Add postgresql support

CMakeLists.txt

@@ -130,6 +130,12 @@ elseif(NOT WITHOUT_SQLITE3)
   find_package(SQLITE3)
 endif()
 
+if(WITH_POSTGRESQL)
+  find_package(PQ REQUIRED)
+elseif(NOT WITHOUT_POSTGRESQL)
+  find_package(PQ)
+endif()
+
 #
 ## Set all the include directories, depending on what libraries are used
 #
@@ -193,6 +199,7 @@ if(SQLITE3_FOUND)
   add_library(database OBJECT ${source_database})
 
   include_directories(database ${SQLITE3_INCLUDE_DIRS})
+  include_directories(database ${PQ_INCLUDE_DIRS})
   set(USE_DATABASE TRUE)
 else()
   add_library(database OBJECT "")
@@ -261,7 +268,9 @@ if(LIBIDN_FOUND)
 endif()
 if(USE_DATABASE)
   target_link_libraries(${PROJECT_NAME} ${SQLITE3_LIBRARIES})
+  target_link_libraries(${PROJECT_NAME} ${PQ_LIBRARIES})
   target_link_libraries(test_suite ${SQLITE3_LIBRARIES})
+  target_link_libraries(test_suite ${PQ_LIBRARIES})
 endif()
 
 # Define a __FILENAME__ macro with the relative path (from the base project directory)

INSTALL.rst

@@ -32,10 +32,12 @@ libiconv_
 libuuid_
  Generate unique IDs
 
-sqlite3_ (option, but highly recommended)
- Provides a way to store various options in a (sqlite3) database. Each user
- of the gateway can store their own values (for example their prefered port,
- or their IRC password). Without this dependency, many interesting features
+sqlite3_
+or
+libpq_
+ Provides a way to store various options in a database. Each user of the
+ gateway can store their own values (for example their prefered port, or
+ their IRC password). Without this dependency, many interesting features
  are missing.
 
 libidn_ (optional, but recommended)
@@ -165,3 +167,4 @@ to use biboumi.
 .. _systemd: https://www.freedesktop.org/wiki/Software/systemd/
 .. _biboumi.1.rst: doc/biboumi.1.rst
 .. _gcrypt: https://www.gnu.org/software/libgcrypt/
+.. _libpq: https://www.postgresql.org/docs/current/static/libpq.html

cmake/Modules/FindPQ.cmake

+# - Find libpq
+# Find the postgresql front end library
+#
+# This module defines the following variables:
+#   PQ_FOUND  -  True if library and include directory are found
+# If set to TRUE, the following are also defined:
+#   PQ_INCLUDE_DIRS  -  The directory where to find the header file
+#   PQ_LIBRARIES  -  Where to find the library file
+#
+# For conveniance, these variables are also set. They have the same values
+# than the variables above.  The user can thus choose his/her prefered way
+# to write them.
+#   PQ_LIBRARY
+#   PQ_INCLUDE_DIR
+#
+# This file is in the public domain
+
+include(FindPkgConfig)
+
+if(NOT PQ_FOUND)
+  pkg_check_modules(PQ libpq)
+endif()
+
+if(NOT PQ_FOUND)
+  find_path(PQ_INCLUDE_DIRS NAMES libpq-fe.h
+      DOC "The libpq include directory")
+
+  find_library(PQ_LIBRARIES NAMES pq
+      DOC "The pq library")
+
+  # Use some standard module to handle the QUIETLY and REQUIRED arguments, and
+  # set PQ_FOUND to TRUE if these two variables are set.
+  include(FindPackageHandleStandardArgs)
+  find_package_handle_standard_args(PQ REQUIRED_VARS PQ_LIBRARIES PQ_INCLUDE_DIRS)
+
+  if(PQ_FOUND)
+    set(PQ_LIBRARY ${PQ_LIBRARIES} CACHE INTERNAL "")
+    set(PQ_INCLUDE_DIR ${PQ_INCLUDE_DIRS} CACHE INTERNAL "")
+    set(PQ_FOUND ${PQ_FOUND} CACHE INTERNAL "")
+  endif()
+endif()
+
+mark_as_advanced(PQ_INCLUDE_DIRS PQ_LIBRARIES)

src/database/column.hpp

@@ -13,5 +13,10 @@ struct Column
     T value{};
 };
 
