presto-main/src/main/java/io/prestosql/sql/analyzer/RelationId.java/RelationId/toString
class RelationId:    @Override
    public String toString()
    {
        if (isAnonymous()) {
            return toStringHelper(this)
                    .addValue("anonymous")
                    .addValue(format("x%08x", identityHashCode(this)))
                    .toString();
        }
        else {
            return toStringHelper(this)
                    .addValue(sourceNode.getClass().getSimpleName())
                    .addValue(format("x%08x", identityHashCode(sourceNode)))
                    .toString();
        }
    }