added sqlite db backend progress

backends/sqlite/CMakeLists.txt

@@ -1,11 +1,14 @@
 set(HEADER
   include/sqlite_connection.hpp
   include/sqlite_error.hpp
+  include/sqlite_dialect.hpp
+  include/sqlite_query_result.hpp
 )
 
 set(SOURCES
   src/sqlite_connection.cpp
   src/sqlite_error.cpp
+  src/sqlite_dialect.cpp
 )
 
 add_library(matador-sqlite SHARED ${SOURCES} ${HEADER})

backends/sqlite/include/sqlite_connection.hpp

@@ -1,6 +1,17 @@
 #ifndef QUERY_SQLITE_CONNECTION_HPP
 #define QUERY_SQLITE_CONNECTION_HPP
 
+#ifdef _MSC_VER
+#ifdef matador_sqlite_EXPORTS
+#define MATADOR_SQLITE_API __declspec(dllexport)
+#else
+#define MATADOR_SQLITE_API __declspec(dllimport)
+#endif
+#pragma warning(disable: 4355)
+#else
+#define MATADOR_SQLITE_API
+#endif
+
 #include "matador/sql/connection_impl.hpp"
 
 #include <sqlite3.h>
@@ -10,7 +21,7 @@ namespace matador::backends::sqlite {
 class sqlite_connection : public matador::sql::connection_impl
 {
 public:
-  explicit sqlite_connection(sql::connection_info info);
+  explicit sqlite_connection(const sql::connection_info &info);
   void open() override;
   void close() override;
   bool is_open() override;
@@ -23,4 +34,12 @@ private:
 };
 
 }
+
+extern "C"
+{
+MATADOR_SQLITE_API matador::sql::connection_impl* create_database(const matador::sql::connection_info &info);
+
+MATADOR_SQLITE_API void destroy_database(matador::sql::connection_impl *db);
+}
+
 #endif //QUERY_SQLITE_CONNECTION_HPP

backends/sqlite/include/sqlite_dialect.hpp

@@ -0,0 +1,19 @@
+#ifndef QUERY_SQLITE_DIALECT_HPP
+#define QUERY_SQLITE_DIALECT_HPP
+
+#ifdef _MSC_VER
+#ifdef matador_sqlite_EXPORTS
+#define MATADOR_SQLITE_API __declspec(dllexport)
+#else
+#define MATADOR_SQLITE_API __declspec(dllimport)
+#endif
+#pragma warning(disable: 4355)
+#else
+#define MATADOR_SQLITE_API
+#endif
+
+#include "matador/sql/dialect.hpp"
+
+extern "C" [[maybe_unused]] MATADOR_SQLITE_API const matador::sql::dialect* get_dialect();
+
+#endif //QUERY_SQLITE_DIALECT_HPP

backends/sqlite/include/sqlite_query_result.hpp

@@ -0,0 +1,13 @@
+#ifndef QUERY_SQLITE_QUERY_RESULT_HPP
+#define QUERY_SQLITE_QUERY_RESULT_HPP
+
+namespace matador::backends::sqlite {
+
+class sqlite_query_result {
+public:
+
+};
+
+}
+
+#endif //QUERY_SQLITE_QUERY_RESULT_HPP

backends/sqlite/src/sqlite_connection.cpp

@@ -5,9 +5,8 @@
 
 namespace matador::backends::sqlite {
 
-sqlite_connection::sqlite_connection(sql::connection_info info)
-: connection_impl(std::move(info)) {
-
+sqlite_connection::sqlite_connection(const sql::connection_info &info)
+: connection_impl(info) {
 }
 
 void sqlite_connection::open()
@@ -30,7 +29,7 @@ void sqlite_connection::close()
 
 bool sqlite_connection::is_open()
 {
-  return false;
+  return sqlite_db_ != nullptr;
 }
 
 void sqlite_connection::execute(const std::string &stmt)
@@ -44,3 +43,17 @@ void sqlite_connection::prepare(const std::string &stmt)
 }
 
