added sqlite connection class (progress)

CMakeLists.txt

@@ -2,15 +2,24 @@ cmake_minimum_required(VERSION 3.26)
 project(query)
 
 set(CMAKE_CXX_STANDARD 17)
-
-include_directories(${PROJECT_SOURCE_DIR}/include)
+set(CMAKE_POSITION_INDEPENDENT_CODE ON)
 
 find_package(ODBC REQUIRED)
+find_package(SQLite3 REQUIRED)
+
+message(STATUS "Found SQLite3 ${SQLite3_VERSION}")
+message(STATUS "Adding SQLite3 include directory: ${SQLite3_INCLUDE_DIRS}")
+message(STATUS "Adding SQLite3 libs: ${SQLite3_LIBRARIES}")
+
+message(STATUS "Common flags ${CMAKE_CXX_FLAGS}")
+message(STATUS "Debug flags ${CMAKE_CXX_FLAGS_DEBUG}")
+message(STATUS "Relase flags ${CMAKE_CXX_FLAGS_RELEASE}")
+
+message(STATUS "Linker flags ${CMAKE_EXE_LINKER_FLAGS}")
 
 add_subdirectory(src)
 add_subdirectory(test)
+add_subdirectory(backends)
 
-add_executable(query main.cpp
-  include/matador/sql/connection_impl.hpp
-  include/matador/sql/connection_info.hpp)
+add_executable(query main.cpp)
 target_link_libraries(query matador)

backends/CMakeLists.txt

@@ -0,0 +1 @@
+add_subdirectory(sqlite)

backends/sqlite/CMakeLists.txt

@@ -0,0 +1,17 @@
+set(HEADER
+  include/sqlite_connection.hpp
+  include/sqlite_error.hpp
+)
+
+set(SOURCES
+  src/sqlite_connection.cpp
+  src/sqlite_error.cpp
+)
+
+add_library(matador-sqlite SHARED ${SOURCES} ${HEADER})
+target_include_directories(matador-sqlite PRIVATE
+  ${PROJECT_SOURCE_DIR}/include
+  ${PROJECT_SOURCE_DIR}/backends/sqlite/include
+  ${SQLite3_INCLUDE_DIRS})
+
+target_link_libraries(matador-sqlite matador ${SQLite3_LIBRARIES})

backends/sqlite/include/sqlite_connection.hpp

@@ -0,0 +1,26 @@
+#ifndef QUERY_SQLITE_CONNECTION_HPP
+#define QUERY_SQLITE_CONNECTION_HPP
+
+#include "matador/sql/connection_impl.hpp"
+
+#include <sqlite3.h>
+
+namespace matador::backends::sqlite {
+
+class sqlite_connection : public matador::sql::connection_impl
+{
+public:
+  explicit sqlite_connection(sql::connection_info info);
+  void open() override;
+  void close() override;
+  bool is_open() override;
+
+  void execute(const std::string &stmt) override;
+  void prepare(const std::string &stmt) override;
+
+private:
+  sqlite3 *sqlite_db_{};
+};
+
+}
+#endif //QUERY_SQLITE_CONNECTION_HPP

backends/sqlite/include/sqlite_error.hpp

@@ -0,0 +1,15 @@
+#ifndef QUERY_SQLITE_ERROR_HPP
+#define QUERY_SQLITE_ERROR_HPP
+
+#include <string>
+
+struct sqlite3;
+
+namespace matador::backends::sqlite {
+
+void throw_sqlite_error(int ec, sqlite3 *db, const std::string &source);
+void throw_sqlite_error(int ec, sqlite3 *db, const std::string &source, const std::string &sql);
+
+}
+
+#endif //QUERY_SQLITE_ERROR_HPP

