row.hxx

Go to the documentation of this file.

/* Definitions for the pqxx::result class and support classes.
 *
 * pqxx::result represents the set of result rows from a database query.
 *
 * DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/result instead.
 *
 * Copyright (c) 2000-2025, 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_ROW
#define PQXX_H_ROW
 
#if !defined(PQXX_HEADER_PRE)
#  error "Include libpqxx headers as <pqxx/header>, not <pqxx/header.hxx>."
#endif
 
#include "pqxx/except.hxx"
#include "pqxx/field.hxx"
#include "pqxx/result.hxx"
 
#include "pqxx/internal/concat.hxx"
 
namespace pqxx::internal
{
template<typename... T> class result_iter;
} // namespace pqxx::internal
 
 
namespace pqxx
{

class PQXX_LIBEXPORT row
{
public:
  // TODO: Some of these types conflict: class is both iterator and container.
  // TODO: Set iterator nested types using std::iterator_traits.
  using size_type = row_size_type;
  using difference_type = row_difference_type;
  using const_iterator = const_row_iterator;
  using iterator = const_iterator;
  using reference = field;
  using pointer = const_row_iterator;
  using const_reverse_iterator = const_reverse_row_iterator;
  using reverse_iterator = const_reverse_iterator;
 
  row() noexcept = default;
  row(row &&) noexcept = default;
  row(row const &) noexcept = default;
  row &operator=(row const &) noexcept = default;
  row &operator=(row &&) noexcept = default;

  [[nodiscard]] PQXX_PURE bool operator==(row const &) const noexcept;
  [[nodiscard]] bool operator!=(row const &rhs) const noexcept
  {
    return not operator==(rhs);
  }
 
  [[nodiscard]] const_iterator begin() const noexcept;
  [[nodiscard]] const_iterator cbegin() const noexcept;
  [[nodiscard]] const_iterator end() const noexcept;
  [[nodiscard]] const_iterator cend() const noexcept;

  [[nodiscard]] reference front() const noexcept;
  [[nodiscard]] reference back() const noexcept;
 
  [[nodiscard]] const_reverse_row_iterator rbegin() const noexcept;
  [[nodiscard]] const_reverse_row_iterator crbegin() const noexcept;
  [[nodiscard]] const_reverse_row_iterator rend() const noexcept;
  [[nodiscard]] const_reverse_row_iterator crend() const noexcept;
 
  [[nodiscard]] reference operator[](size_type) const noexcept;
  [[nodiscard]] reference operator[](zview col_name) const;
 
  reference at(size_type) const;
  reference at(zview col_name) const;
 
  [[nodiscard]] constexpr size_type size() const noexcept
  {
    return m_end - m_begin;
  }

  [[nodiscard]] constexpr result::size_type rownumber() const noexcept
  {
    return m_index;
  }


  [[nodiscard]] size_type column_number(zview col_name) const;

  [[nodiscard]] oid column_type(size_type) const;

  [[nodiscard]] oid column_type(zview col_name) const
  {
    return column_type(column_number(col_name));
  }

  [[nodiscard]] oid column_table(size_type col_num) const;

  [[nodiscard]] oid column_table(zview col_name) const
  {
    return column_table(column_number(col_name));
  }


  [[nodiscard]] size_type table_column(size_type) const;

  [[nodiscard]] size_type table_column(zview col_name) const
  {
    return table_column(column_number(col_name));
  }
 
  [[nodiscard]] constexpr result::size_type num() const noexcept
  {
    return rownumber();
  }


  template<typename Tuple> void to(Tuple &t) const
  {
    check_size(std::tuple_size_v<Tuple>);
    convert(t);
  }


  template<typename... TYPE> std::tuple<TYPE...> as() const
  {
    check_size(sizeof...(TYPE));
    using seq = std::make_index_sequence<sizeof...(TYPE)>;
    return get_tuple<std::tuple<TYPE...>>(seq{});
  }


  template<typename TUPLE> TUPLE as_tuple() const
  {
    check_size(std::tuple_size_v<TUPLE>);
    using seq = std::make_index_sequence<std::tuple_size_v<TUPLE>>;
    return get_tuple<TUPLE>(seq{});
  }
 
  [[deprecated("Swap iterators, not rows.")]] void swap(row &) noexcept;

  [[deprecated("Row slicing is going away.  File a bug if you need it.")]] row
  slice(size_type sbegin, size_type send) const;

