(p);
+        return *static_cast<const T*>(p);
     }
 
-    /**
-     * @brief Retrieves the raw pointer to the stored object.
-     *
-     * @return A const void* pointing to the stored object (may be non-owning).
-     */
-    [[nodiscard]] const void* raw_ptr() const;
+    // Return the raw const void* pointer to the stored object (may be non-owning)
+    [[nodiscard]] const void* msg_ptr() const;
 
 private:
     const void* ptr_;                 // non-owning raw pointer (if set)
@@ -124,46 +75,22 @@ private:
     std::type_index type_{typeid(void)};
 };
 
-/**
- * @brief Represents a subscription to a message_bus, providing RAII-style unsubscription.
- */
+// Forward declare Subscription so MessageBus can return it.
 class subscription {
 public:
-    /**
-     * @brief Default constructor for an empty subscription.
-     */
     subscription() = default;
-    /**
-     * @brief Constructs a subscription for a specific handler and message type.
-     *
-     * @param bus Pointer to the message bus managing the subscription.
-     * @param type The type_index of the message type.
-     * @param id The unique ID of the handler.
-     */
     subscription(message_bus* bus, std::type_index type, uint64_t id);
 
-    // Prohibit copying of subscription objects.
+    // Move-only (non-copyable)
     subscription(const subscription&) = delete;
     subscription& operator=(const subscription&) = delete;
-    // Allow move semantics for subscription objects.
     subscription(subscription&& other) noexcept;
     subscription& operator=(subscription&& other) noexcept;
 
-    /**
-     * @brief Destructor that ensures cleanup by unsubscribing from the bus.
-     */
     ~subscription();
 
-    /**
-     * @brief Unsubscribes the handler from the message bus.
-     */
     void unsubscribe();
 
-    /**
-     * @brief Checks if the subscription is still valid.
-     *
-     * @return True if the subscription is valid, false otherwise.
-     */
     [[nodiscard]] bool valid() const;
 
 private:
@@ -172,139 +99,90 @@ private:
     uint64_t id_ = 0;
 };
 
-/**
- * @brief A thread-safe message bus for runtime message publishing and subscription handling.
- */
+// === MessageBus: runtime-registered, thread-safe ===
 class message_bus {
 public:
-    using HandlerId = uint64_t; /**< Type alias for handler IDs. */
+    using HandlerId = uint64_t;
 
-    /**
-     * @brief Constructs a new message_bus object.
-     */
-    message_bus();
+    message_bus() : next_id_{1} {}
 
-    /**
-     * @brief Subscribes to messages of a specific type using a free function or lambda.
-     *
-     * @tparam MessageType The type of the message to subscribe to.
-     * @param handler The function to execute when a message of type T is published.
-     * @param filter An optional filter function to determine if the handler should be invoked.
-     * @return A subscription object to manage the handler's registration.
-     */
-    template<typename MessageType>
-    subscription subscribe(std::function<void(const MessageType&)> handler,
-                           std::function<bool(const MessageType&)> filter = nullptr)
+    // Subscribe with a free function or lambda
+    template<typename T>
+    subscription subscribe(std::function<void(const T&)> handler,
+                           std::function<bool(const T&)> filter = nullptr)
     {
         auto id = next_id_.fetch_add(1, std::memory_order_relaxed);
         std::unique_lock writeLock(mutex_);
 
-        auto &vec = handlers_[std::type_index(typeid(MessageType))];
+        auto &vec = handlers_[std::type_index(typeid(T))];
         Entry e;
         e.id = id;
         e.handler = [h = std::move(handler)](const void* p) {
-            h(*static_cast<const MessageType*>(p));
+            h(*static_cast<const T*>(p));
         };
         if (filter) {
             e.filter = [f = std::move(filter)](const void* p) -> bool {
-                return f(*static_cast<const MessageType*>(p));
+                return f(*static_cast<const T*>(p));
             };
         } else {
             e.filter = nullptr;
         }
         vec.emplace_back(std::move(e));
-        return {this, std::type_index(typeid(MessageType)), id};
+        return {this, std::type_index(typeid(T)), id};
     }
 
