Method parse_optimizer_hints

sql/sql_lex.cc:13982–14016

Parse optimizer hints and return as Hint_list allocated on thd->mem_root. The caller should check both parts of the return value to know what happened, as follows: Retval.first Retval.second Meaning ------------ --------------- ------- false != nullptr the hints were parsed without errors true != nullptr impossible combination false =

  true           == nullptr       fatal error, such as EOM
*/
std::pair<bool, Optimizer_hint_parser_output *>
LEX::parse_optimizer_hints(const Lex_comment_st &hints_str)
{
  DBUG_ASSERT(!hints_str.str || hints_str.length >= 5);
  if (!hints_str.str)
    return {false, nullptr}; // There were no a hint comment

  //  Instantiate the query hint parser.
  //  Remove the leading '/*+' and trailing '*/'
  //  when passing hints to the parser.
  Optimizer_hint_parser p(thd, thd->charset(),
                          Lex_cstring(hints_str.str + 3, hints_str.length - 5));
  // Parse hints
  Optimizer_hint_parser_output hints(&p);
  DBUG_ASSERT(!p.is_error() || !hints);

  if (p.is_fatal_error())
  {
    /*
      Fatal error (e.g. EOM), have the caller fail.
      The SQL error should be in DA already.
    */
    DBUG_ASSERT(thd->is_error());
    return {true, nullptr}; // Set the flag of fatal error
  }

  if (!hints) // Hint parsing failed with a syntax error
  {
    p.push_warning_syntax_error(thd, hints_str.lineno);
    return {false, nullptr}; // Continue and ignore hints.
  }

  // Hints were not empty and were parsed without errors
  return {false, new (thd->mem_root) Optimizer_hint_parser_output(std::move(hints))};
}


/*