 }
+
+extern "C"
+{
+MATADOR_SQLITE_API matador::sql::connection_impl *create_database(const matador::sql::connection_info &info)
+{
+  return new matador::backends::sqlite::sqlite_connection(info);
+}
+
+MATADOR_SQLITE_API void destroy_database(matador::sql::connection_impl *db)
+{
+  delete db;
+}
+
+}

backends/sqlite/src/sqlite_dialect.cpp

@@ -0,0 +1,11 @@
+#include "sqlite_dialect.hpp"
+
+[[maybe_unused]] const matador::sql::dialect* get_dialect() {
+  using namespace matador::sql;
+  const static dialect d{{
+             { dialect::token_t::BEGIN, "BEGIN TRANSACTION"},
+             { dialect::token_t::COMMIT, "COMMIT TRANSACTION"},
+             { dialect::token_t::ROLLBACK, "ROLLBACK TRANSACTION"}
+  }};
+  return &d;
+}

include/matador/sql/backend_provider.hpp

@@ -0,0 +1,53 @@
+#ifndef QUERY_BACKEND_PROVIDER_HPP
+#define QUERY_BACKEND_PROVIDER_HPP
+
+#include "matador/utils/library.hpp"
+
+#include <memory>
+#include <string>
+#include <unordered_map>
+
+namespace matador::sql {
+
+class connection_impl;
+struct connection_info;
+class dialect;
+
+class backend_provider
+{
+private:
+  backend_provider();
+
+public:
+  static backend_provider& instance();
+
+  connection_impl* create_connection(const std::string &connection_type, const connection_info &info);
+  void destroy_connection(const std::string &connection_type, connection_impl *c);
+  const dialect& connection_dialect(const std::string &connection_type);
+
+private:
+  struct backend_context {
+    backend_context(const std::string &connection_type,
+                    const std::string &backends_path);
+    backend_context(const backend_context&) = delete;
+    backend_context& operator=(const backend_context&) = delete;
+    backend_context(backend_context&&) noexcept = default;
+    backend_context& operator=(backend_context&&) noexcept = default;
+    ~backend_context();
+
+    typedef connection_impl*(*create_func)(const connection_info&);
+    typedef void (*destroy_func)(connection_impl*);
+    typedef const dialect*(*dialect_func)();
+
+    create_func create_connection{};
+    destroy_func destroy_connection{};
+    dialect_func get_dialect{};
+    utils::library lib;
+  };
+private:
+  using backends_t = std::unordered_map<std::string, std::unique_ptr<backend_context>>;
+  backends_t backends_;
+  std::string backends_path_;
+};
+}
+#endif //QUERY_BACKEND_PROVIDER_HPP

include/matador/sql/connection.hpp

@@ -1,32 +1,36 @@
 #ifndef QUERY_CONNECTION_HPP
 #define QUERY_CONNECTION_HPP
 
-#include "matador/sql/query_intermediates.hpp"
+#include "matador/sql/connection_info.hpp"
 #include "matador/sql/dialect.hpp"
-#include "matador/sql/query_builder.hpp"
+#include "matador/sql/query_result.hpp"
+#include "matador/sql/record.hpp"
 
 #include <string>
 
 namespace matador::sql {
 
+class connection_impl;
+
 class connection
 {
 public:
-  connection() = default;
-  explicit connection(std::string dns);
+  explicit connection(connection_info info);
+  explicit connection(const std::string& dns);
+  ~connection();
 
   void open();
   void close();
   [[nodiscard]] bool is_open() const;
-
-  [[nodiscard]] const std::string& dns() const;
+  [[nodiscard]] const connection_info& info() const;
 
   query_result<record> fetch(const std::string &sql);
   std::pair<size_t, std::string> execute(const std::string &sql);
 
 private:
-  std::string dns_;
+  const connection_info connection_info_;
   bool is_open_{false};
+  connection_impl *connection_{};
 };
 
 }

include/matador/sql/connection_impl.hpp

@@ -18,12 +18,12 @@ public:
   virtual void prepare(const std::string &stmt) = 0;
 
 protected:
-  explicit connection_impl(connection_info info);
+  explicit connection_impl(const connection_info &info);
 