-struct Id: Column<std::size_t> { static constexpr auto name = "id_";
-                                 static constexpr auto options = "PRIMARY KEY AUTOINCREMENT"; };
+struct Id: Column<std::size_t> {
+    static constexpr std::size_t unset_value = static_cast<std::size_t>(-1);
+    static constexpr auto name = "id_";
+    static constexpr auto options = "PRIMARY KEY";
+
+    Id(): Column<std::size_t>(-1) {}
+};

src/database/count_query.hpp

@@ -2,6 +2,7 @@
 
 #include <database/query.hpp>
 #include <database/table.hpp>
+#include <database/statement.hpp>
 
 #include <string>
 
@@ -15,20 +16,17 @@ struct CountQuery: public Query
       this->body += std::move(name);
     }
 
-    int64_t execute(sqlite3* db)
+    int64_t execute(DatabaseEngine& db)
     {
-      auto statement = this->prepare(db);
+      auto statement = db.prepare(this->body);
       int64_t res = 0;
-      if (sqlite3_step(statement.get()) == SQLITE_ROW)
-        res = sqlite3_column_int64(statement.get(), 0);
+      if (statement->step() != StepResult::Error)
+        res = statement->get_column_int64(0);
       else
         {
           log_error("Count request didn’t return a result");
           return 0;
         }
-      if (sqlite3_step(statement.get()) != SQLITE_DONE)
-        log_warning("Count request returned more than one result.");
-
       return res;
     }
 };

src/database/database.cpp

@@ -7,16 +7,21 @@
 #include <utils/time.hpp>
 
 #include <config/config.hpp>
+#include <database/sqlite3_engine.hpp>
+#include <database/postgresql_engine.hpp>
 
+#include <database/engine.hpp>
 #include <database/index.hpp>
 
+#include <memory>
+
 #include <sqlite3.h>
 
-sqlite3* Database::db;
-Database::MucLogLineTable Database::muc_log_lines("MucLogLine_");
-Database::GlobalOptionsTable Database::global_options("GlobalOptions_");
-Database::IrcServerOptionsTable Database::irc_server_options("IrcServerOptions_");
-Database::IrcChannelOptionsTable Database::irc_channel_options("IrcChannelOptions_");
+std::unique_ptr<DatabaseEngine> Database::db;
+Database::MucLogLineTable Database::muc_log_lines("muclogline_");
+Database::GlobalOptionsTable Database::global_options("globaloptions_");
+Database::IrcServerOptionsTable Database::irc_server_options("ircserveroptions_");
+Database::IrcChannelOptionsTable Database::irc_channel_options("ircchanneloptions_");
 Database::RosterTable Database::roster("roster");
 std::map<Database::CacheKey, Database::EncodingIn::real_type> Database::encoding_in_cache{};
 
