if (hash != null && !hash.startsWith(SIMILAR_DOC_HASH_PREFIX)) {
            try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
                try (GZIPOutputStream gos = new GZIPOutputStream(baos)) {
                    gos.write(hash.getBytes(Constants.UTF_8));
                }

    /**
     * Helper to GZIP-compress a string.
     */
    private byte[] gzipCompress(String text) throws IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try (GZIPOutputStream gos = new GZIPOutputStream(baos)) {
            gos.write(text.getBytes(StandardCharsets.UTF_8));
        }
        return baos.toByteArray();
    }

    /**