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diff --git a/sql/sql_array.h b/sql/sql_array.h
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+++ b/sql/sql_array.h
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+#ifndef SQL_ARRAY_INCLUDED
+#define SQL_ARRAY_INCLUDED
+
+/* Copyright (c) 2003, 2005-2007 MySQL AB, 2009 Sun Microsystems, Inc.
+   Use is subject to license terms.
+   Copyright (c) 2020, MariaDB Corporation.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335  USA */
+
+#include <my_sys.h>
+
+/**
+   A wrapper class which provides array bounds checking.
+   We do *not* own the array, we simply have a pointer to the first element,
+   and a length.
+
+   @remark
+   We want the compiler-generated versions of:
+   - the copy CTOR (memberwise initialization)
+   - the assignment operator (memberwise assignment)
+
+   @param Element_type The type of the elements of the container.
+ */
+template <typename Element_type> class Bounds_checked_array
+{
+public:
+  Bounds_checked_array()= default;
+
+  Bounds_checked_array(Element_type *el, size_t size_arg)
+    : m_array(el), m_size(size_arg)
+  {}
+
+  void reset() { m_array= NULL; m_size= 0; }
+ 
+  void reset(Element_type *array_arg, size_t size_arg)
+  {
+    m_array= array_arg;
+    m_size= size_arg;
+  }
+
+  /**
+    Set a new bound on the array. Does not resize the underlying
+    array, so the new size must be smaller than or equal to the
+    current size.
+   */
+  void resize(size_t new_size)
+  {
+    DBUG_ASSERT(new_size <= m_size);
+    m_size= new_size;
+  }
+
+  Element_type &operator[](size_t n)
+  {
+    DBUG_ASSERT(n < m_size);
+    return m_array[n];
+  }
+
+  const Element_type &operator[](size_t n) const
+  {
+    DBUG_ASSERT(n < m_size);
+    return m_array[n];
+  }
+
+  size_t element_size() const { return sizeof(Element_type); }
+  size_t size() const         { return m_size; }
+
+  bool is_null() const { return m_array == NULL; }
+
+  void pop_front()
+  {
+    DBUG_ASSERT(m_size > 0);
+    m_array+= 1;
+    m_size-= 1;
+  }
+
+  Element_type *array() const { return m_array; }
+
+  Element_type *begin() const { return array(); }
+  Element_type *end() const { return array() + m_size; }
+
+
+  bool operator==(const Bounds_checked_array<Element_type>&rhs) const
+  {
+    return m_array == rhs.m_array && m_size == rhs.m_size;
+  }
+  bool operator!=(const Bounds_checked_array<Element_type>&rhs) const
+  {
+    return m_array != rhs.m_array || m_size != rhs.m_size;
+  }
+
+private:
+  Element_type *m_array= nullptr;
+  size_t        m_size= 0;
+};
+
+/*
+  A typesafe wrapper around DYNAMIC_ARRAY
+
+  TODO: Change creator to take a THREAD_SPECIFIC option.
+*/
+
+template <class Elem> class Dynamic_array
+{
+  DYNAMIC_ARRAY array;
+public:
+  Dynamic_array(PSI_memory_key psi_key, size_t prealloc=16, size_t increment=16)
+  {
+    init(psi_key, prealloc, increment);
+  }
+
+  Dynamic_array(MEM_ROOT *root, size_t prealloc=16, size_t increment=16)
+  {
+    void *init_buffer= alloc_root(root, sizeof(Elem) * prealloc);
+    init_dynamic_array2(root->psi_key, &array, sizeof(Elem), init_buffer,
+                        prealloc, increment, MYF(0));
+  }
+
+  void init(PSI_memory_key psi_key, size_t prealloc=16, size_t increment=16)
+  {
+    init_dynamic_array2(psi_key, &array, sizeof(Elem), 0, prealloc, increment, MYF(0));
+  }
+
+  /**
+     @note Though formally this could be declared "const" it would be
+     misleading at it returns a non-const pointer to array's data.