@@ -29,27 +34,26 @@ void Database::open(const std::string& filename)
   // Try to open the specified database.
   // Close and replace the previous database pointer if it succeeded. If it did
   // not, just leave things untouched
-  sqlite3* new_db;
-  auto res = sqlite3_open_v2(filename.data(), &new_db, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, nullptr);
-  Database::close();
-  if (res != SQLITE_OK)
-    {
-      log_error("Failed to open database file ", filename, ": ", sqlite3_errmsg(new_db));
-      sqlite3_close(new_db);
-      throw std::runtime_error("");
-    }
-  Database::db = new_db;
-  Database::muc_log_lines.create(Database::db);
-  Database::muc_log_lines.upgrade(Database::db);
-  Database::global_options.create(Database::db);
-  Database::global_options.upgrade(Database::db);
-  Database::irc_server_options.create(Database::db);
-  Database::irc_server_options.upgrade(Database::db);
-  Database::irc_channel_options.create(Database::db);
-  Database::irc_channel_options.upgrade(Database::db);
-  Database::roster.create(Database::db);
-  Database::roster.upgrade(Database::db);
-  create_index<Database::Owner, Database::IrcChanName, Database::IrcServerName>(Database::db, "archive_index", Database::muc_log_lines.get_name());
+  std::unique_ptr<DatabaseEngine> new_db;
+  static const auto psql_prefix = "postgresql://"s;
+  if (filename.substr(0, psql_prefix.size()) == psql_prefix)
+    new_db = PostgresqlEngine::open("dbname="s + filename.substr(psql_prefix.size()));
+  else
+    new_db = Sqlite3Engine::open(filename);
+  if (!new_db)
+    return;
+  Database::db = std::move(new_db);
+  Database::muc_log_lines.create(*Database::db);
+  Database::muc_log_lines.upgrade(*Database::db);
+  Database::global_options.create(*Database::db);
+  Database::global_options.upgrade(*Database::db);
+  Database::irc_server_options.create(*Database::db);
+  Database::irc_server_options.upgrade(*Database::db);
+  Database::irc_channel_options.create(*Database::db);
+  Database::irc_channel_options.upgrade(*Database::db);
+  Database::roster.create(*Database::db);
+  Database::roster.upgrade(*Database::db);
+  create_index<Database::Owner, Database::IrcChanName, Database::IrcServerName>(*Database::db, "archive_index", Database::muc_log_lines.get_name());
 }
 
 
@@ -59,7 +63,7 @@ Database::GlobalOptions Database::get_global_options(const std::string& owner)
   request.where() << Owner{} << "=" << owner;
 
   Database::GlobalOptions options{Database::global_options.get_name()};
-  auto result = request.execute(Database::db);
+  auto result = request.execute(*Database::db);
   if (result.size() == 1)
     options = result.front();
   else
@@ -73,7 +77,7 @@ Database::IrcServerOptions Database::get_irc_server_options(const std::string& o
   request.where() << Owner{} << "=" << owner << " and " << Server{} << "=" << server;
 
   Database::IrcServerOptions options{Database::irc_server_options.get_name()};
-  auto result = request.execute(Database::db);
+  auto result = request.execute(*Database::db);
   if (result.size() == 1)
     options = result.front();
   else
@@ -91,7 +95,7 @@ Database::IrcChannelOptions Database::get_irc_channel_options(const std::string&
           " and " << Server{} << "=" << server <<\
           " and " << Channel{} << "=" << channel;
   Database::IrcChannelOptions options{Database::irc_channel_options.get_name()};
-  auto result = request.execute(Database::db);
+  auto result = request.execute(*Database::db);
   if (result.size() == 1)
     options = result.front();
   else
@@ -186,7 +190,7 @@ std::vector<Database::MucLogLine> Database::get_muc_logs(const std::string& owne
   if (limit >= 0)
     request.limit() << limit;
 
-  auto result = request.execute(Database::db);
+  auto result = request.execute(*Database::db);
 
   return {result.crbegin(), result.crend()};
 }
@@ -207,7 +211,7 @@ void Database::delete_roster_item(const std::string& local, const std::string& r
   query << " WHERE " << Database::RemoteJid{} << "=" << remote << \
            " AND " << Database::LocalJid{} << "=" << local;
 
-  query.execute(Database::db);
+//  query.execute(*Database::db);
 }
 
 bool Database::has_roster_item(const std::string& local, const std::string& remote)
@@ -216,7 +220,7 @@ bool Database::has_roster_item(const std::string& local, const std::string& remo
   query.where() << Database::LocalJid{} << "=" << local << \
         " and " << Database::RemoteJid{} << "=" << remote;
 
-  auto res = query.execute(Database::db);
+  auto res = query.execute(*Database::db);
 
   return !res.empty();
 }
@@ -226,20 +230,19 @@ std::vector<Database::RosterItem> Database::get_contact_list(const std::string&
   auto query = Database::roster.select();
   query.where() << Database::LocalJid{} << "=" << local;
 
