Method update_auto_increment

sql/handler.cc:4551–4777

#define AUTO_INC_DEFAULT_NB_MAX ((1 << AUTO_INC_DEFAULT_NB_MAX_BITS) - 1)

int handler::update_auto_increment()
{
  ulonglong nr, nb_reserved_values;
  bool append= FALSE;
  THD *thd= table->in_use;
  struct system_variables *variables= &thd->variables;
  int result=0, tmp;
  DBUG_ENTER("handler::update_auto_increment");

  /*
    next_insert_id is a "cursor" into the reserved interval, it may go greater
    than the interval, but not smaller.
  */
  DBUG_ASSERT(next_insert_id >= auto_inc_interval_for_cur_row.minimum());

  if ((nr= table->next_number_field->val_int()) != 0 ||
      (table->auto_increment_field_not_null &&
       thd->variables.sql_mode & MODE_NO_AUTO_VALUE_ON_ZERO))
  {

    /*
      There could be an error reported because value was truncated
      when strict mode is enabled.
    */
    if (thd->is_error())
      DBUG_RETURN(HA_ERR_AUTOINC_ERANGE);
    /*
      Update next_insert_id if we had already generated a value in this
      statement (case of INSERT VALUES(null),(3763),(null):
      the last NULL needs to insert 3764, not the value of the first NULL plus
      1).
      Ignore negative values.
    */
    if ((longlong) nr > 0 || (table->next_number_field->flags & UNSIGNED_FLAG))
      adjust_next_insert_id_after_explicit_value(nr);
    insert_id_for_cur_row= 0; // didn't generate anything
    DBUG_RETURN(0);
  }

  if (table->versioned())
  {
    Field *end= table->vers_end_field();
    DBUG_ASSERT(end);
    bitmap_set_bit(table->read_set, end->field_index);
    if (!end->is_max())
    {
      if (thd->lex->sql_command == SQLCOM_ALTER_TABLE)
      {
        if (!table->next_number_field->real_maybe_null())
          DBUG_RETURN(HA_ERR_UNSUPPORTED);
        table->next_number_field->set_null();
      }
      DBUG_RETURN(0);
    }
  }

  // ALTER TABLE ... ADD COLUMN ... AUTO_INCREMENT
  if (thd->lex->sql_command == SQLCOM_ALTER_TABLE)