+  */
+  Elem& at(size_t idx)
+  {
+    DBUG_ASSERT(idx < array.elements);
+    return *(((Elem*)array.buffer) + idx);
+  }
+  /// Const variant of at(), which cannot change data
+  const Elem& at(size_t idx) const
+  {
+    return *(((Elem*)array.buffer) + idx);
+  }
+
+  /// @returns pointer to first element
+  Elem *front()
+  {
+    return (Elem*)array.buffer;
+  }
+
+  /// @returns pointer to first element
+  const Elem *front() const
+  {
+    return (const Elem*)array.buffer;
+  }
+
+  /// @returns pointer to last element
+  Elem *back()
+  {
+    return ((Elem*)array.buffer) + array.elements - 1;
+  }
+
+  /// @returns pointer to last element
+  const Elem *back() const
+  {
+    return ((const Elem*)array.buffer) + array.elements - 1;
+  }
+
+  size_t size() const { return array.elements; }
+
+  const Elem *end() const
+  {
+    return back() + 1;
+  }
+
+  /// @returns pointer to n-th element
+  Elem *get_pos(size_t idx)
+  {
+    return ((Elem*)array.buffer) + idx;
+  }
+
+  /// @returns pointer to n-th element
+  const Elem *get_pos(size_t idx) const
+  {
+    return ((const Elem*)array.buffer) + idx;
+  }
+
+  /**
+     @retval false ok
+     @retval true  OOM, @c my_error() has been called.
+  */
+  bool append(const Elem &el)
+  {
+    return insert_dynamic(&array, &el);
+  }
+
+  bool append_val(Elem el)
+  {
+    return (insert_dynamic(&array, (uchar*)&el));
+  }
+
+  bool push(Elem &el)
+  {
+    return append(el);
+  }
+
+  /// Pops the last element. Does nothing if array is empty.
+  Elem& pop()
+  {
+    return *((Elem*)pop_dynamic(&array));
+  }
+
+  void del(size_t idx)
+  {
+    DBUG_ASSERT(idx <= array.max_element);
+    delete_dynamic_element(&array, idx);
+  }
+
+  size_t elements() const
+  {
+    return array.elements;
+  }
+
+  void elements(size_t num_elements)
+  {
+    DBUG_ASSERT(num_elements <= array.max_element);
+    array.elements= num_elements;
+  }
+
+  void clear()
+  {
+    elements(0);
+  }
+
+  void set(size_t idx, const Elem &el)
+  {
+    set_dynamic(&array, &el, idx);
+  }
+
+  void freeze()
+  {
+    freeze_size(&array);
+  }
+
+  bool reserve(size_t new_size)
+  {
+    return allocate_dynamic(&array, new_size);
+  }
+
+
+  bool resize(size_t new_size, Elem default_val)
+  {
+    size_t old_size= elements();
+    if (reserve(new_size))
+      return true;
+    
+    if (new_size > old_size)
+    {
+      set_dynamic(&array, (uchar*)&default_val, new_size - 1);
+      /*for (size_t i= old_size; i != new_size; i++)
+      {
+        at(i)= default_val;
+      }*/
+    }
+    return false;
+  }
+
+  ~Dynamic_array()
+  {
+    delete_dynamic(&array);
+  }
+
+  void free_memory()
+  {
+    delete_dynamic(&array);
+  }
+
+  typedef int (*CMP_FUNC)(const Elem *el1, const Elem *el2);
+
+  void sort(CMP_FUNC cmp_func)
+  {
+    my_qsort(array.buffer, array.elements, sizeof(Elem), (qsort_cmp)cmp_func);
+  }
+
+  typedef int (*CMP_FUNC2)(void *, const Elem *el1, const Elem *el2);
+  void sort(CMP_FUNC2 cmp_func, void *data)
+  {
+    my_qsort2(array.buffer, array.elements, sizeof(Elem), (qsort2_cmp)cmp_func, data);
+  }
+};
+
+typedef Bounds_checked_array<Item*> Ref_ptr_array;
+
+#endif /* SQL_ARRAY_INCLUDED */