-  return query.execute(Database::db);
+  return query.execute(*Database::db);
 }
 
 std::vector<Database::RosterItem> Database::get_full_roster()
 {
   auto query = Database::roster.select();
 
-  return query.execute(Database::db);
+  return query.execute(*Database::db);
 }
 
 void Database::close()
 {
-  sqlite3_close(Database::db);
-  Database::db = nullptr;
+  Database::db.release();
 }
 
 std::string Database::gen_uuid()

src/database/database.hpp

@@ -7,6 +7,8 @@
 #include <database/column.hpp>
 #include <database/count_query.hpp>
 
+#include <database/engine.hpp>
+
 #include <utils/optional_bool.hpp>
 
 #include <chrono>
@@ -25,11 +27,11 @@ class Database
 
   struct Owner: Column<std::string> { static constexpr auto name = "owner_"; };
 
-  struct IrcChanName: Column<std::string> { static constexpr auto name = "ircChanName_"; };
+  struct IrcChanName: Column<std::string> { static constexpr auto name = "ircchanname_"; };
 
   struct Channel: Column<std::string> { static constexpr auto name = "channel_"; };
 
-  struct IrcServerName: Column<std::string> { static constexpr auto name = "ircServerName_"; };
+  struct IrcServerName: Column<std::string> { static constexpr auto name = "ircservername_"; };
 
   struct Server: Column<std::string> { static constexpr auto name = "server_"; };
 
@@ -44,30 +46,30 @@ class Database
   struct Ports: Column<std::string> { static constexpr auto name = "ports_";
     Ports(): Column<std::string>("6667") {} };
 
-  struct TlsPorts: Column<std::string> { static constexpr auto name = "tlsPorts_";
+  struct TlsPorts: Column<std::string> { static constexpr auto name = "tlsports_";
     TlsPorts(): Column<std::string>("6697;6670") {} };
 
   struct Username: Column<std::string> { static constexpr auto name = "username_"; };
 
   struct Realname: Column<std::string> { static constexpr auto name = "realname_"; };
 
-  struct AfterConnectionCommand: Column<std::string> { static constexpr auto name = "afterConnectionCommand_"; };
+  struct AfterConnectionCommand: Column<std::string> { static constexpr auto name = "afterconnectioncommand_"; };
 
-  struct TrustedFingerprint: Column<std::string> { static constexpr auto name = "trustedFingerprint_"; };
+  struct TrustedFingerprint: Column<std::string> { static constexpr auto name = "trustedfingerprint_"; };
 
-  struct EncodingOut: Column<std::string> { static constexpr auto name = "encodingOut_"; };
+  struct EncodingOut: Column<std::string> { static constexpr auto name = "encodingout_"; };
 
-  struct EncodingIn: Column<std::string> { static constexpr auto name = "encodingIn_"; };
+  struct EncodingIn: Column<std::string> { static constexpr auto name = "encodingin_"; };
 
-  struct MaxHistoryLength: Column<int> { static constexpr auto name = "maxHistoryLength_";
+  struct MaxHistoryLength: Column<int> { static constexpr auto name = "maxhistorylength_";
     MaxHistoryLength(): Column<int>(20) {} };
 
-  struct RecordHistory: Column<bool> { static constexpr auto name = "recordHistory_";
+  struct RecordHistory: Column<bool> { static constexpr auto name = "recordhistory_";
     RecordHistory(): Column<bool>(true) {}};
 
-  struct RecordHistoryOptional: Column<OptionalBool> { static constexpr auto name = "recordHistory_"; };
+  struct RecordHistoryOptional: Column<OptionalBool> { static constexpr auto name = "recordhistory_"; };
 
-  struct VerifyCert: Column<bool> { static constexpr auto name = "verifyCert_";
+  struct VerifyCert: Column<bool> { static constexpr auto name = "verifycert_";
     VerifyCert(): Column<bool>(true) {} };
 
   struct Persistent: Column<bool> { static constexpr auto name = "persistent_";
@@ -134,7 +136,7 @@ class Database
   static int64_t count(const TableType& table)
   {
     CountQuery query{table.get_name()};
-    return query.execute(Database::db);
+    return query.execute(*Database::db);
   }
 
   static MucLogLineTable muc_log_lines;
@@ -142,7 +144,7 @@ class Database
   static IrcServerOptionsTable irc_server_options;
   static IrcChannelOptionsTable irc_channel_options;
   static RosterTable roster;
-  static sqlite3* db;
+  static std::unique_ptr<DatabaseEngine> db;
 
