presto-main/src/main/java/io/prestosql/server/protocol/Slug.java/Slug/makeSlug
class Slug:    public String makeSlug(Context context, long token)
    {
        // "y" is an arbitrary prefix distinguishing this slug version. Added for troubleshooting purposes.
        return "y" + hmac.newHasher()
                .putInt(requireNonNull(context, "context is null").ordinal())
                .putLong(token)
                .hash()
                .toString();
    }