filesort.h

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   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.

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   You should have received a copy of the GNU General Public License
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   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */

#ifndef FILESORT_INCLUDED
#define FILESORT_INCLUDED

#include <stddef.h>
#include <sys/types.h>

#include "my_base.h" /* ha_rows */
#include "my_dbug.h"
#include "my_inttypes.h"
#include "sql/sort_param.h"

class Addon_fields;
class Field;
class QEP_TAB;
class RowIterator;
class Sort_result;
class THD;
struct ORDER;
struct TABLE;
struct st_sort_field;

enum class Addon_fields_status;

/**
  Sorting related info.
*/
class Filesort {
 public:
  THD *m_thd;
  /// The QEP entry for the table to be sorted
  QEP_TAB *const qep_tab;
  /// Maximum number of rows to return
  ha_rows limit;
  /// ORDER BY list with some precalculated info for filesort
  st_sort_field *sortorder;
  /// true means we are using Priority Queue for order by with limit.
  bool using_pq;
  /// true means force stable sorting
  bool m_force_stable_sort;
  bool m_remove_duplicates;
  // If true, we will always sort references to rows on table (and crucially,
  // the result iterators used will always position the underlying table on
  // the original row before returning from Read()).
  bool m_force_sort_positions;
  // TODO: Consider moving this into private members of Filesort.
  Sort_param m_sort_param;

  Filesort(THD *thd, QEP_TAB *tab_arg, ORDER *order, ha_rows limit_arg,
           bool force_stable_sort, bool remove_duplicates,
           bool force_sort_positions);

  Addon_fields *get_addon_fields(ulong max_length_for_sort_data,
                                 Field **ptabfield, uint sortlength,
                                 Addon_fields_status *addon_fields_status,
                                 uint *plength, uint *ppackable_length);

  // Number of elements in the sortorder array.
  uint sort_order_length() const { return m_sort_order_length; }

  /// Whether we are using addon fields (sort entire rows) or not (sort row
  /// IDs). Note that on the first call, this actually makes Sort_param
  /// compute the decision and cache it, so it cannot be called before the sort
  /// order is properly set up.
  bool using_addon_fields();

 private:
  /* Prepare ORDER BY list for sorting. */
  uint make_sortorder(ORDER *order);

  uint m_sort_order_length;
};

bool filesort(THD *thd, Filesort *fsort, RowIterator *source_iterator,
              Filesort_info *fs_info, Sort_result *sort_result,
              ha_rows *found_rows);
void filesort_free_buffers(TABLE *table, bool full);
void change_double_for_sort(double nr, uchar *to);

/// Declared here so we can unit test it.
uint sortlength(THD *thd, st_sort_field *sortorder, uint s_length);

#endif /* FILESORT_INCLUDED */