   /**
    * Some caches, to avoid doing very frequent query requests for a few options.
@@ -177,6 +179,11 @@ class Database
     Database::encoding_in_cache.clear();
   }
 
+  static auto raw_exec(const std::string& query)
+  {
+    Database::db->raw_exec(query);
+  }
+
  private:
   static std::string gen_uuid();
   static std::map<CacheKey, EncodingIn::real_type> encoding_in_cache;

src/database/engine.hpp

+#pragma once
+
+/**
+ * Interface to provide non-portable behaviour, specific to each
+ * database engine we want to support.
+ *
+ * Everything else (all portable stuf) should go outside of this class.
+ */
+
+#include <database/statement.hpp>
+
+#include <memory>
+#include <string>
+#include <vector>
+#include <tuple>
+#include <set>
+
+class DatabaseEngine
+{
+ public:
+
+  DatabaseEngine() = default;
+
+  DatabaseEngine(const DatabaseEngine&) = delete;
+  DatabaseEngine& operator=(const DatabaseEngine&) = delete;
+  DatabaseEngine(DatabaseEngine&&) = delete;
+  DatabaseEngine& operator=(DatabaseEngine&&) = delete;
+
+  virtual std::set<std::string> get_all_columns_from_table(const std::string& table_name) = 0;
+  virtual std::tuple<bool, std::string> raw_exec(const std::string& query) = 0;
+  virtual std::unique_ptr<Statement> prepare(const std::string& query) = 0;
+  virtual void extract_last_insert_rowid(Statement& statement) = 0;
+  virtual std::string get_returning_id_sql_string(const std::string&)
+  {
+    return {};
+  }
+  virtual std::string id_column_type() = 0;
+
+  int64_t last_inserted_rowid{-1};
+};

src/database/index.hpp

 #pragma once
 
-#include <sqlite3.h>
+#include <database/engine.hpp>
 
 #include <string>
 #include <tuple>
@@ -25,18 +25,14 @@ add_column_name(std::string& out)
 }
 
 template <typename... Columns>
-void create_index(sqlite3* db, const std::string& name, const std::string& table)
+void create_index(DatabaseEngine& db, const std::string& name, const std::string& table)
 {
-  std::string res{"CREATE INDEX IF NOT EXISTS "};
-  res += name + " ON " + table + "(";
-  add_column_name<0, Columns...>(res);
-  res += ")";
+  std::string query{"CREATE INDEX IF NOT EXISTS "};
+  query += name + " ON " + table + "(";
+  add_column_name<0, Columns...>(query);
+  query += ")";
 
-  char* error;
-  const auto result = sqlite3_exec(db, res.data(), nullptr, nullptr, &error);
-  if (result != SQLITE_OK)
-    {
-      log_error("Error executing query: ", error);
-      sqlite3_free(error);
-    }
+  auto result = db.raw_exec(query);
+  if (std::get<0>(result) == false)
+    log_error("Error executing query: ", std::get<1>(result));
 }

