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));
                }

     */
    protected byte[] gzipCompress(final byte[] data) {
        try (final ByteArrayOutputStream bos = new ByteArrayOutputStream()) {
            try (final GZIPOutputStream gzipOut = new GZIPOutputStream(bos)) {
                gzipOut.write(data);
            }
            return bos.toByteArray();
        } catch (final IOException e) {
            throw new IORuntimeException(e);
        }

    /**
     * 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();
    }

    /**