fixed a bug when acquiring a connection with a specific id

include/matador/sql/connection_pool.hpp

@@ -19,7 +19,7 @@ template < class Connection >
 class connection_ptr
 {
 public:
-  connection_ptr(IdConnection<Connection> *c, connection_pool<Connection> &pool)
+  connection_ptr(IdConnection<Connection> *c, connection_pool<Connection> *pool)
   : connection_(c), pool_(pool) {}
   ~connection_ptr();
   connection_ptr(const connection_ptr &) = delete;
@@ -29,15 +29,16 @@ public:
   , pool_(x.pool_)
   {
     x.connection_ = nullptr;
+    x.pool_ = nullptr;
   }
   connection_ptr& operator=(connection_ptr &&x) noexcept
   {
     if (this == &x) {
       return *this;
     }
-    connection_ = x.connection_;
-    pool_ = x.pool_;
-    x.connection_ = nullptr;
+
+    std::swap(connection_, x.connection_);
+    std::swap(pool_, x.pool_);
 
     return *this;
   }
@@ -52,8 +53,8 @@ public:
 private:
   friend class connection_pool<Connection>;
 
-  IdConnection<Connection> *connection_;
-  connection_pool<Connection> &pool_;
+  IdConnection<Connection> *connection_{};
+  connection_pool<Connection> *pool_{};
 };
 
 template < class Connection >
@@ -74,10 +75,10 @@ public:
     }
   }
 
-  connection_ptr<Connection> acquire() {
+  connection_pointer acquire() {
     std::unique_lock<std::mutex> lock(mutex_);
     if (idle_connections_.empty()) {
-      return {nullptr, *this};
+      return {nullptr, this};
     }
 
     pointer next_connection{nullptr};
@@ -87,10 +88,10 @@ public:
       inuse_connections_.insert(std::move(node));
       break;
     }
-    return {next_connection, *this};
+    return {next_connection, this};
   }
 
-  connection_ptr<Connection> acquire(size_t id) {
+  connection_pointer acquire(size_t id) {
     using namespace std::chrono_literals;
     pointer next_connection{nullptr};
     auto try_count{0};
@@ -98,17 +99,17 @@ public:
 
     do {
       if (auto it = idle_connections_.find(id); it != idle_connections_.end()) {
-        next_connection = it->second.second;
+        next_connection = it->second;
         auto node = idle_connections_.extract(it);
         inuse_connections_.insert(std::move(node));
       } else {
         lock.unlock();
-        std::this_thread::sleep_for(500ms);
+        std::this_thread::sleep_for(100ms);
         lock.lock();
       }
     } while(try_count++ < 5);
 
-    return {next_connection, *this};
+    return {next_connection, this};
   }
 
   void release(IdConnection<Connection> *c) {
@@ -153,7 +154,7 @@ private:
 
 template<class Connection>
 connection_ptr<Connection>::~connection_ptr() {
-  pool_.release(connection_);
+  pool_->release(connection_);
 }
 
 }