src/database/insert_query.hpp

@@ -12,62 +12,63 @@
 
 #include <sqlite3.h>
 
-template <int N, typename ColumnType, typename... T>
-typename std::enable_if<!std::is_same<std::decay_t<ColumnType>, Id>::value, void>::type
-actual_bind(Statement& statement, std::vector<std::string>& params, const std::tuple<T...>&)
+template <std::size_t N=0, typename... T>
+typename std::enable_if<N < sizeof...(T), void>::type
+update_autoincrement_id(std::tuple<T...>& columns, Statement& statement)
 {
-  const auto value = params.front();
-  params.erase(params.begin());
-  if (sqlite3_bind_text(statement.get(), N + 1, value.data(), static_cast<int>(value.size()), SQLITE_TRANSIENT) != SQLITE_OK)
-    log_error("Failed to bind ", value, " to param ", N);
-}
-
-template <int N, typename ColumnType, typename... T>
-typename std::enable_if<std::is_same<std::decay_t<ColumnType>, Id>::value, void>::type
-actual_bind(Statement& statement, std::vector<std::string>&, const std::tuple<T...>& columns)
-{
-  auto&& column = std::get<Id>(columns);
-  if (column.value != 0)
+  using ColumnType = typename std::decay<decltype(std::get<N>(columns))>::type;
+  if (std::is_same<ColumnType, Id>::value)
     {
-      if (sqlite3_bind_int64(statement.get(), N + 1, static_cast<sqlite3_int64>(column.value)) != SQLITE_OK)
-        log_error("Failed to bind ", column.value, " to id.");
+      log_debug("EXTRACTING LAST ID");
+      auto&& column = std::get<Id>(columns);
     }
-  else if (sqlite3_bind_null(statement.get(), N + 1) != SQLITE_OK)
-    log_error("Failed to bind NULL to param ", N);
+  update_autoincrement_id<N+1>(columns, statement);
 }
 
+template <std::size_t N=0, typename... T>
+typename std::enable_if<N == sizeof...(T), void>::type
+update_autoincrement_id(std::tuple<T...>&, Statement& statement)
+{}
+
 struct InsertQuery: public Query
 {
-  InsertQuery(const std::string& name):
-      Query("INSERT OR REPLACE INTO ")
+  template <typename... T>
+  InsertQuery(const std::string& name, const std::tuple<T...>& columns):
+      Query("INSERT INTO ")
   {
     this->body += name;
+    this->insert_col_names(columns);
+    this->insert_values(columns);
   }
 
   template <typename... T>
-  void execute(const std::tuple<T...>& columns, sqlite3* db)
+  void execute(DatabaseEngine& db, std::tuple<T...>& columns)
   {
-    auto statement = this->prepare(db);
-    {
-      this->bind_param(columns, statement);
-      if (sqlite3_step(statement.get()) != SQLITE_DONE)
-        log_error("Failed to execute query: ", sqlite3_errmsg(db));
-    }
+    auto statement = db.prepare(this->body);
+    this->bind_param(columns, *statement);
+
+    if (statement->step() != StepResult::Error)
+      db.extract_last_insert_rowid(*statement);
+    else
+      log_error("Failed to extract the rowid from the last INSERT");
   }
 
   template <int N=0, typename... T>
   typename std::enable_if<N < sizeof...(T), void>::type
-  bind_param(const std::tuple<T...>& columns, Statement& statement)
+  bind_param(const std::tuple<T...>& columns, Statement& statement, int index=1)
   {
-    using ColumnType = typename std::remove_reference<decltype(std::get<N>(columns))>::type;
+    auto&& column = std::get<N>(columns);
+    using ColumnType = std::decay_t<decltype(column)>;
+
+    if (!std::is_same<ColumnType, Id>::value)
+      actual_bind(statement, column.value, index++);
 
-    actual_bind<N, ColumnType>(statement, this->params, columns);
-    this->bind_param<N+1>(columns, statement);
+    this->bind_param<N+1>(columns, statement, index);
   }
 
   template <int N=0, typename... T>
   typename std::enable_if<N == sizeof...(T), void>::type
-  bind_param(const std::tuple<T...>&, Statement&)
+  bind_param(const std::tuple<T...>&, Statement&, int)
   {}
 
