Method print_hints

sql/sql_select.cc:32741–32778

}

void st_select_lex::print_hints(THD *thd, String *str)
{
  if (!parent_lex->opt_hints_global)
    return;

  const bool is_view= parent_lex->sql_command == SQLCOM_CREATE_VIEW ||
                      parent_lex->sql_command == SQLCOM_SHOW_CREATE;
  constexpr LEX_CSTRING header={STRING_WITH_LEN("/*+ ")};
  str->append(header);
  const uint32 len_before_hints= str->length();

  if (opt_hints_qb)
    opt_hints_qb->append_qb_hint(thd, str);
  if (this == parent_lex->unit.first_select() && !is_view)
  {
    /*
      For normal queries (not views creation/show) opt_hints_global will
      print itself and all children recursively into the first select.
      Global hints are not supported inside views, so it is safe to skip them
    */
    parent_lex->opt_hints_global->print(thd, str);
  }
  if (is_view && opt_hints_qb)
  {
    // For views print hints related to a QB right into the QB they target
    opt_hints_qb->print(thd, str);
  }

  // If no hints were added, then rollback the previouly added header.
  if (str->length() <= len_before_hints)
  {
    str->length(len_before_hints - header.length);
    return;
  }

  // Some hints were printed, close the hint string
  str->append(STRING_WITH_LEN("*/ "));
}

/**
  Change the select_result object of the JOIN.