   [[nodiscard]] const connection_info &info() const;
 
 private:
-  connection_info info_;
+  const connection_info & info_;
 };
 
 }

include/matador/sql/connection_pool.hpp

@@ -40,10 +40,11 @@ template < class Connection >
 class connection_pool
 {
 public:
-  connection_pool(const std::string &db, unsigned int count) {
+  connection_pool(const std::string &dns, unsigned int count)
+  : info_(connection_info::parse(dns)) {
     connection_repo_.reserve(count);
     for (auto i = 0U; i < count; ++i) {
-      connection_repo_.emplace_back(db + std::to_string(i+1));
+      connection_repo_.emplace_back(info_);
       idle_connections_.push(&connection_repo_.back());
       idle_connections_.back()->open();
     }
@@ -87,6 +88,9 @@ public:
     return inuse_connections_.size();
   }
 
+  const connection_info &info() const {
+    return info_;
+  }
 private:
   mutable std::mutex mutex_;
   std::vector<Connection> connection_repo_;
@@ -95,6 +99,8 @@ private:
   using connection_set = std::unordered_set<pointer>;
   connections idle_connections_;
   connection_set inuse_connections_;
+
+  const connection_info info_;
 };
 
 template<class Connection>

include/matador/sql/dialect.hpp

@@ -10,7 +10,7 @@
 
 namespace matador::sql {
 
-class [[nodiscard]] dialect
+class dialect
 {
 public:
   enum class token_t : uint8_t
@@ -59,7 +59,15 @@ public:
     ESCAPE_CLOSING_BRACKET  /**< The escape quotes differ; escape the closing one */
   };
 
+  using token_to_string_map = std::unordered_map<token_t, std::string>;
+  using data_type_to_string_map = std::unordered_map<data_type_t, std::string>;
+
 public:
+  dialect() = default;
+  dialect(const token_to_string_map &token_replace_map, const data_type_to_string_map &data_type_replace_map);
+  explicit dialect(const data_type_to_string_map &data_type_replace_map);
+  explicit dialect(const token_to_string_map &token_replace_map);
+
   const std::string& token_at(token_t token) const;
   const std::string& data_type_at(data_type_t type) const;
 
@@ -124,8 +132,6 @@ public:
   const std::vector<std::string>& columns() const;
 
 private:
-  using token_to_string_map = std::unordered_map<token_t, std::string>;
-
   std::vector<std::string> host_vars_;
   std::vector<std::string> columns_;
 
@@ -167,7 +173,6 @@ private:
     {token_t::NONE, ""}
   };
 
-  using data_type_to_string_map = std::unordered_map<data_type_t, std::string>;
   data_type_to_string_map data_types_ {
     {data_type_t::type_char, "TINYINT"},
     {data_type_t::type_short, "SMALLINT"},