   template <typename... T>
@@ -80,18 +81,21 @@ struct InsertQuery: public Query
 
   template <int N=0, typename... T>
   typename std::enable_if<N < sizeof...(T), void>::type
-  insert_value(const std::tuple<T...>& columns)
+  insert_value(const std::tuple<T...>& columns, int index=1)
   {
-    this->body += "?";
-    if (N != sizeof...(T) - 1)
-      this->body += ",";
-    this->body += " ";
-    add_param(*this, std::get<N>(columns));
-    this->insert_value<N+1>(columns);
+    using ColumnType = std::decay_t<decltype(std::get<N>(columns))>;
+
+    if (!std::is_same<ColumnType, Id>::value)
+      {
+        this->body += "$" + std::to_string(index++);
+        if (N != sizeof...(T) - 1)
+          this->body += ", ";
+      }
+    this->insert_value<N+1>(columns, index);
   }
   template <int N=0, typename... T>
   typename std::enable_if<N == sizeof...(T), void>::type
-  insert_value(const std::tuple<T...>&)
+  insert_value(const std::tuple<T...>&, const int)
   { }
 
   template <typename... T>
@@ -99,27 +103,28 @@ struct InsertQuery: public Query
   {
     this->body += " (";
     this->insert_col_name(columns);
-    this->body += ")\n";
+    this->body += ")";
   }
 
   template <int N=0, typename... T>
   typename std::enable_if<N < sizeof...(T), void>::type
   insert_col_name(const std::tuple<T...>& columns)
   {
-    using ColumnType = typename std::remove_reference<decltype(std::get<N>(columns))>::type;
+    using ColumnType = std::decay_t<decltype(std::get<N>(columns))>;
 
-    this->body += ColumnType::name;
+    if (!std::is_same<ColumnType, Id>::value)
+      {
+        this->body += ColumnType::name;
 
-    if (N < (sizeof...(T) - 1))
-      this->body += ", ";
+        if (N < (sizeof...(T) - 1))
+          this->body += ", ";
+      }
 
     this->insert_col_name<N+1>(columns);
   }
+
   template <int N=0, typename... T>
   typename std::enable_if<N == sizeof...(T), void>::type
   insert_col_name(const std::tuple<T...>&)
   {}
-
-
- private:
 };

src/database/postgresql_engine.cpp

+#include <database/postgresql_engine.hpp>
+
+#include <database/postgresql_statement.hpp>
+
+#include <logger/logger.hpp>
+
+PostgresqlEngine::PostgresqlEngine(PGconn*const conn):
+    conn(conn)
+{}
+
+PostgresqlEngine::~PostgresqlEngine()
+{
+  PQfinish(this->conn);
+}
+
+std::unique_ptr<DatabaseEngine> PostgresqlEngine::open(const std::string& conninfo)
+{
+  log_debug("trying to open: ", conninfo);
+  PGconn* con = PQconnectdb(conninfo.data());
+
+  if (!con)
+    {
+      log_error("Failed to allocate a Postgresql connection");
+      throw std::runtime_error("");
+    }
+  const auto status = PQstatus(con);
+  if (status != CONNECTION_OK)
+    {
+      const char* errmsg = PQerrorMessage(con);
+      log_error("Postgresql connection failed: ", errmsg);
+      throw std::runtime_error("failed to open connection.");
+    }
+  return std::make_unique<PostgresqlEngine>(con);
+}
+
+std::set<std::string> PostgresqlEngine::get_all_columns_from_table(const std::string& table_name)
+{
+  const auto query = "SELECT column_name from information_schema.columns where table_name='" + table_name + "'";
+  auto statement = this->prepare(query);
+  std::set<std::string> columns;
+
+  while (statement->step() == StepResult::Row)
+    columns.insert(statement->get_column_text(0));
+
+  log_debug("found ", columns.size(), " columns.");
+  return columns;
+}
+
+std::tuple<bool, std::string> PostgresqlEngine::raw_exec(const std::string& query)
+{
+  log_debug("raw_exec:", query);
+  PGresult* res = PQexec(this->conn, query.data());
+  auto res_status = PQresultStatus(res);
+  if (res_status != PGRES_COMMAND_OK)
+    return std::make_tuple(false, PQresultErrorMessage(res));
+  return std::make_tuple(true, std::string{});
+}
+
+std::unique_ptr<Statement> PostgresqlEngine::prepare(const std::string& query)
+{
+  return std::make_unique<PostgresqlStatement>(query, this->conn);
+}