backends/sqlite/src/sqlite_connection.cpp

@@ -0,0 +1,46 @@
+#include "sqlite_connection.hpp"
+#include "sqlite_error.hpp"
+
+#include <utility>
+
+namespace matador::backends::sqlite {
+
+sqlite_connection::sqlite_connection(sql::connection_info info)
+: connection_impl(std::move(info)) {
+
+}
+
+void sqlite_connection::open()
+{
+  const auto ret = sqlite3_open(info().database.c_str(), &sqlite_db_);
+
+  if (ret != SQLITE_OK) {
+    throw_sqlite_error(ret, sqlite_db_, "open");
+  }
+}
+
+void sqlite_connection::close()
+{
+  int ret = sqlite3_close(sqlite_db_);
+
+  throw_sqlite_error(ret, sqlite_db_, "close");
+
+  sqlite_db_ = nullptr;
+}
+
+bool sqlite_connection::is_open()
+{
+  return false;
+}
+
+void sqlite_connection::execute(const std::string &stmt)
+{
+
+}
+
+void sqlite_connection::prepare(const std::string &stmt)
+{
+
+}
+
+}

backends/sqlite/src/sqlite_error.cpp

@@ -0,0 +1,28 @@
+#include "sqlite_error.hpp"
+
+#include <stdexcept>
+#include <sstream>
+
+#include <sqlite3.h>
+
+namespace matador::backends::sqlite {
+
+void throw_sqlite_error(int ec, sqlite3 *db, const std::string &source)
+{
+  if (ec != SQLITE_OK) {
+    std::stringstream msg;
+    msg << "sqlite error (" << source << "): " << sqlite3_errmsg(db);
+    throw std::logic_error(msg.str());
+  }
+}
+
+void throw_sqlite_error(int ec, sqlite3 *db, const std::string &source, const std::string &sql)
+{
+  if (ec != SQLITE_OK) {
+    std::stringstream msg;
+    msg << "sqlite error (" << source << ", sql: " << sql << "): " << sqlite3_errmsg(db);
+    throw std::logic_error(msg.str());
+  }
+}
+
+}

include/matador/sql/connection.hpp

@@ -1,7 +1,7 @@
 #ifndef QUERY_CONNECTION_HPP
 #define QUERY_CONNECTION_HPP
 
-#include "matador/sql/connection_intermediates.hpp"
+#include "matador/sql/query_intermediates.hpp"
 #include "matador/sql/dialect.hpp"
 #include "matador/sql/query_builder.hpp"
 
@@ -12,20 +12,21 @@ namespace matador::sql {
 class connection
 {
 public:
-  connection();
-  query_create_intermediate create();
-  query_drop_intermediate drop();
-  query_select_intermediate select(std::initializer_list<std::string> column_names);
-  query_insert_intermediate insert();
-  query_update_intermediate update(const std::string &table);
-  query_delete_intermediate remove();
+  connection() = default;
+  explicit connection(std::string dns);
+
+  void open();
+  void close();
+  [[nodiscard]] bool is_open() const;
+
+  [[nodiscard]] const std::string& dns() const;
 
   query_result<record> fetch(const std::string &sql);
   std::pair<size_t, std::string> execute(const std::string &sql);
 
 private:
-  dialect dialect_;
-  query_builder query_;
+  std::string dns_;
+  bool is_open_{false};
 };
 
