added postgres backend

backends/postgres/src/postgres_connection.cpp

@@ -0,0 +1,84 @@
+#include "postgres_connection.hpp"
+#include "postgres_error.hpp"
+
+namespace matador::backends::postgres {
+
+postgres_connection::postgres_connection(const sql::connection_info &info)
+: connection_impl(info) {}
+
+void postgres_connection::open()
+{
+  if (is_open()) {
+    return;
+  }
+
+  std::string connection("user=" + info().user + " password=" + info().password + " host=" + info().hostname + " dbname=" + info().database + " port=" + std::to_string(info().port));
+
+  conn_ = PQconnectdb(connection.c_str());
+  if (PQstatus(conn_) == CONNECTION_BAD) {
+    const auto msg = PQerrorMessage(conn_);
+    PQfinish(conn_);
+    throw_postgres_error(msg, "postgres");
+  }
+}
+
+void postgres_connection::close()
+{
+  if (conn_) {
+    PQfinish(conn_);
+    conn_ = nullptr;
+  }
+}
+
+bool postgres_connection::is_open()
+{
+  return conn_ != nullptr;
+}
+
+std::unique_ptr<sql::query_result_impl> postgres_connection::fetch(const std::string &stmt)
+{
+  PGresult *res = PQexec(conn_, stmt.c_str());
+
+  throw_postgres_error(res, conn_, "postgres", stmt);
+
+  return {};
+}
+
+void postgres_connection::prepare(const std::string &stmt)
+{
+
+}
+
+size_t postgres_connection::execute(const std::string &stmt)
+{
+  PGresult *res = PQexec(conn_, stmt.c_str());
+
+  throw_postgres_error(res, conn_, "postgres", stmt);
+
+  return 0;
+}
+
+sql::record postgres_connection::describe(const std::string &table)
+{
+  return {};
+}
+
+bool postgres_connection::exists(const std::string &table_name)
+{
+  return false;
+}
+
+}
+
+extern "C"
+{
+MATADOR_POSTGRES_API matador::sql::connection_impl *create_database(const matador::sql::connection_info &info)
+{
+  return new matador::backends::postgres::postgres_connection(info);
+}
+
+MATADOR_POSTGRES_API void destroy_database(matador::sql::connection_impl *db)
+{
+  delete db;
+}
+}