transaction_base.hxx

/* Common code and definitions for the transaction classes.
 *
 * pqxx::transaction_base defines the interface for any abstract class that
 * represents a database transaction.
 *
 * DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/transaction_base instead.
 *
 * Copyright (c) 2000-2021, Jeroen T. Vermeulen.
 *
 * See COPYING for copyright license.  If you did not receive a file called
 * COPYING with this source code, please notify the distributor of this
 * mistake, or contact the author.
 */
#ifndef PQXX_H_TRANSACTION_BASE
#define PQXX_H_TRANSACTION_BASE

#include "pqxx/compiler-public.hxx"
#include "pqxx/internal/compiler-internal-pre.hxx"

#include <string_view>

/* End-user programs need not include this file, unless they define their own
 * transaction classes.  This is not something the typical program should want
 * to do.
 *
 * However, reading this file is worthwhile because it defines the public
 * interface for the available transaction classes such as transaction and
 * nontransaction.
 */

#include "pqxx/connection.hxx"
#include "pqxx/internal/concat.hxx"
#include "pqxx/internal/encoding_group.hxx"
#include "pqxx/isolation.hxx"
#include "pqxx/result.hxx"
#include "pqxx/row.hxx"
#include "pqxx/stream_from.hxx"

namespace pqxx::internal::gate
{
class transaction_subtransaction;
class transaction_sql_cursor;
class transaction_stream_to;
class transaction_transaction_focus;
} // namespace pqxx::internal::gate


namespace pqxx
{
using namespace std::literals;


class transaction_focus;



class PQXX_LIBEXPORT PQXX_NOVTABLE transaction_base
{
public:
  transaction_base() = delete;
  transaction_base(transaction_base const &) = delete;
  transaction_base(transaction_base &&) = delete;
  transaction_base &operator=(transaction_base const &) = delete;
  transaction_base &operator=(transaction_base &&) = delete;

  virtual ~transaction_base() = 0;


  void commit();


  void abort();

  [[nodiscard]] std::string esc(char const text[]) const
  {
    return conn().esc(text);
  }
  [[nodiscard]] std::string esc(char const text[], std::size_t maxlen) const
  {
    return conn().esc(text, maxlen);
  }
  [[nodiscard]] std::string esc(std::string_view text) const
  {
    return conn().esc(text);
  }


  [[nodiscard]] std::string
  esc_raw(unsigned char const data[], std::size_t len) const
  {
    return to_string(std::basic_string_view<std::byte>{
        reinterpret_cast<std::byte const *>(data), len});
  }
  [[nodiscard]] std::string esc_raw(zview) const;


  [[nodiscard]] std::string unesc_raw(zview text) const
  {
    return conn().unesc_raw(text);
  }


  [[nodiscard]] std::string unesc_raw(char const *text) const
  {
    return conn().unesc_raw(text);
  }


  template<typename T> [[nodiscard]] std::string quote(T const &t) const
  {
    return conn().quote(t);
  }

  [[deprecated("Use std::basic_string<std::byte> instead of binarystring.")]]
  std::string quote(binarystring const &t) const
  {
    return conn().quote(t.bytes_view());
  }

  [[deprecated("Use quote(std::basic_string_view<std::byte>).")]]
  std::string
  quote_raw(unsigned char const bin[], std::size_t len) const
  {
    return quote(std::basic_string_view<std::byte>{reinterpret_cast<std::byte const *>(bin), len});
  }

  [[deprecated("Use quote(std::basic_string_view<std::byte>).")]]
  std::string quote_raw(zview bin) const;

  [[nodiscard]] std::string quote_name(std::string_view identifier) const
  {
    return conn().quote_name(identifier);
  }

  [[nodiscard]] std::string
  esc_like(std::string_view bin, char escape_char = '\\') const
  {
    return conn().esc_like(bin, escape_char);
  }



  result
  exec(std::string_view query, std::string_view desc = std::string_view{});


  result exec(
    std::stringstream const &query, std::string_view desc = std::string_view{})
  {
    return exec(query.str(), desc);
  }


  result exec0(zview query, std::string_view desc = std::string_view{})
  {
    return exec_n(0, query, desc);
  }


  row exec1(zview query, std::string_view desc = std::string_view{})
  {
    return exec_n(1, query, desc).front();
  }


  result exec_n(
    result::size_type rows, zview query,
    std::string_view desc = std::string_view{});


  template<typename TYPE>
  TYPE query_value(zview query, std::string_view desc = std::string_view{})
  {
    row const r{exec1(query, desc)};
    if (std::size(r) != 1)
      throw usage_error{internal::concat(
        "Queried single value from result with ", std::size(r), " columns.")};
    return r[0].as<TYPE>();
  }


  template<typename... TYPE> [[nodiscard]] auto stream(std::string_view query)
  {
    // Tricky: std::make_unique() supports constructors but not RVO functions.
    return pqxx::internal::owning_stream_input_iteration<TYPE...>{
      std::unique_ptr<stream_from>{
        new stream_from{stream_from::query(*this, query)}}};
  }

  template<typename... Args> result exec_params(zview query, Args &&...args)
  {
    params pp(args...);
    return internal_exec_params(query, pp.make_c_params());
  }

  // Execute parameterised statement, expect a single-row result.
  template<typename... Args> row exec_params1(zview query, Args &&...args)
  {
    return exec_params_n(1, query, std::forward<Args>(args)...).front();
  }