 }

include/matador/sql/connection_pool.hpp

@@ -0,0 +1,107 @@
+#ifndef QUERY_CONNECTION_POOL_HPP
+#define QUERY_CONNECTION_POOL_HPP
+
+#include <utility>
+#include <queue>
+#include <mutex>
+#include <string>
+#include <unordered_set>
+
+namespace matador::sql {
+
+template < class Connection >
+class connection_pool;
+
+template < class Connection >
+class connection_ptr
+{
+public:
+  connection_ptr(Connection *c, connection_pool<Connection> &pool)
+  : connection_(c), pool_(pool) {}
+  ~connection_ptr();
+  connection_ptr(const connection_ptr &) = delete;
+  connection_ptr& operator=(const connection_ptr &) = delete;
+  connection_ptr(connection_ptr &&) noexcept = default;
+  connection_ptr& operator=(connection_ptr &&) noexcept = default;
+
+  Connection* operator->() { return connection_; }
+  Connection& operator*() { return *connection_; }
+
+  [[nodiscard]] bool valid() const { return connection_ != nullptr; }
+
+private:
+  friend class connection_pool<Connection>;
+
+  Connection *connection_;
+  connection_pool<Connection> &pool_;
+};
+
+template < class Connection >
+class connection_pool
+{
+public:
+  connection_pool(const std::string &db, unsigned int count) {
+    connection_repo_.reserve(count);
+    for (auto i = 0U; i < count; ++i) {
+      connection_repo_.emplace_back(db + std::to_string(i+1));
+      idle_connections_.push(&connection_repo_.back());
+      idle_connections_.back()->open();
+    }
+  }
+
+  connection_ptr<Connection> acquire() {
+    std::lock_guard<std::mutex> guard(mutex_);
+    if (idle_connections_.empty()) {
+      return {nullptr, *this};
+    }
+
+    auto ptr = idle_connections_.front();
+    idle_connections_.pop();
+    inuse_connections_.insert(ptr);
+    return { ptr, *this };
+  }
+
+  void release(Connection *c) {
+    if (c == nullptr) {
+      return;
+    }
+    std::lock_guard<std::mutex> guard(mutex_);
+
+    if (inuse_connections_.erase(c) > 0) {
+      idle_connections_.push(c);
+    }
+  }
+
+  void release(connection_ptr<Connection> &c) {
+    release(c.connection_);
+    c.connection_ = nullptr;
+  }
+  
+  std::size_t size() const { return connection_repo_.size(); }
+  std::size_t idle() const {
+    std::lock_guard<std::mutex> guard(mutex_);
+    return idle_connections_.size();
+  }
+  std::size_t inuse() const {
+    std::lock_guard<std::mutex> guard(mutex_);
+    return inuse_connections_.size();
+  }
+
+private:
+  mutable std::mutex mutex_;
+  std::vector<Connection> connection_repo_;
+  using pointer = Connection*;
+  using connections = std::queue<pointer>;
+  using connection_set = std::unordered_set<pointer>;
+  connections idle_connections_;
+  connection_set inuse_connections_;
+};
+
+template<class Connection>
+connection_ptr<Connection>::~connection_ptr() {
+  pool_.release(connection_);
+}
+
+}
+
+#endif //QUERY_CONNECTION_POOL_HPP

include/matador/sql/query_intermediates.hpp

@@ -1,5 +1,5 @@
-#ifndef QUERY_CONNECTION_INTERMEDIATES_HPP
-#define QUERY_CONNECTION_INTERMEDIATES_HPP
+#ifndef QUERY_QUERY_INTERMEDIATES_HPP
+#define QUERY_QUERY_INTERMEDIATES_HPP
 
 #include "matador/sql/column.hpp"
 #include "matador/sql/key_value_pair.hpp"
@@ -11,20 +11,20 @@
 namespace matador::sql {
 
 class basic_condition;
-class connection;
+class session;
 class query_builder;
 
 class query_intermediate
 {
 public:
-  query_intermediate(connection &db, query_builder &query);
+  query_intermediate(session &db, query_builder &query);
 
 protected:
-  connection& db();
+  session& db();
   query_builder& query();
 
 private:
-  connection &db_;
+  session &db_;
   query_builder &query_;
 };
 
@@ -195,4 +195,4 @@ public:
 };
 
 }
-#endif //QUERY_CONNECTION_INTERMEDIATES_HPP
+#endif //QUERY_QUERY_INTERMEDIATES_HPP

include/matador/sql/session.hpp

@@ -0,0 +1,31 @@
+#ifndef QUERY_SESSION_HPP
+#define QUERY_SESSION_HPP
+
+#include "matador/sql/connection.hpp"
+#include "matador/sql/connection_pool.hpp"
+
+namespace matador::sql {
+
+class session
+{
+public:
+  explicit session(connection_pool<connection> &pool);
+
+  query_create_intermediate create();
+  query_drop_intermediate drop();
+  query_select_intermediate select(std::initializer_list<std::string> column_names);
+  query_insert_intermediate insert();
+  query_update_intermediate update(const std::string &table);
+  query_delete_intermediate remove();
+
+  query_result<record> fetch(const std::string &sql);
+  std::pair<size_t, std::string> execute(const std::string &sql);
+
+private:
+  connection_pool<connection> &pool_;
+  dialect dialect_;
+  query_builder query_;
+};
+
+}
+#endif //QUERY_SESSION_HPP