  [[nodiscard, deprecated("Row slicing is going away.")]] PQXX_PURE bool
  empty() const noexcept;
 
protected:
  friend class const_row_iterator;
  friend class result;
  row(result r, result_size_type index, size_type cols) noexcept;

  void check_size(size_type expected) const
  {
    if (size() != expected)
      throw usage_error{internal::concat(
        "Tried to extract ", expected, " field(s) from a row of ", size(),
        ".")};
  }
 
  template<typename... T> friend class pqxx::internal::result_iter;
  template<typename Tuple> void convert(Tuple &t) const
  {
    extract_fields(t, std::make_index_sequence<std::tuple_size_v<Tuple>>{});
  }
 
  friend class field;

  result m_result;


  result::size_type m_index = 0;
 
  // TODO: Remove m_begin and (if possible) m_end when we remove slice().
  size_type m_begin = 0;
  size_type m_end = 0;
 
private:
  template<typename Tuple, std::size_t... indexes>
  void extract_fields(Tuple &t, std::index_sequence<indexes...>) const
  {
    (extract_value<Tuple, indexes>(t), ...);
  }
 
  template<typename Tuple, std::size_t index>
  void extract_value(Tuple &t) const;

  template<typename TUPLE, std::size_t... indexes>
  auto get_tuple(std::index_sequence<indexes...>) const
  {
    return std::make_tuple(get_field<TUPLE, indexes>()...);
  }

  template<typename TUPLE, std::size_t index> auto get_field() const
  {
    return (*this)[index].as<std::tuple_element_t<index, TUPLE>>();
  }
};
 

class PQXX_LIBEXPORT const_row_iterator : public field
{
public:
  using iterator_category = std::random_access_iterator_tag;
  using value_type = field const;
  using pointer = field const *;
  using size_type = row_size_type;
  using difference_type = row_difference_type;
  using reference = field;
 
#include "pqxx/internal/ignore-deprecated-pre.hxx"
  const_row_iterator() noexcept = default;
#include "pqxx/internal/ignore-deprecated-post.hxx"
  const_row_iterator(row const &t, row_size_type c) noexcept :
          field{t.m_result, t.m_index, c}
  {}
  const_row_iterator(field const &F) noexcept : field{F} {}
  const_row_iterator(const_row_iterator const &) noexcept = default;
  const_row_iterator(const_row_iterator &&) noexcept = default;

  [[nodiscard]] constexpr pointer operator->() const noexcept { return this; }
  [[nodiscard]] reference operator*() const noexcept { return {*this}; }

  const_row_iterator &operator=(const_row_iterator const &) noexcept = default;
  const_row_iterator &operator=(const_row_iterator &&) noexcept = default;
 
  const_row_iterator operator++(int) & noexcept;
  const_row_iterator &operator++() noexcept
  {
    ++m_col;
    return *this;
  }
  const_row_iterator operator--(int) & noexcept;
  const_row_iterator &operator--() noexcept
  {
    --m_col;
    return *this;
  }
 
  const_row_iterator &operator+=(difference_type i) noexcept
  {
    m_col = size_type(difference_type(m_col) + i);
    return *this;
  }
  const_row_iterator &operator-=(difference_type i) noexcept
  {
    m_col = size_type(difference_type(m_col) - i);
    return *this;
  }

  [[nodiscard]] constexpr bool
  operator==(const_row_iterator const &i) const noexcept
  {
    return col() == i.col();
  }
  [[nodiscard]] constexpr bool
  operator!=(const_row_iterator const &i) const noexcept
  {
    return col() != i.col();
  }
  [[nodiscard]] constexpr bool
  operator<(const_row_iterator const &i) const noexcept
  {
    return col() < i.col();
  }
  [[nodiscard]] constexpr bool
  operator<=(const_row_iterator const &i) const noexcept
  {
    return col() <= i.col();
  }
  [[nodiscard]] constexpr bool
  operator>(const_row_iterator const &i) const noexcept
  {
    return col() > i.col();
  }
  [[nodiscard]] constexpr bool
  operator>=(const_row_iterator const &i) const noexcept
  {
    return col() >= i.col();
  }

  [[nodiscard]] inline const_row_iterator
  operator+(difference_type) const noexcept;
 
  friend const_row_iterator
  operator+(difference_type, const_row_iterator const &) noexcept;
 
  [[nodiscard]] inline const_row_iterator
  operator-(difference_type) const noexcept;
  [[nodiscard]] inline difference_type
  operator-(const_row_iterator const &) const noexcept;
 