include/matador/sql/query_result_impl.hpp

@@ -0,0 +1,60 @@
+#ifndef QUERY_QUERY_RESULT_IMPL_HPP
+#define QUERY_QUERY_RESULT_IMPL_HPP
+
+#include "matador/utils/field_attributes.hpp"
+
+#include <string>
+
+namespace matador::sql {
+
+class query_result_impl
+{
+public:
+  virtual void read_value(const char *id, size_t index, char &value) = 0;
+  virtual void read_value(const char *id, size_t index, short &value) = 0;
+  virtual void read_value(const char *id, size_t index, int &value) = 0;
+  virtual void read_value(const char *id, size_t index, long &value) = 0;
+  virtual void read_value(const char *id, size_t index, long long &value) = 0;
+  virtual void read_value(const char *id, size_t index, unsigned char &value) = 0;
+  virtual void read_value(const char *id, size_t index, unsigned short &value) = 0;
+  virtual void read_value(const char *id, size_t index, unsigned int &value) = 0;
+  virtual void read_value(const char *id, size_t index, unsigned long &value) = 0;
+  virtual void read_value(const char *id, size_t index, unsigned long long &value) = 0;
+  virtual void read_value(const char *id, size_t index, bool &value) = 0;
+  virtual void read_value(const char *id, size_t index, float &value) = 0;
+  virtual void read_value(const char *id, size_t index, double &value) = 0;
+//  virtual void read_value(const char *id, size_t index, matador::time &value) = 0;
+//  virtual void read_value(const char *id, size_t index, matador::date &value) = 0;
+  virtual void read_value(const char *id, size_t index, char *value, size_t s) = 0;
+  virtual void read_value(const char *id, size_t index, std::string &value) = 0;
+  virtual void read_value(const char *id, size_t index, std::string &value, size_t s) = 0;
+
+  template<typename ValueType>
+  void on_primary_key(const char *id, ValueType &value, typename std::enable_if<std::is_integral<ValueType>::value && !std::is_same<bool, ValueType>::value>::type* = 0)
+  {
+    read_value(id, column_index_++, value);
+  }
+  void on_primary_key(const char *id, std::string &value, size_t size);
+  void on_revision(const char *id, unsigned long long &rev);
+
+  template < class Type >
+  void on_attribute(const char *id, Type &x, const utils::field_attributes &/*attr*/ = utils::null_attributes)
+  {
+    read_value(id, column_index_++, x);
+  }
+  void on_attribute(const char *id, char *value, const utils::field_attributes &attr = utils::null_attributes);
+  void on_attribute(const char *id, std::string &value, const utils::field_attributes &attr = utils::null_attributes);
+
+//  void on_belongs_to(const char *id, matador::identifiable_holder &x, cascade_type);
+//  void on_has_one(const char *id, matador::identifiable_holder &x, cascade_type);
+
+//  void on_has_many(const char *, abstract_container &, const char *, const char *, cascade_type) {}
+//  void on_has_many(const char *, abstract_container &, cascade_type) {}
+
+protected:
+  size_t column_index_ = 0;
+};
+
+}
+
+#endif //QUERY_QUERY_RESULT_IMPL_HPP

include/matador/sql/session.hpp

@@ -3,6 +3,8 @@
 
 #include "matador/sql/connection.hpp"
 #include "matador/sql/connection_pool.hpp"
+#include "matador/sql/query_builder.hpp"
+#include "matador/sql/query_intermediates.hpp"
 
 namespace matador::sql {
 
@@ -23,7 +25,6 @@ public:
 
 private:
   connection_pool<connection> &pool_;
-  dialect dialect_;
   query_builder query_;
 };
 

include/matador/utils/os.hpp

@@ -0,0 +1,16 @@
+#ifndef QUERY_OS_HPP
+#define QUERY_OS_HPP
+
+#include <string>
+
+namespace matador::utils::os {
+
+std::string error_string(unsigned long error);
+
+std::string getenv(const char* name);
+
+[[maybe_unused]] std::string getenv(const std::string &name);
+
+}
+
+#endif //QUERY_OS_HPP

main.cpp

@@ -1,21 +1,17 @@
-#include <matador/sql/dialect.hpp>
-#include <matador/sql/query_builder.hpp>
-#include <matador/sql/types.hpp>
-
+#include <cstdlib>
 #include <iostream>
-
-using namespace matador;
+#include <string>
 
 int main() {
-  sql::dialect d;
-
-  sql::query_builder query(d);
-
-  std::cout << query.create().table("person", {
-    { "id", sql::data_type_traits<unsigned long>::builtin_type() },
-    { "name", sql::data_type_traits<std::string>::builtin_type(255), 255 },
-    { "id", sql::data_type_traits<unsigned long>::builtin_type() }
-  }).compile();
+  const std::string env_var {"MATADOR_BACKENDS_PATH"};
 