-    /**
-     * @brief Subscribes to messages using a class member function bound to an instance.
-     *
-     * @tparam MessageType The type of the message to subscribe to.
-     * @tparam CallerClass The class of the instance.
-     * @param instance A pointer to the instance.
-     * @param memberFn A pointer to the member function to execute.
-     * @param filter An optional filter function.
-     * @return A subscription object to manage the handler's registration.
-     */
-    template<typename MessageType, typename CallerClass>
-    subscription subscribe(CallerClass* instance, void (CallerClass::*memberFn)(const MessageType&),
-                           std::function<bool(const MessageType&)> filter = nullptr)
+    // Subscribe raw pointer instance; caller ensures lifetime
+    template<typename T, typename C>
+    subscription subscribe(C* instance, void (C::*memberFn)(const T&),
+                           std::function<bool(const T&)> filter = nullptr)
     {
-        auto fn = [instance, memberFn](const MessageType& m) { (instance->*memberFn)(m); };
-        return subscribe<MessageType>(std::function<void(const MessageType&)>(fn), std::move(filter));
+        auto fn = [instance, memberFn](const T& m) { (instance->*memberFn)(m); };
+        return subscribe<T>(std::function<void(const T&)>(fn), std::move(filter));
     }
 
-    /**
-     * @brief Subscribes to messages using a member function bound to a shared_ptr instance.
-     *
-     * @tparam MessageType The type of the message to subscribe to.
-     * @tparam CallerClass The class of the shared_ptr instance.
-     * @param instance A shared pointer to the instance.
-     * @param memberFn A pointer to the member function to execute.
-     * @param filter An optional filter function.
-     * @return A subscription object to manage the handler's registration.
-     */
-    template<typename MessageType, typename CallerClass>
-    subscription subscribe(std::shared_ptr<CallerClass> instance, void (CallerClass::*memberFn)(const MessageType&),
-                           std::function<bool(const MessageType&)> filter = nullptr)
+    // Subscribe shared_ptr instance (safe)
+    template<typename T, typename C>
+    subscription subscribe(std::shared_ptr<C> instance, void (C::*memberFn)(const T&),
+                           std::function<bool(const T&)> filter = nullptr)
     {
-        std::weak_ptr<CallerClass> w = instance;
-        auto handler = [w, memberFn](const MessageType& m) {
+        std::weak_ptr<C> w = instance;
+        auto handler = [w, memberFn](const T& m) {
             if (auto s = w.lock()) {
                 (s.get()->*memberFn)(m);
             }
         };
 
-        std::function<bool(const MessageType&)> local_filter = nullptr;
+        std::function<bool(const T&)> local_filter = nullptr;
         if (filter) {
-            local_filter = [w, filter = std::move(filter)](const MessageType& m) -> bool {
+            local_filter = [w, filter = std::move(filter)](const T& m) -> bool {
                 if (w.expired()) {
                     return false;
                 }
                 return filter(m);
             };
         }
-        return subscribe<MessageType>(std::move(handler), std::move(local_filter));
+        return subscribe<T>(std::move(handler), std::move(local_filter));
     }
 
-    /**
-     * @brief Unsubscribes a handler from the bus using its type and ID.
-     *
-     * @tparam MessageType The type of the message.
-     * @param id The unique handler ID to unsubscribe.
-     */
-    template<typename MessageType>
+    // Unsubscribe by type-specific id (RAII calls this)
+    template<typename T>
     void unsubscribe(const HandlerId id) {
-        unsubscribe(std::type_index(typeid(MessageType)), id);
+        unsubscribe(std::type_index(typeid(T)), id);
     }
 
-    /**
-     * @brief Unsubscribes a handler by its type index and ID.
-     *
-     * @param type The type_index of the message type.
-     * @param id The unique handler ID to unsubscribe.
-     */
+    // Unsubscribe by explicit type_index and id
     void unsubscribe(std::type_index type, HandlerId id);
 
-    /**
-     * @brief Unsubscribes a handler by its unique ID, regardless of type.
-     *
-     * @param id The unique handler ID to unsubscribe.
-     */
+    // Unsubscribe by id regardless of type (O(#types) scan)
     void unsubscribe(HandlerId id);
 
-    /**
-     * @brief Publishes a message of a specific type.
-     *
-     * @tparam MessageType The type of the message to publish.
-     * @param msg The message to publish.
-     */
-    template<typename MessageType>
-    void publish(const MessageType& msg) const {
+    // Publish a typed message (fast)
+    template<typename T>
+    void publish(const T& msg) const {
         std::vector<Entry> snapshot;
         {
             std::shared_lock readLock(mutex_);
-            const auto it = handlers_.find(std::type_index(typeid(MessageType)));
+            const auto it = handlers_.find(std::type_index(typeid(T)));
             if (it == handlers_.end()) {
                 return;
             }
@@ -315,11 +193,7 @@ public:
         }
     }
 
-    /**
-     * @brief Publishes a generic message object.
-     *
-     * @param msg The message to publish.
-     */
+    // Publish using AnyMessage (zero-copy if AnyMessage is non-owning)
     void publish(const message& msg) const;
 
 private:
@@ -336,6 +210,7 @@ private:
     std::atomic<HandlerId> next_id_;
 };
 