include/matador/utils/library.hpp

@@ -0,0 +1,107 @@
+#ifndef QUERY_LIBRARY_HPP
+#define QUERY_LIBRARY_HPP
+
+#include <string>
+
+#if defined(_MSC_VER) || defined(__MINGW32__)
+#define _WINSOCKAPI_
+#include <windows.h>
+#else
+#include <dlfcn.h>
+#endif
+
+namespace matador::utils {
+
+#ifndef MATADOR_DOXYGEN_DOC
+#if defined(_MSC_VER) || defined(__MINGW32__)
+typedef FARPROC func_ptr;
+#else
+typedef void *func_ptr;
+#endif
+#endif /* MATADOR_DOXYGEN_DOC */
+
+/**
+ * @class library
+ * @brief Helps to load and unload
+ *        external libraries.
+ *
+ * This class represents a loader and un-loader
+ * for an external library. The path to the library
+ * is given by a string.
+ * It can be loaded and unloaded. Furthermore it
+ * provides a method to get a pointer to an function
+ * exported by the library. The function is identified
+ * by a name.
+ */
+class library
+{
+public:
+  /**
+   * Create a unspecified library serializable
+   */
+  library() = default;
+
+  /**
+   * Create a library for the given lib path
+   *
+   * @param lib The path to the library to map.
+   */
+  explicit library(std::string lib);
+
+  ~library();
+
+  /**
+   * Load the underlying library.
+   * If the library path is invalid
+   * or the library cannot be loaded
+   * false is returned.
+   *
+   * @return True on successful library loading.
+   */
+  bool load();
+
+  /**
+   * Sets the library (and subsequently close and
+   * overwrite an already instantiated library) and
+   * load the underlying library. If the library
+   * path is invalid or the library cannot be loaded
+   * false is returned.
+   *
+   * @param lib The path to the library to load.
+   * @return True on successful library loading.
+   */
+  bool load(const std::string &lib);
+
+  /**
+   * Unload an loaded library. If
+   * the library isn't loaded or an
+   * error occurred while unloading
+   * false is returned.
+   *
+   * @return True on successful unloading.
+   */
+  bool unload();
+
+  /**
+   * Returns the pointer to the exported
+   * function of the library identified
+   * by the given name.
+   *
+   * @param f The name of the exported function.
+   * @return The pointer to the function.
+   */
+  [[nodiscard]] func_ptr function(const std::string &f) const;
+
+private:
+  std::string lib_;
+
+#if defined(_WIN32) || defined(__MINGW32__)
+  HMODULE handle_ = nullptr;
+#else
+  void *handle_ = nullptr;
+#endif
+};
+
+}
+
+#endif //QUERY_LIBRARY_HPP

src/CMakeLists.txt

@@ -5,10 +5,11 @@ set(SQL_SOURCES
   sql/key_value_pair.cpp
   sql/basic_condition.cpp
   sql/connection.cpp
-  sql/connection_intermediates.cpp
+  sql/query_intermediates.cpp
   sql/record.cpp
   sql/connection_info.cpp
-  sql/connection_impl.cpp)
+  sql/connection_impl.cpp
+  sql/session.cpp)
 
 set(SQL_HEADER
   ../include/matador/sql/dialect.hpp
@@ -19,22 +20,27 @@ set(SQL_HEADER
   ../include/matador/sql/basic_condition.hpp
   ../include/matador/sql/condition.hpp
   ../include/matador/sql/connection.hpp
-  ../include/matador/sql/connection_intermediates.hpp
+  ../include/matador/sql/query_intermediates.hpp
   ../include/matador/sql/result.hpp
   ../include/matador/sql/record.hpp
   ../include/matador/sql/query_result.hpp
   ../include/matador/sql/connection_impl.hpp
-  ../include/matador/sql/connection_info.hpp)
+  ../include/matador/sql/connection_info.hpp
+  ../include/matador/sql/connection_pool.hpp
+  ../include/matador/sql/session.hpp)
 
 set(UTILS_HEADER
   ../include/matador/utils/field_attributes.hpp
   ../include/matador/utils/string.hpp
-  ../include/matador/utils/constraints.hpp)
+  ../include/matador/utils/constraints.hpp
+  ../include/matador/utils/library.hpp)
 
