uniques.h

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#ifndef UNIQUES_INCLUDED
#define UNIQUES_INCLUDED
 
#include <stddef.h>
#include <sys/types.h>
 
#include "my_dbug.h"
#include "my_inttypes.h"
#include "my_pointer_arithmetic.h"
#include "my_sys.h"
#include "my_tree.h"           // TREE
#include "prealloced_array.h"  // Prealloced_array
#include "sql/sql_array.h"
#include "sql/sql_sort.h"  // IWYU pragma: keep
 
class Cost_model_table;
struct TABLE;
 
/**
   Unique -- class for unique (removing of duplicates).
   Puts all values to the TREE. If the tree becomes too big,
   it's dumped to the file. User can request sorted values, or
   just iterate through them. In the last case tree merging is performed in
   memory simultaneously with iteration, so it should be ~2-3x faster.
 
   Unique values can be read only from final result (not on insert) because
   duplicate values can be contained in different dumped tree files.
*/
 
class Unique {
  /// Array of file pointers
  Prealloced_array<Merge_chunk, 16> file_ptrs;
  /// Max elements in memory buffer
  ulong max_elements;
  /// Memory buffer size
  ulonglong max_in_memory_size;
  /// Cache file for unique values retrieval of table read AM in executor
  IO_CACHE file;
  /// Tree to filter duplicates in memory
  TREE tree;
  uchar *record_pointers;
  /// Flush tree to disk
  bool flush();
  /// Element size
  uint size;
 
 public:
  ulong elements;
  Unique(qsort2_cmp comp_func, void *comp_func_fixed_arg, uint size_arg,
         ulonglong max_in_memory_size_arg);
  ~Unique();
  ulong elements_in_tree() { return tree.elements_in_tree; }
 
  /**
    Add new value to Unique
 
    @details The value is inserted either to the tree, or to the duplicate
    weedout table, depending on the mode of operation. If tree's mem buffer is
    full, it's flushed to the disk.
 
    @param ptr  pointer to the binary string to insert
 
    @returns
      false  error or duplicate
      true   the value was inserted
  */
  inline bool unique_add(void *ptr) {
    DBUG_TRACE;
    DBUG_PRINT("info", ("tree %u - %lu", tree.elements_in_tree, max_elements));
    if (tree.elements_in_tree > max_elements && flush()) return true;
    return !tree_insert(&tree, ptr, 0, tree.custom_arg);
  }
 
  bool get(TABLE *table);
 
  static double get_use_cost(uint nkeys, uint key_size,
                             ulonglong max_in_memory_size,
                             const Cost_model_table *cost_model);
 
  void reset();
  bool walk(tree_walk_action action, void *walk_action_arg);
 
  uint get_size() const { return size; }
  ulonglong get_max_in_memory_size() const { return max_in_memory_size; }
  bool is_in_memory() { return elements == 0; }
  friend int unique_write_to_file(void *v_key, element_count count,
                                  void *unique);
  friend int unique_write_to_ptrs(void *v_key, element_count count,
                                  void *unique);
};
 
/**
  Unique_on_insert -- similar to above, but rejects duplicates on insert, not
  just on read of the final result.
  To achieve this values are inserted into mem tmp table which uses index to
  detect duplicate keys. When memory buffer is full, tmp table is dumped to a
  disk-based tmp table.
*/
 
class Unique_on_insert {
  /// Element size
  uint m_size;
  /// Duplicate weedout tmp table
  TABLE *m_table{nullptr};
 
 public:
  Unique_on_insert(uint size) : m_size(size) {}
  /**
    Add row id to the filter
 
    @param ptr pointer to the rowid
 
    @returns
      false  rowid successfully inserted
      true   duplicate or error
  */
  bool unique_add(void *ptr);
 
  /**
    Initialize duplicate filter - allocate duplicate weedout tmp table
 
    @returns
      false initialization succeeded
      true  an error occur
  */
  bool init();
 
  /**
    Reset filter - drop all rowid records
 
    @param reinit  Whether to restart index scan
  */
  void reset(bool reinit);
 
  /**
    Cleanup unique filter
  */
  void cleanup();
};
 
#endif  // UNIQUES_INCLUDED