+//  char var[1024];
+//  size_t len{};
+//  const auto error = getenv_s(&len, var, 1024, env_var.c_str());
+//  if (error > 0) {
+//    std::cout << "error: unknown env var " << env_var << "\n";
+//  } else {
+//    std::cout << "env var: " << var << "\n";
+//  }
   return 0;
 }

src/CMakeLists.txt

@@ -9,7 +9,9 @@ set(SQL_SOURCES
   sql/record.cpp
   sql/connection_info.cpp
   sql/connection_impl.cpp
-  sql/session.cpp)
+  sql/session.cpp
+  sql/backend_provider.cpp
+  sql/query_result_impl.cpp)
 
 set(SQL_HEADER
   ../include/matador/sql/dialect.hpp
@@ -27,19 +29,23 @@ set(SQL_HEADER
   ../include/matador/sql/connection_impl.hpp
   ../include/matador/sql/connection_info.hpp
   ../include/matador/sql/connection_pool.hpp
-  ../include/matador/sql/session.hpp)
+  ../include/matador/sql/session.hpp
+  ../include/matador/sql/backend_provider.hpp
+  ../include/matador/sql/query_result_impl.hpp)
 
 set(UTILS_HEADER
   ../include/matador/utils/field_attributes.hpp
   ../include/matador/utils/string.hpp
   ../include/matador/utils/constraints.hpp
-  ../include/matador/utils/library.hpp)
+  ../include/matador/utils/library.hpp
+  ../include/matador/utils/os.hpp)
 
 set(UTILS_SOURCES
   utils/field_attributes.cpp
   utils/string.cpp
   sql/condition.cpp
-  utils/library.cpp)
+  utils/library.cpp
+  utils/os.cpp)
 
 add_library(matador STATIC ${SQL_SOURCES} ${SQL_HEADER} ${UTILS_SOURCES} ${UTILS_HEADER})
 target_include_directories(matador PUBLIC ${PROJECT_SOURCE_DIR}/include)

src/sql/backend_provider.cpp

@@ -0,0 +1,62 @@
+#include "matador/sql/backend_provider.hpp"
+
+#include "matador/utils/os.hpp"
+
+#include <cstdint>
+#include <stdexcept>
+
+namespace matador::sql {
+backend_provider::backend_provider()
+: backends_path_(utils::os::getenv("MATADOR_BACKENDS_PATH"))
+{}
+
+backend_provider &backend_provider::instance() {
+  static backend_provider provider;
+  return provider;
+}
+
+connection_impl *backend_provider::create_connection(const std::string &connection_type, const connection_info &info)
+{
+  auto it = backends_.find(connection_type);
+  if (it == backends_.end()) {
+    it = backends_.emplace(connection_type, std::make_unique<backend_context>(connection_type, backends_path_)).first;
+  }
+  return (*it->second->create_connection)(info);
+}
+
+void backend_provider::destroy_connection(const std::string &connection_type, connection_impl *c)
+{
+  auto it = backends_.find(connection_type);
+  if (it == backends_.end()) {
+    it = backends_.emplace(connection_type, std::make_unique<backend_context>(connection_type, backends_path_)).first;
+  }
+  (*it->second->destroy_connection)(c);
+}
+
+const dialect &backend_provider::connection_dialect(const std::string &connection_type)
+{
+  auto it = backends_.find(connection_type);
+  if (it == backends_.end()) {
+    it = backends_.emplace(connection_type, std::make_unique<backend_context>(connection_type, backends_path_)).first;
+  }
+  return *(*it->second->get_dialect)();
+}
+
+backend_provider::backend_context::backend_context(const std::string &connection_type,
+                                                   const std::string &backends_path)
+{
+  if (!lib.load("matador-" + connection_type)) {
+    throw std::runtime_error("couldn't load library '" + connection_type + "'");
+  }
+
+  create_connection = reinterpret_cast<create_func>(reinterpret_cast<std::uintptr_t>(lib.function("create_database")));
+  destroy_connection = reinterpret_cast<destroy_func>(reinterpret_cast<std::uintptr_t>(lib.function("destroy_database")));
+  get_dialect = reinterpret_cast<dialect_func >(reinterpret_cast<std::uintptr_t>(lib.function("get_dialect")));
+}
+
+backend_provider::backend_context::~backend_context()
+{
+  lib.unload();
+}
+
+}

src/sql/connection.cpp

@@ -1,30 +1,49 @@
-#include <utility>
-
 #include "matador/sql/connection.hpp"
 
+#include "matador/sql/backend_provider.hpp"
+#include "matador/sql/connection_impl.hpp"
+
+#include <utility>
+
 namespace matador::sql {
 
