presto-main/src/main/java/io/prestosql/type/UuidType.java/UuidType/writeSlice
class UuidType:    @Override
    public void writeSlice(BlockBuilder blockBuilder, Slice value, int offset, int length)
    {
        if (length != INT128_BYTES) {
            throw new IllegalStateException("Expected entry size to be exactly " + INT128_BYTES + " but was " + length);
        }
        blockBuilder.writeLong(value.getLong(offset));
        blockBuilder.writeLong(value.getLong(offset + SIZE_OF_LONG));
        blockBuilder.closeEntry();
    }