public boolean exists(final Txn<ByteBuffer> txn, final ByteBuffer keyBuffer) {
        // It is debatable whether it is cheaper to use a cursor to see if
        // the key exists or a get like this.
        return lmdbDbi.get(txn, keyBuffer) != null;
    }
@return True if any entry exists with a key matching the passed keyBuffer
stroom-lmdb/src/main/java/stroom/lmdb/AbstractLmdbDb.java