-connection::connection(std::string dns)
-: dns_(std::move(dns)) {}
+connection::connection(connection_info info)
+: connection_info_(std::move(info))
+{
+  connection_ = backend_provider::instance().create_connection(connection_info_.type, connection_info_);
+}
+
+connection::connection(const std::string& dns)
+: connection(connection_info::parse(dns))
+{}
+
+connection::~connection()
+{
+  if (connection_->is_open()) {
+    connection_->close();
+  }
+  backend_provider::instance().destroy_connection(connection_info_.type, connection_);
+  connection_ = nullptr;
+}
 
 void connection::open()
 {
-  is_open_ = true;
+  connection_->open();
 }
 
 void connection::close()
 {
-  is_open_ = false;
+  connection_->close();
 }
 
 bool connection::is_open() const
 {
-  return is_open_;
+  return connection_->is_open();
 }
 
-const std::string &connection::dns() const
+const connection_info &connection::info() const
 {
-  return dns_;
+  return connection_info_;
 }
 
 query_result<record> connection::fetch(const std::string &sql)

src/sql/connection_impl.cpp

@@ -1,11 +1,9 @@
-#include <utility>
-
 #include "matador/sql/connection_impl.hpp"
 
 namespace matador::sql {
 
-connection_impl::connection_impl(connection_info info)
-: info_(std::move(info)){}
+connection_impl::connection_impl(const connection_info &info)
+: info_(info){}
 
 const connection_info &connection_impl::info() const {
   return info_;

src/sql/dialect.cpp

@@ -3,6 +3,26 @@
 #include "matador/utils/string.hpp"
 
 namespace matador::sql {
+
+dialect::dialect(const dialect::token_to_string_map &token_replace_map, const dialect::data_type_to_string_map &data_type_replace_map)
+{
+  for (const auto &token : token_replace_map) {
+    tokens_[token.first] = token.second;
+  }
+
+  for (const auto &data_type : data_type_replace_map) {
+    data_types_[data_type.first] = data_type.second;
+  }
+}
+
+dialect::dialect(const dialect::data_type_to_string_map &data_type_replace_map)
+: dialect({}, data_type_replace_map)
+{}
+
+dialect::dialect(const dialect::token_to_string_map &token_replace_map)
+: dialect(token_replace_map, {})
+{}
+
 const std::string& dialect::token_at(dialect::token_t token) const
 {
   return tokens_.at(token);

src/sql/query_result_impl.cpp

@@ -0,0 +1,25 @@
+#include "matador/sql/query_result_impl.hpp"
+
+namespace matador::sql {
+
+void query_result_impl::on_primary_key(const char *id, std::string &value, size_t size)
+{
+  read_value(id, column_index_++, value, size);
+}
+
+void query_result_impl::on_revision(const char *id, unsigned long long int &rev)
+{
+  read_value(id, column_index_++, rev);
+}
+
+void query_result_impl::on_attribute(const char *id, char *value, const utils::field_attributes &attr)
+{
+  read_value(id, column_index_++, value, attr.size());
+}
+
+void query_result_impl::on_attribute(const char *id, std::string &value, const utils::field_attributes &attr)
+{
+  read_value(id, column_index_++, value, attr.size());
+}
+
+}

src/sql/session.cpp

@@ -1,12 +1,14 @@
 #include "matador/sql/session.hpp"
 
+#include "matador/sql/backend_provider.hpp"
+
 #include <stdexcept>
 
 namespace matador::sql {
 
 session::session(connection_pool<connection> &pool)
 : pool_(pool)
-, query_(dialect_) {}
+, query_(backend_provider::instance().connection_dialect(pool.info().type)) {}
 
 query_create_intermediate session::create()
 {

src/utils/library.cpp

@@ -1,4 +1,5 @@
 #include "matador/utils/library.hpp"
+#include "matador/utils/os.hpp"
 
 namespace matador::utils {
 
@@ -13,16 +14,20 @@ library::~library()
 