+// RAII unsubscribe implementation
 inline void subscription::unsubscribe() {
     if (bus_) {
         bus_->unsubscribe(type_, id_);

source/core/utils/message_bus.cpp

@@ -14,7 +14,7 @@ std::type_index message::type() const {
   return type_;
 }
 
-const void * message::raw_ptr() const {
+const void * message::msg_ptr() const {
   return owner_ ? owner_.get() : ptr_;
 }
 
@@ -49,9 +49,6 @@ bool subscription::valid() const {
   return bus_ != nullptr;
 }
 
-message_bus::message_bus()
-: next_id_{1} {}
-
 void message_bus::unsubscribe(const std::type_index type, HandlerId id) {
   std::unique_lock writeLock(mutex_);
   const auto it = handlers_.find(type);
@@ -92,7 +89,7 @@ void message_bus::publish(const message &msg) const {
     }
     snapshot = it->second;
   }
-  const void* p = msg.raw_ptr();
+  const void* p = msg.msg_ptr();
   for (const auto &e : snapshot) {
     if (!e.filter || e.filter(p)) e.handler(p);
   }

source/orm/sql/connection.cpp

@@ -19,10 +19,10 @@ public:
   explicit connection_statement_proxy(std::unique_ptr<statement_impl>&& stmt)
   : statement_proxy(std::move(stmt)) {}
 
-  utils::result<size_t, utils::error> execute(parameter_binder& bindings) override {
+  utils::result<size_t, utils::error> execute(interface::parameter_binder& bindings) override {
     return statement_->execute(bindings);
   }
-  utils::result<std::unique_ptr<query_result_impl>, utils::error> fetch(parameter_binder& bindings) override {
+  utils::result<std::unique_ptr<query_result_impl>, utils::error> fetch(interface::parameter_binder& bindings) override {
     return statement_->fetch(bindings);
   }
 };

source/orm/sql/interface/statement_impl.cpp

@@ -6,11 +6,11 @@ statement_impl::statement_impl(query_context query)
 : query_(std::move(query))
 {}
 
-void statement_impl::bind(const size_t pos, const char *value, const size_t size, parameter_binder& bindings) const {
+void statement_impl::bind(const size_t pos, const char *value, const size_t size, interface::parameter_binder& bindings) const {
   utils::data_type_traits<const char*>::bind_value(bindings, adjust_index(pos), value, size);
 }
 
-void statement_impl::bind(const size_t pos, std::string &val, const size_t size, parameter_binder& bindings) const {
+void statement_impl::bind(const size_t pos, std::string &val, const size_t size, interface::parameter_binder& bindings) const {
   utils::data_type_traits<std::string>::bind_value(bindings, adjust_index(pos), val, size);
 }
 

source/orm/sql/interface/statement_proxy.cpp

@@ -4,10 +4,10 @@ namespace matador::sql {
 statement_proxy::statement_proxy(std::unique_ptr<statement_impl>&& stmt)
 : statement_(std::move(stmt)){}
 
-void statement_proxy::bind(const size_t pos, const char* value, const size_t size, parameter_binder& bindings) const {
+void statement_proxy::bind(const size_t pos, const char* value, const size_t size, interface::parameter_binder& bindings) const {
   statement_->bind(pos, value, size, bindings);
 }
-void statement_proxy::bind(const size_t pos, std::string& val, const size_t size, parameter_binder& bindings) const {
+void statement_proxy::bind(const size_t pos, std::string& val, const size_t size, interface::parameter_binder& bindings) const {
   statement_->bind(pos, val, size, bindings);
 }
 

source/orm/sql/statement_cache.cpp

@@ -24,26 +24,24 @@ public:
     size_t lock_attempts{0};
   };
 
-  statement_cache_proxy(utils::message_bus &bus, std::unique_ptr<statement_impl>&& stmt, connection_pool &pool, const size_t connection_id)
+  explicit statement_cache_proxy(std::unique_ptr<statement_impl>&& stmt, connection_pool &pool, const size_t connection_id)
   : statement_proxy(std::move(stmt))
   , pool_(pool)
-  , connection_id_(connection_id)
-  , bus_(bus) {}
+  , connection_id_(connection_id) {}
 
