MySQL  8.0.27
Source Code Documentation
visible_fields.h
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23 
24 #ifndef SQL_VISIBLE_FIELDS_H
25 #define SQL_VISIBLE_FIELDS_H
26 
27 /**
28  @file
29  An adapter class to support iteration over an iterator of Item *
30  (typically mem_root_deque<Item *>), while skipping over items that
31  are hidden (item->hidden == true). This is such a common operation
32  that it warrants having its own adapter. You can either do
33 
34  for (Item *item : VisibleFields(fields))
35 
36  or use select->visible_fields().
37 
38  Behavior is undefined if you modify the hidden flag of an item during
39  iteration.
40 
41  TODO(sgunders): When we get C++20, replace with an std::views::filter.
42  */
43 
44 #include "mem_root_deque.h"
45 #include "sql/item.h"
46 
47 template <class Iterator>
49  public:
50  VisibleFieldsAdapter(Iterator base, Iterator end) : m_it(base), m_end(end) {
51  while (m_it != m_end && (*m_it)->hidden) {
52  ++m_it;
53  }
54  }
55 
56  // Pre-increment.
58  do {
59  ++m_it;
60  } while (m_it != m_end && (*m_it)->hidden);
61  return *this;
62  }
63 
64  // Post-increment.
66  VisibleFieldsAdapter ret = *this;
67  do {
68  m_it++;
69  } while (m_it != m_end && (*m_it)->hidden);
70  return ret;
71  }
72 
73  auto &operator*() const { return *m_it; }
74 
75  bool operator==(const VisibleFieldsAdapter &other) const {
76  return m_it == other.m_it;
77  }
78  bool operator!=(const VisibleFieldsAdapter &other) const {
79  return m_it != other.m_it;
80  }
81 
82  private:
83  Iterator m_it, m_end;
84 };
85 
86 template <class Container, class Iterator>
88  public:
89  explicit VisibleFieldsContainer(Container &fields) : m_fields(fields) {}
91  return VisibleFieldsAdapter<Iterator>(m_fields.begin(), m_fields.end());
92  }
95  }
96 
97  private:
98  Container &m_fields;
99 };
100 
101 inline auto VisibleFields(mem_root_deque<Item *> &fields) {
104 }
105 
106 inline auto VisibleFields(const mem_root_deque<Item *> &fields) {
109 }
110 
111 #endif // SQL_VISIBLE_FIELDS_H
Definition: visible_fields.h:48
Iterator m_it
Definition: visible_fields.h:83
VisibleFieldsAdapter & operator++()
Definition: visible_fields.h:57
VisibleFieldsAdapter operator++(int)
Definition: visible_fields.h:65
auto & operator*() const
Definition: visible_fields.h:73
bool operator==(const VisibleFieldsAdapter &other) const
Definition: visible_fields.h:75
bool operator!=(const VisibleFieldsAdapter &other) const
Definition: visible_fields.h:78
Iterator m_end
Definition: visible_fields.h:83
VisibleFieldsAdapter(Iterator base, Iterator end)
Definition: visible_fields.h:50
Definition: visible_fields.h:87
VisibleFieldsContainer(Container &fields)
Definition: visible_fields.h:89
VisibleFieldsAdapter< Iterator > begin()
Definition: visible_fields.h:90
VisibleFieldsAdapter< Iterator > end()
Definition: visible_fields.h:93
Container & m_fields
Definition: visible_fields.h:98
Cursor end()
A past-the-end Cursor.
Definition: rules_table_service.cc:191
auto VisibleFields(mem_root_deque< Item * > &fields)
Definition: visible_fields.h:101