 bool library::load()
 {
+  auto path = os::getenv("MATADOR_BACKENDS_PATH");
 #if defined(_MSC_VER) || defined(__MINGW32__)
-  handle_ = LoadLibrary((lib_ + ".dll").c_str());
+  auto cookie = AddDllDirectory(std::wstring(path.begin(), path.end()).c_str());
+  handle_ = LoadLibraryExA((lib_ + ".dll").c_str(), nullptr, LOAD_LIBRARY_SEARCH_DEFAULT_DIRS);
+  RemoveDllDirectory(cookie);
 #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);
+  handle_ = dlopen((path + "/lib" + lib_ + ".so").c_str(), RTLD_LAZY);
 #endif
   if (!handle_) {
 #if defined(_MSC_VER) || defined(__MINGW32__)
     DWORD errorMessageID = ::GetLastError();
+    auto errstr = utils::os::error_string(errorMessageID);
 #else
     // TODO: handle win32 and linux error
     fprintf(stdout, "dlopen error: %s", dlerror());
@@ -61,7 +66,8 @@ bool library::unload()
 func_ptr library::function(const std::string &f) const
 {
 #if defined(_MSC_VER) || defined(__MINGW32__)
-  return GetProcAddress(handle_, f.c_str());
+  auto *addr = GetProcAddress(handle_, f.c_str());
+  return addr;
 #else
   return dlsym(handle_, f.c_str());
 #endif

src/utils/os.cpp

@@ -0,0 +1,48 @@
+#include "matador/utils/os.hpp"
+
+#include <stdexcept>
+
+#ifdef _WIN32
+#include <windows.h>
+#endif
+
+namespace matador::utils::os {
+
+std::string getenv(const char *name) {
+#ifdef _WIN32
+  char var[1024];
+  size_t len{};
+  const auto error = getenv_s(&len, var, 1024, name);
+  if (error > 0) {
+    throw std::logic_error(error_string(error));
+  };
+
+  return var;
+#else
+  return ::getenv(name);
+#endif
+}
+
+[[maybe_unused]] std::string getenv(const std::string &name) {
+  return getenv(name.c_str());
+}
+
+#ifdef _WIN32
+std::string error_string(unsigned long error) {
+  char* lpMsgBuf;
+  auto bufLen = FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+                              nullptr,
+                              error,
+                              MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+                              (LPTSTR) &lpMsgBuf,
+                              0,
+                              nullptr);
+  std::string result;
+  if (bufLen) {
+    result.append(lpMsgBuf, lpMsgBuf+bufLen);
+    LocalFree(lpMsgBuf);
+  }
+  return result;
+}
+#endif
+}

test/CMakeLists.txt

@@ -12,6 +12,11 @@ add_executable(tests builder.cpp
   session.cpp
   record.cpp
   connection_pool.cpp
-  query.cpp)
-target_link_libraries(tests PRIVATE Catch2::Catch2WithMain matador)
+  query.cpp
+  backend_provider.cpp)
+target_link_libraries(tests PRIVATE
+  Catch2::Catch2WithMain
+  matador
+  ${CMAKE_DL_LIBS}
+  ${SQLite3_LIBRARIES})
 target_include_directories(tests PUBLIC $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}>/include)

test/backend_provider.cpp

@@ -0,0 +1,23 @@
+#include <catch2/catch_test_macros.hpp>
+
+#include "matador/sql/connection_info.hpp"
+#include "matador/sql/backend_provider.hpp"
+
+#include "matador/utils/os.hpp"
+
+using namespace matador::sql;
+
+TEST_CASE("Load backend", "[backend provider]") {
+  auto path = matador::utils::os::getenv("MATADOR_BACKENDS_PATH");
+  if (path.back() != '\\') {
+    path.push_back('\\');
+  }
+
+  REQUIRE(!path.empty());
+
+  connection_info ci{};
+  const auto &d = backend_provider::instance().connection_dialect("sqlite");
+  auto *connection = backend_provider::instance().create_connection("sqlite", ci);
+  REQUIRE(connection != nullptr);
+  backend_provider::instance().destroy_connection("sqlite", connection);
+}

test/connection_pool.cpp

@@ -8,7 +8,7 @@ using namespace matador::sql;
 TEST_CASE("Create connection pool", "[connection pool]") {
   using pool_t = connection_pool<connection>;
 