  [[nodiscard]] inline field operator[](difference_type offset) const noexcept
  {
    return *(*this + offset);
  }
};
 

class PQXX_LIBEXPORT const_reverse_row_iterator : private const_row_iterator
{
public:
  using super = const_row_iterator;
  using iterator_type = const_row_iterator;
  using iterator_type::difference_type;
  using iterator_type::iterator_category;
  using iterator_type::pointer;
  using value_type = iterator_type::value_type;
  using reference = iterator_type::reference;
 
  const_reverse_row_iterator() noexcept = default;
  const_reverse_row_iterator(const_reverse_row_iterator const &) noexcept =
    default;
  const_reverse_row_iterator(const_reverse_row_iterator &&) noexcept = default;
 
  explicit const_reverse_row_iterator(super const &rhs) noexcept :
          const_row_iterator{rhs}
  {
    super::operator--();
  }
 
  [[nodiscard]] PQXX_PURE iterator_type base() const noexcept;

  using iterator_type::operator->;
  using iterator_type::operator*;

  const_reverse_row_iterator &
  operator=(const_reverse_row_iterator const &r) noexcept
  {
    iterator_type::operator=(r);
    return *this;
  }
  const_reverse_row_iterator operator++() noexcept
  {
    iterator_type::operator--();
    return *this;
  }
  const_reverse_row_iterator operator++(int) & noexcept;
  const_reverse_row_iterator &operator--() noexcept
  {
    iterator_type::operator++();
    return *this;
  }
  const_reverse_row_iterator operator--(int) &;
  const_reverse_row_iterator &operator+=(difference_type i) noexcept
  {
    iterator_type::operator-=(i);
    return *this;
  }
  const_reverse_row_iterator &operator-=(difference_type i) noexcept
  {
    iterator_type::operator+=(i);
    return *this;
  }

  [[nodiscard]] const_reverse_row_iterator
  operator+(difference_type i) const noexcept
  {
    return const_reverse_row_iterator{base() - i};
  }
  [[nodiscard]] const_reverse_row_iterator
  operator-(difference_type i) noexcept
  {
    return const_reverse_row_iterator{base() + i};
  }
  [[nodiscard]] difference_type
  operator-(const_reverse_row_iterator const &rhs) const noexcept
  {
    return rhs.const_row_iterator::operator-(*this);
  }
  [[nodiscard]] inline field operator[](difference_type offset) const noexcept
  {
    return *(*this + offset);
  }

  [[nodiscard]] bool
  operator==(const_reverse_row_iterator const &rhs) const noexcept
  {
    return iterator_type::operator==(rhs);
  }
  [[nodiscard]] bool
  operator!=(const_reverse_row_iterator const &rhs) const noexcept
  {
    return !operator==(rhs);
  }
 
  [[nodiscard]] constexpr bool
  operator<(const_reverse_row_iterator const &rhs) const noexcept
  {
    return iterator_type::operator>(rhs);
  }
  [[nodiscard]] constexpr bool
  operator<=(const_reverse_row_iterator const &rhs) const noexcept
  {
    return iterator_type::operator>=(rhs);
  }
  [[nodiscard]] constexpr bool
  operator>(const_reverse_row_iterator const &rhs) const noexcept
  {
    return iterator_type::operator<(rhs);
  }
  [[nodiscard]] constexpr bool
  operator>=(const_reverse_row_iterator const &rhs) const noexcept
  {
    return iterator_type::operator<=(rhs);
  }
};
 
 
const_row_iterator
const_row_iterator::operator+(difference_type o) const noexcept
{
  // TODO:: More direct route to home().columns()?
  return {
    row{home(), idx(), home().columns()},
    size_type(difference_type(col()) + o)};
}
 
inline const_row_iterator operator+(
  const_row_iterator::difference_type o, const_row_iterator const &i) noexcept
{
  return i + o;
}
 
inline const_row_iterator
const_row_iterator::operator-(difference_type o) const noexcept
{
  // TODO:: More direct route to home().columns()?
  return {
    row{home(), idx(), home().columns()},
    size_type(difference_type(col()) - o)};
}
 
inline const_row_iterator::difference_type
const_row_iterator::operator-(const_row_iterator const &i) const noexcept
{
  return difference_type(num() - i.num());
}
 
 
template<typename Tuple, std::size_t index>
inline void row::extract_value(Tuple &t) const
{
  using field_type = strip_t<decltype(std::get<index>(t))>;
  field const f{m_result, m_index, index};
  std::get<index>(t) = from_string<field_type>(f);
}
} // namespace pqxx
#endif