Avoid tuple materialization in update executor.
Avoid tuple materialization in update executor.


Former-commit-id: 1b17b438463bda63b1295e0d46f29e64c5835081
larryxiao/peloton-1,larryxiao/peloton-1,ranxian/peloton,amaliujia/CMUDB-peloton,ranxian/peloton,amaliujia/CMUDB-peloton,larryxiao/peloton,amaliujia/CMUDB-peloton,larryxiao/peloton-1,larryxiao/peloton,omegaga/peloton,omegaga/peloton,omegaga/peloton,larryxiao/peloton,larryxiao/peloton-1,amaliujia/CMUDB-peloton,ranxian/peloton,larryxiao/peloton-1,larryxiao/peloton-1,amaliujia/CMUDB-peloton,ranxian/peloton,amaliujia/CMUDB-peloton,omegaga/peloton,larryxiao/peloton,omegaga/peloton,larryxiao/peloton,ranxian/peloton,ranxian/peloton,omegaga/peloton,amaliujia/CMUDB-peloton,larryxiao/peloton,larryxiao/peloton,omegaga/peloton,larryxiao/peloton-1