 set(UTILS_SOURCES
   utils/field_attributes.cpp
   utils/string.cpp
-  sql/condition.cpp)
+  sql/condition.cpp
+  utils/library.cpp)
 
 add_library(matador STATIC ${SQL_SOURCES} ${SQL_HEADER} ${UTILS_SOURCES} ${UTILS_HEADER})
-set_target_properties(matador PROPERTIES LINKER_LANGUAGE CXX)
+target_include_directories(matador PUBLIC ${PROJECT_SOURCE_DIR}/include)
+#set_target_properties(matador PROPERTIES LINKER_LANGUAGE CXX)

src/sql/connection.cpp

@@ -1,39 +1,30 @@
+#include <utility>
+
 #include "matador/sql/connection.hpp"
 
 namespace matador::sql {
 
+connection::connection(std::string dns)
+: dns_(std::move(dns)) {}
 
-connection::connection()
-: query_(dialect_) {}
-
-query_create_intermediate connection::create()
+void connection::open()
 {
-  return query_create_intermediate{*this, query_.create()};
+  is_open_ = true;
 }
 
-query_drop_intermediate connection::drop()
+void connection::close()
 {
-  return query_drop_intermediate{*this, query_.drop()};
+  is_open_ = false;
 }
 
-query_select_intermediate connection::select(std::initializer_list<std::string> column_names)
+bool connection::is_open() const
 {
-  return query_select_intermediate{*this, query_.select(column_names)};
+  return is_open_;
 }
 
-query_insert_intermediate connection::insert()
+const std::string &connection::dns() const
 {
-  return query_insert_intermediate{*this, query_.insert()};
-}
-
-query_update_intermediate connection::update(const std::string &table)
-{
-  return query_update_intermediate{*this, query_.update(table)};
-}
-
-query_delete_intermediate connection::remove()
-{
-  return query_delete_intermediate{*this, query_.remove()};
+  return dns_;
 }
 
 query_result<record> connection::fetch(const std::string &sql)

src/sql/query_intermediates.cpp

@@ -1,9 +1,9 @@
-#include "matador/sql/connection_intermediates.hpp"
-#include "matador/sql/connection.hpp"
+#include "matador/sql/query_intermediates.hpp"
+#include "matador/sql/session.hpp"
 #include "matador/sql/query_builder.hpp"
 
 namespace matador::sql {
-connection &query_intermediate::db()
+session &query_intermediate::db()
 {
   return db_;
 }
@@ -23,7 +23,7 @@ record query_select_finish::fetch_one()
   return db().fetch(query().compile()).begin();
 }
 
-query_intermediate::query_intermediate(connection &db, query_builder &query)
+query_intermediate::query_intermediate(session &db, query_builder &query)
 : db_(db), query_(query) {}
 
 query_offset_intermediate query_order_direction_intermediate::offset(size_t offset)

src/sql/session.cpp

@@ -0,0 +1,56 @@
+#include "matador/sql/session.hpp"
+
+#include <stdexcept>
+
+namespace matador::sql {
+
+session::session(connection_pool<connection> &pool)
+: pool_(pool)
+, query_(dialect_) {}
+
+query_create_intermediate session::create()
+{
+  return query_create_intermediate{*this, query_.create()};
+}
+
+query_drop_intermediate session::drop()
+{
+  return query_drop_intermediate{*this, query_.drop()};
+}
+
+query_select_intermediate session::select(std::initializer_list<std::string> column_names)
+{
+  return query_select_intermediate{*this, query_.select(column_names)};
+}
+
+query_insert_intermediate session::insert()
+{
+  return query_insert_intermediate{*this, query_.insert()};
+}
+
+query_update_intermediate session::update(const std::string &table)
+{
+  return query_update_intermediate{*this, query_.update(table)};
+}
+
+query_delete_intermediate session::remove()
+{
+  return query_delete_intermediate{*this, query_.remove()};
+}
+
+query_result<record> session::fetch(const std::string &sql) {
+  auto c = pool_.acquire();
+  if (!c.valid()) {
+    throw std::logic_error("no database connection available");
+  }
+  return c->fetch(sql);
+}
+
+std::pair<size_t, std::string> session::execute(const std::string &sql) {
+  auto c = pool_.acquire();
+  if (!c.valid()) {
+    throw std::logic_error("no database connection available");
+  }
+  return c->execute(sql);
+}
+}