-  utils::result<size_t, utils::error> execute(parameter_binder& bindings) override {
+  utils::result<size_t, utils::error> execute(interface::parameter_binder& bindings) override {
     execution_metrics metrics{std::chrono::steady_clock::now()};
 
     auto result = try_with_retry([this, &bindings, &metrics]() -> utils::result<size_t, utils::error> {
       if (!try_lock()) {
         ++metrics.lock_attempts;
-        bus_.publish<statement_lock_failed_event>({sql(), std::chrono::steady_clock::now(), metrics.lock_attempt_start});
         return utils::failure(utils::error{
           error_code::STATEMENT_LOCKED,
           "Failed to execute statement because it is already in use"
         });
       }
       metrics.lock_acquired = std::chrono::steady_clock::now();
-      bus_.publish<statement_lock_acquired_event>({sql(), std::chrono::steady_clock::now(), metrics.lock_attempt_start, metrics.lock_acquired});
+      // publish
 
       auto guard = statement_guard(*this);
       if (const auto conn = pool_.acquire(connection_id_); !conn.valid()) {
@@ -57,15 +55,14 @@ public:
       auto execution_result = statement_->execute(bindings);
       metrics.execution_end = std::chrono::steady_clock::now();
 
-      bus_.publish<statement_execution_event>({sql(), std::chrono::steady_clock::now(), metrics.execution_start, metrics.execution_end});
-
+      // publish
       return execution_result;
     });
 
     return result;
   }
 
-  utils::result<std::unique_ptr<query_result_impl>, utils::error> fetch(parameter_binder& bindings) override {
+  utils::result<std::unique_ptr<query_result_impl>, utils::error> fetch(interface::parameter_binder& bindings) override {
     execution_metrics metrics{std::chrono::steady_clock::now()};
 
     auto result = try_with_retry([this, &bindings, &metrics]() -> utils::result<std::unique_ptr<query_result_impl>, utils::error> {
@@ -107,7 +104,7 @@ protected:
 
       if (attempt + 1 < config_.max_attempts) {
         std::this_thread::sleep_for(current_wait);
-        current_wait = (std::min)(current_wait * 2, config_.max_wait);
+        current_wait = std::min(current_wait * 2, config_.max_wait);
       }
     }
 
@@ -135,7 +132,6 @@ private:
   connection_pool &pool_;
   size_t connection_id_{};
   retry_config config_{};
-  utils::message_bus &bus_;
 };
 
 }
@@ -182,7 +178,7 @@ utils::result<statement, utils::error> statement_cache::acquire(const query_cont
   const auto it = cache_map_.insert({
     key,
     {statement{
-      std::make_shared<internal::statement_cache_proxy>(bus_, std::move(stmt), pool_, id)},
+      std::make_shared<internal::statement_cache_proxy>(std::move(stmt), pool_, id)},
       std::chrono::steady_clock::now(),
       usage_list_.begin()}
   }).first;

test/orm/backend/test_statement.cpp

@@ -2,7 +2,6 @@
 #include "test_result_reader.hpp"
 #include "test_parameter_binder.hpp"
 
-#include <chrono>
 #include <random>
 #include <thread>
 
@@ -10,7 +9,7 @@ namespace matador::test::orm {
 test_statement::test_statement(const sql::query_context &query)
 : statement_impl(query) {}
 
-utils::result<size_t, utils::error> test_statement::execute(const sql::parameter_binder &/*bindings*/) {
+utils::result<size_t, utils::error> test_statement::execute(const sql::interface::parameter_binder &/*bindings*/) {
   using namespace std::chrono_literals;
   std::mt19937 rng(query_.sql.size());
   std::uniform_int_distribution dist(10, 40);
@@ -18,7 +17,7 @@ utils::result<size_t, utils::error> test_statement::execute(const sql::parameter
   return utils::ok(static_cast<size_t>(8));
 }
 
-utils::result<std::unique_ptr<sql::query_result_impl>, utils::error> test_statement::fetch(const sql::parameter_binder &/*bindings*/) {
+utils::result<std::unique_ptr<sql::query_result_impl>, utils::error> test_statement::fetch(const sql::interface::parameter_binder &/*bindings*/) {
   return utils::ok(std::make_unique<sql::query_result_impl>(std::make_unique<test_result_reader>(), query_.prototype, query_.prototype.size()));
 }
 

test/orm/backend/test_statement.hpp

@@ -8,8 +8,8 @@ namespace matador::test::orm {
 class test_statement final : public sql::statement_impl {
 public:
   explicit test_statement(const sql::query_context &query);
-  utils::result<size_t, utils::error> execute(const sql::parameter_binder &bindings) override;
-  utils::result<std::unique_ptr<sql::query_result_impl>, utils::error> fetch(const sql::parameter_binder &bindings) override;
+  utils::result<size_t, utils::error> execute(const sql::interface::parameter_binder &bindings) override;
+  utils::result<std::unique_ptr<sql::query_result_impl>, utils::error> fetch(const sql::interface::parameter_binder &bindings) override;
   void reset() override;
 
 protected:

test/orm/sql/StatementCacheTest.cpp

@@ -22,57 +22,54 @@ using namespace matador::sql;
 using namespace matador::query;
 using namespace matador::utils;
 
