code: @Override
    void writeJournal(OutputStream os, 
                      byte[] buffer, int offset,
                      BlobOutputStream blob)
      throws IOException
    {
      if (blob == null) {
        BitsUtil.writeInt16(os, 0);
        return;
      }
  
      if (blob.isLargeBlob()) {
        blob.flushBlob();
        
        BitsUtil.writeInt16(os, LARGE_BLOB_MASK | 4);
        BitsUtil.writeInt(os, blob.getBlobId());
        return;
      }
      
      int len = blob.getSize();
      
      if (len >= 32 * 1024) {
        throw new IllegalStateException("TOO_BIG: " + len);
      }
      
      BitsUtil.writeInt16(os, len);
      
      blob.writeToStream(os);
    }
docs: Writes the blob column to the journal. Large blobs are written to the
  page store and the reference is written to the journal.