src/utils/library.cpp

@@ -0,0 +1,70 @@
+#include "matador/utils/library.hpp"
+
+namespace matador::utils {
+
+library::library(std::string lib)
+  : lib_(std::move(lib))
+{}
+
+library::~library()
+{
+  unload();
+}
+
+bool library::load()
+{
+#if defined(_MSC_VER) || defined(__MINGW32__)
+  handle_ = LoadLibrary((lib_ + ".dll").c_str());
+#elif defined(__APPLE__)
+  handle_ = dlopen(std::string("lib" + lib_ + ".dylib").c_str(), RTLD_LAZY);
+#else
+  handle_ = dlopen(std::string("./lib" + lib_ + ".so").c_str(), RTLD_LAZY);
+#endif
+  if (!handle_) {
+#if defined(_MSC_VER) || defined(__MINGW32__)
+    DWORD errorMessageID = ::GetLastError();
+#else
+    // TODO: handle win32 and linux error
+    fprintf(stdout, "dlopen error: %s", dlerror());
+#endif
+    return false;
+  }
+  return true;
+}
+
+bool library::load(const std::string &lib)
+{
+  if (handle_) {
+    return false;
+  }
+  lib_ = lib;
+  return load();
+}
+
+bool library::unload()
+{
+  bool ret(true);
+  if (handle_) {
+#if defined(_MSC_VER) || defined(__MINGW32__)
+    ret = FreeLibrary(handle_) == TRUE;
+#else
+    ret = dlclose(handle_) == 0;
+#endif
+    if (!ret) {
+    } else {
+      handle_ = nullptr;
+    }
+  }
+  return ret;
+}
+
+func_ptr library::function(const std::string &f) const
+{
+#if defined(_MSC_VER) || defined(__MINGW32__)
+  return GetProcAddress(handle_, f.c_str());
+#else
+  return dlsym(handle_, f.c_str());
+#endif
+}
+
+}

test/CMakeLists.txt

@@ -9,7 +9,9 @@ FetchContent_Declare(
 FetchContent_MakeAvailable(Catch2)
 
 add_executable(tests builder.cpp
-  connection.cpp
-  record.cpp)
+  session.cpp
+  record.cpp
+  connection_pool.cpp
+  query.cpp)
 target_link_libraries(tests PRIVATE Catch2::Catch2WithMain matador)
 target_include_directories(tests PUBLIC $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}>/include)

test/connection_pool.cpp

@@ -0,0 +1,42 @@
+#include <catch2/catch_test_macros.hpp>
+
+#include <matador/sql/connection.hpp>
+#include <matador/sql/connection_pool.hpp>
+
+using namespace matador::sql;
+
+TEST_CASE("Create connection pool", "[connection pool]") {
+  using pool_t = connection_pool<connection>;
+
+  pool_t pool("db", 4);
+
+  REQUIRE(pool.size() == 4);
+  REQUIRE(pool.idle() == 4);
+  REQUIRE(pool.inuse() == 0);
+
+  auto ptr = pool.acquire();
+  REQUIRE(ptr.valid());
+  REQUIRE(ptr->is_open());
+  REQUIRE(!ptr->dns().empty());
+
+  REQUIRE(pool.idle() == 3);
+  REQUIRE(pool.inuse() == 1);
+
+  pool.release(ptr);
+  REQUIRE(!ptr.valid());
+  REQUIRE(pool.idle() == 4);
+  REQUIRE(pool.inuse() == 0);
+
+  {
+    auto ptr2 = pool.acquire();
+    REQUIRE(ptr2.valid());
+    REQUIRE(ptr2->is_open());
+    REQUIRE(!ptr2->dns().empty());
+
+    REQUIRE(pool.idle() == 3);
+    REQUIRE(pool.inuse() == 1);
+  }
+
+  REQUIRE(pool.idle() == 4);
+  REQUIRE(pool.inuse() == 0);
+}