-class MetricsObserver {
-public:
-  MetricsObserver(message_bus &bus) {
-
-  }
-  void on_event(const statement_cache_event& evt) override {
-    std::lock_guard<std::mutex> lock(mutex_);
-
-    switch (evt.type) {
-      case statement_cache_event::Type::LockFailed:
-        lock_failure_count_++;
-        if (evt.duration) {
-          total_lock_wait_time_ += evt.duration.value();
-        }
-        break;
-
-      case statement_cache_event::Type::ExecutionEnded:
-        execution_count_++;
-        if (evt.duration) {
-          total_execution_time_ += evt.duration.value();
-        }
-        break;
-    }
-  }
-
-  // Metrik-Zugriffsmethoden
-  double get_average_lock_wait_time() const {
-    std::lock_guard lock(mutex_);
-    if (lock_failure_count_ == 0) return 0.0;
-    return std::chrono::duration<double>(total_lock_wait_time_).count() / lock_failure_count_;
-  }
-
-  double get_average_execution_time() const {
-    std::lock_guard lock(mutex_);
-    if (execution_count_ == 0) return 0.0;
-    return std::chrono::duration<double>(total_execution_time_).count() / execution_count_;
-  }
-
-  size_t get_lock_failure_count() const {
-    std::lock_guard lock(mutex_);
-    return lock_failure_count_;
-  }
-
-private:
-  mutable std::mutex mutex_;
-  size_t lock_failure_count_{0};
-  size_t execution_count_{0};
-  std::chrono::nanoseconds total_lock_wait_time_{0};
-  std::chrono::nanoseconds total_execution_time_{0};
-};
-
+// Beispiel für einen Observer, der die Metriken auswertet
+// class MetricsObserver : public statement_cache_observer_interface {
+// public:
+//   void on_event(const statement_cache_event& evt) override {
+//     std::lock_guard<std::mutex> lock(mutex_);
+//
+//     switch (evt.type) {
+//       case statement_cache_event::Type::LockFailed:
+//         lock_failure_count_++;
+//         if (evt.duration) {
+//           total_lock_wait_time_ += evt.duration.value();
+//         }
+//         break;
+//
+//       case statement_cache_event::Type::ExecutionEnded:
+//         execution_count_++;
+//         if (evt.duration) {
+//           total_execution_time_ += evt.duration.value();
+//         }
+//         break;
+//     }
+//   }
+//
+//   // Metrik-Zugriffsmethoden
+//   double get_average_lock_wait_time() const {
+//     std::lock_guard<std::mutex> lock(mutex_);
+//     if (lock_failure_count_ == 0) return 0.0;
+//     return std::chrono::duration<double>(total_lock_wait_time_).count() / lock_failure_count_;
+//   }
+//
+//   double get_average_execution_time() const {
+//     std::lock_guard<std::mutex> lock(mutex_);
+//     if (execution_count_ == 0) return 0.0;
+//     return std::chrono::duration<double>(total_execution_time_).count() / execution_count_;
+//   }
+//
+//   size_t get_lock_failure_count() const {
+//     std::lock_guard<std::mutex> lock(mutex_);
+//     return lock_failure_count_;
+//   }
+//
+// private:
+//   mutable std::mutex mutex_;
+//   size_t lock_failure_count_{0};
+//   size_t execution_count_{0};
+//   std::chrono::nanoseconds total_lock_wait_time_{0};
+//   std::chrono::nanoseconds total_execution_time_{0};
+// };
 // void example_with_metrics() {
 //   connection_pool pool("noop://noop.db", 4);
 //   statement_cache cache(pool, 5);
@@ -307,10 +304,9 @@ TEST_CASE("Race condition simulation with mixed access", "[statement_cache][race
 
   auto task = [&](int /*id*/) {
     for (int i = 0; i < operations; ++i) {
-      const auto sql = "SELECT " + std::to_string(i % 10);
-      if (const auto result = cache.acquire({sql}); !result) {
-        FAIL("Statement should not be available");
-      }
+      auto sql = "SELECT " + std::to_string(i % 10);
+      auto result = cache.acquire({sql});
+      REQUIRE(result);
 
       // if (i % 50 == 0) {
         // cache.cleanup_expired_connections();