How to check if it is possible to join on a table before the join in DQL?

Question

SQL

/**
     * @throws JoinIsNotSupportedException
     * @throws ReflectionException
     */
    protected function innerJoinTablesIfNotJoined(
        QueryBuilder $query,
        string $joinToTableName,
        array $checkTablesNamesAliases
    ): QueryBuilder {
        $joinedAliases             = $query->getAllAliases();
        $firstSelectFromTableClass = $query->getRootEntities()[0];
        $paramList                 = $this->getObjectPropertiesNames($firstSelectFromTableClass);
        foreach ($checkTablesNamesAliases as $joinTableAlias) {
            if (false === in_array($joinTableAlias, $paramList, true)) {
                throw  JoinIsNotSupportedException::joinNotSupported($joinToTableName, $joinTableAlias, $paramList);
            }
            if (false === \in_array($joinTableAlias, $joinedAliases, true)) {
                $query->join(\sprintf('%s.%s', $joinToTableName, $joinTableAlias), $joinTableAlias);
            }
        }

        return $query;
    }

The problem is that it $query->getRootEntities()[0];will return only the root entity, the main table from which the selection is made and to which the joins. If we have the 2nd join, for example
Make a selection from table posts -> join -> user -> join -> comments

posts -> join -> userwill work correctly firstSelectFromTableClass === 'posts'
But any level 2+ joy and deeper will already fall.
Maybe you can somehow get the metadata of the fields and their metadata, or check whether there is such a field on pure SQL.

The check is necessary to avoid table joins that don't exist.