  // Execute parameterised statement, expect a result with zero rows.
  template<typename... Args> result exec_params0(zview query, Args &&...args)
  {
    return exec_params_n(0, query, std::forward<Args>(args)...);
  }

  // Execute parameterised statement, expect exactly a given number of rows.
  template<typename... Args>
  result exec_params_n(std::size_t rows, zview query, Args &&...args)
  {
    auto const r{exec_params(query, std::forward<Args>(args)...)};
    check_rowcount_params(rows, std::size(r));
    return r;
  }


  template<typename... Args>
  result exec_prepared(zview statement, Args &&...args)
  {
    params pp(args...);
    return internal_exec_prepared(statement, pp.make_c_params());
  }


  template<typename... Args>
  row exec_prepared1(zview statement, Args &&...args)
  {
    return exec_prepared_n(1, statement, std::forward<Args>(args)...).front();
  }


  template<typename... Args>
  result exec_prepared0(zview statement, Args &&...args)
  {
    return exec_prepared_n(0, statement, std::forward<Args>(args)...);
  }


  template<typename... Args>
  result
  exec_prepared_n(result::size_type rows, zview statement, Args &&...args)
  {
    auto const r{exec_prepared(statement, std::forward<Args>(args)...)};
    check_rowcount_prepared(statement, rows, std::size(r));
    return r;
  }


  void process_notice(char const msg[]) const { m_conn.process_notice(msg); }
  void process_notice(zview msg) const { m_conn.process_notice(msg); }

  [[nodiscard]] connection &conn() const { return m_conn; }


  void set_variable(std::string_view var, std::string_view value);


  std::string get_variable(std::string_view);

  [[nodiscard]] std::string_view name() const noexcept { return m_name; }

protected:

  transaction_base(
    connection &c, std::string_view tname,
    std::shared_ptr<std::string> rollback_cmd) :
          m_conn{c}, m_name{tname}, m_rollback_cmd{rollback_cmd}
  {}


  transaction_base(connection &c, std::string_view tname);

  explicit transaction_base(connection &c);

  void register_transaction();

  void close() noexcept;

  virtual void do_commit() = 0;


  virtual void do_abort();

  void set_rollback_cmd(std::shared_ptr<std::string> cmd)
  {
    m_rollback_cmd = cmd;
  }

  result direct_exec(std::string_view, std::string_view desc = ""sv);
  result
  direct_exec(std::shared_ptr<std::string>, std::string_view desc = ""sv);

private:
  enum class status
  {
    active,
    aborted,
    committed,
    in_doubt
  };

  PQXX_PRIVATE void check_pending_error();

  template<typename T> bool parm_is_null(T *p) const noexcept
  {
    return p == nullptr;
  }
  template<typename T> bool parm_is_null(T) const noexcept { return false; }

  result
  internal_exec_prepared(zview statement, internal::c_params const &args);

  result internal_exec_params(zview query, internal::c_params const &args);

  void check_rowcount_prepared(
    zview statement, result::size_type expected_rows,
    result::size_type actual_rows);

  void
  check_rowcount_params(std::size_t expected_rows, std::size_t actual_rows);

  [[nodiscard]] std::string description() const;

  friend class pqxx::internal::gate::transaction_transaction_focus;
  PQXX_PRIVATE void register_focus(transaction_focus *);
  PQXX_PRIVATE void unregister_focus(transaction_focus *) noexcept;
  PQXX_PRIVATE void register_pending_error(zview) noexcept;
  PQXX_PRIVATE void register_pending_error(std::string &&) noexcept;

  connection &m_conn;


  transaction_focus const *m_focus = nullptr;

  status m_status = status::active;
  bool m_registered = false;
  std::string m_name;
  std::string m_pending_error;

  std::shared_ptr<std::string> m_rollback_cmd;

  constexpr static std::string_view s_type_name{"transaction"sv};
};


// TODO: C++20 "Conversion remains valid after underlying result dies" concept?
template<>
std::string_view transaction_base::query_value<std::string_view>(
  zview query, std::string_view desc) = delete;
template<>
zview transaction_base::query_value<zview>(
  zview query, std::string_view desc) = delete;

} // namespace pqxx


namespace pqxx::internal
{
template<pqxx::isolation_level isolation, pqxx::write_policy rw>
extern const zview begin_cmd;

// These are not static members, so "constexpr" does not imply "inline".
template<>
inline constexpr zview begin_cmd<read_committed, write_policy::read_write>{
  "BEGIN"_zv};
template<>
inline constexpr zview begin_cmd<read_committed, write_policy::read_only>{
  "BEGIN READ ONLY"_zv};
template<>
inline constexpr zview begin_cmd<repeatable_read, write_policy::read_write>{
  "BEGIN ISOLATION LEVEL REPEATABLE READ"_zv};
template<>
inline constexpr zview begin_cmd<repeatable_read, write_policy::read_only>{
  "BEGIN ISOLATION LEVEL REPEATABLE READ READ ONLY"_zv};
template<>
inline constexpr zview begin_cmd<serializable, write_policy::read_write>{
  "BEGIN ISOLATION LEVEL SERIALIZABLE"_zv};
template<>
inline constexpr zview begin_cmd<serializable, write_policy::read_only>{
  "BEGIN ISOLATION LEVEL SERIALIZABLE READ ONLY"_zv};
} // namespace pqxx::internal

#include "pqxx/internal/compiler-internal-post.hxx"
#endif