test/query.cpp

@@ -0,0 +1,9 @@
+#include <catch2/catch_test_macros.hpp>
+#include "catch2/generators/catch_generators.hpp"
+
+TEST_CASE("Query test", "[query]") {
+  auto dns = GENERATE(as<std::string>{}, "mssql", "sqlite", "postgres" );
+
+  INFO(dns);
+  REQUIRE(!dns.empty());
+}

test/session.cpp

@@ -2,14 +2,15 @@
 
 #include <matador/sql/column.hpp>
 #include <matador/sql/condition.hpp>
-#include <matador/sql/connection.hpp>
+#include <matador/sql/session.hpp>
 
 using namespace matador::sql;
 
 TEST_CASE("Execute create table statement", "[connection]") {
-  connection c;
+  connection_pool<connection> pool("dns", 4);
+  session s(pool);
 
-  const auto res = c.create()
+  const auto res = s.create()
    .table("person", {
      make_pk_column<unsigned long>("id"),
      make_column<std::string>("name", 255),
@@ -21,9 +22,10 @@ TEST_CASE("Execute create table statement", "[connection]") {
 }
 
 TEST_CASE("Execute drop table statement", "[connection]") {
-  connection c;
+  connection_pool<connection> pool("dns", 4);
+  session s(pool);
 
-  const auto res = c.drop()
+  const auto res = s.drop()
                     .table("person")
                     .execute();
 
@@ -31,9 +33,10 @@ TEST_CASE("Execute drop table statement", "[connection]") {
 }
 
 TEST_CASE("Execute select statement with where clause", "[connection]") {
-  connection c;
+  connection_pool<connection> pool("dns", 4);
+  session s(pool);
 
-  auto res = c.select({"id", "name", "color"})
+  auto res = s.select({"id", "name", "color"})
               .from("person")
               .where("id"_col == 8)
               .fetch_all();
@@ -42,9 +45,10 @@ TEST_CASE("Execute select statement with where clause", "[connection]") {
 }
 
 TEST_CASE("Execute select statement with order by", "[connection]") {
-  connection c;
+  connection_pool<connection> pool("dns", 4);
+  session s(pool);
 
-  auto res = c.select({"id", "name", "color"})
+  auto res = s.select({"id", "name", "color"})
               .from("person")
               .where("id"_col == 8)
               .order_by("name").desc()
@@ -54,9 +58,10 @@ TEST_CASE("Execute select statement with order by", "[connection]") {
 }
 
 TEST_CASE("Execute select statement with group by and order by", "[connection]") {
-  connection c;
+  connection_pool<connection> pool("dns", 4);
+  session s(pool);
 
-  auto res = c.select({"id", "name", "color"})
+  auto res = s.select({"id", "name", "color"})
               .from("person")
               .where("id"_col == 8)
               .group_by("color")
@@ -67,9 +72,10 @@ TEST_CASE("Execute select statement with group by and order by", "[connection]")
 }
 
 TEST_CASE("Execute insert statement", "[connection]") {
-  connection c;
+  connection_pool<connection> pool("dns", 4);
+  session s(pool);
 
-  auto res = c.insert()
+  auto res = s.insert()
               .into("person", {"id", "name", "color"})
               .values({7, "george", "green"})
               .execute();
@@ -78,9 +84,10 @@ TEST_CASE("Execute insert statement", "[connection]") {
 }
 
 TEST_CASE("Execute update statement", "[connection]") {
-  connection c;
+  connection_pool<connection> pool("dns", 4);
+  session s(pool);
 
-  auto res = c.update("person")
+  auto res = s.update("person")
               .set({
                      {"name",  "george"},
                      {"color", "green"}
@@ -92,9 +99,10 @@ TEST_CASE("Execute update statement", "[connection]") {
 }
 
 TEST_CASE("Execute delete statement", "[connection]") {
-  connection c;
+  connection_pool<connection> pool("dns", 4);
+  session s(pool);
 
-  auto res = c.remove()
+  auto res = s.remove()
               .from("person", "p")
               .where("id"_col == 9)
               .execute();