-  pool_t pool("db", 4);
+  pool_t pool("sqlite://sqlite.db", 4);
 
   REQUIRE(pool.size() == 4);
   REQUIRE(pool.idle() == 4);
@@ -17,7 +17,7 @@ TEST_CASE("Create connection pool", "[connection pool]") {
   auto ptr = pool.acquire();
   REQUIRE(ptr.valid());
   REQUIRE(ptr->is_open());
-  REQUIRE(!ptr->dns().empty());
+//  REQUIRE(!ptr->dns().empty());
 
   REQUIRE(pool.idle() == 3);
   REQUIRE(pool.inuse() == 1);
@@ -31,7 +31,7 @@ TEST_CASE("Create connection pool", "[connection pool]") {
     auto ptr2 = pool.acquire();
     REQUIRE(ptr2.valid());
     REQUIRE(ptr2->is_open());
-    REQUIRE(!ptr2->dns().empty());
+//    REQUIRE(!ptr2->dns().empty());
 
     REQUIRE(pool.idle() == 3);
     REQUIRE(pool.inuse() == 1);

test/session.cpp

@@ -7,7 +7,7 @@
 using namespace matador::sql;
 
 TEST_CASE("Execute create table statement", "[connection]") {
-  connection_pool<connection> pool("dns", 4);
+  connection_pool<connection> pool("sqlite://sqlite.db", 4);
   session s(pool);
 
   const auto res = s.create()
@@ -22,7 +22,7 @@ TEST_CASE("Execute create table statement", "[connection]") {
 }
 
 TEST_CASE("Execute drop table statement", "[connection]") {
-  connection_pool<connection> pool("dns", 4);
+  connection_pool<connection> pool("sqlite://sqlite.db", 4);
   session s(pool);
 
   const auto res = s.drop()
@@ -33,7 +33,7 @@ TEST_CASE("Execute drop table statement", "[connection]") {
 }
 
 TEST_CASE("Execute select statement with where clause", "[connection]") {
-  connection_pool<connection> pool("dns", 4);
+  connection_pool<connection> pool("sqlite://sqlite.db", 4);
   session s(pool);
 
   auto res = s.select({"id", "name", "color"})
@@ -45,7 +45,7 @@ TEST_CASE("Execute select statement with where clause", "[connection]") {
 }
 
 TEST_CASE("Execute select statement with order by", "[connection]") {
-  connection_pool<connection> pool("dns", 4);
+  connection_pool<connection> pool("sqlite://sqlite.db", 4);
   session s(pool);
 
   auto res = s.select({"id", "name", "color"})
@@ -58,7 +58,7 @@ TEST_CASE("Execute select statement with order by", "[connection]") {
 }
 
 TEST_CASE("Execute select statement with group by and order by", "[connection]") {
-  connection_pool<connection> pool("dns", 4);
+  connection_pool<connection> pool("sqlite://sqlite.db", 4);
   session s(pool);
 
   auto res = s.select({"id", "name", "color"})
@@ -72,7 +72,7 @@ TEST_CASE("Execute select statement with group by and order by", "[connection]")
 }
 
 TEST_CASE("Execute insert statement", "[connection]") {
-  connection_pool<connection> pool("dns", 4);
+  connection_pool<connection> pool("sqlite://sqlite.db", 4);
   session s(pool);
 
   auto res = s.insert()
@@ -84,7 +84,7 @@ TEST_CASE("Execute insert statement", "[connection]") {
 }
 
 TEST_CASE("Execute update statement", "[connection]") {
-  connection_pool<connection> pool("dns", 4);
+  connection_pool<connection> pool("sqlite://sqlite.db", 4);
   session s(pool);
 
   auto res = s.update("person")
@@ -99,7 +99,7 @@ TEST_CASE("Execute update statement", "[connection]") {
 }
 
 TEST_CASE("Execute delete statement", "[connection]") {
-  connection_pool<connection> pool("dns", 4);
+  connection_pool<connection> pool("sqlite://sqlite.db", 4);
   session s(pool);
 
   auto res = s.remove()