message: [sql_lab] Improve performance, only use slow func when needed
diff: @@ -60,12 +60,14 @@ class ParsedQuery:
  logger.debug("Parsing with sqlparse statement: %s", self.sql)
  self._parsed = sqlparse.parse(self.stripped())
  for statement in self._parsed:
  - self.__extract_from_token(statement)
  self._limit = _extract_limit_from_query(statement)
  - self._table_names = self._table_names - self._alias_names
  @property
  def tables(self) -> Set[str]:
  + if not self._table_names:
  + for statement in self._parsed:
  + self.__extract_from_token(statement)
  + self._table_names = self._table_names - self._alias_names
  return self._table_names
  @property
  