Add function mapping for timestamp operators and sum aggregate function
Add function mapping for timestamp operators and sum aggregate function


Former-commit-id: 240a442c878ebf3bc9c8cbb78549efe41e2cd743
larryxiao/peloton-1,larryxiao/peloton,omegaga/peloton,larryxiao/peloton-1,amaliujia/CMUDB-peloton,larryxiao/peloton,larryxiao/peloton-1,amaliujia/CMUDB-peloton,ranxian/peloton,larryxiao/peloton,amaliujia/CMUDB-peloton,omegaga/peloton,omegaga/peloton,amaliujia/CMUDB-peloton,larryxiao/peloton-1,larryxiao/peloton-1,omegaga/peloton,ranxian/peloton,ranxian/peloton,amaliujia/CMUDB-peloton,larryxiao/peloton-1,larryxiao/peloton,larryxiao/peloton-1,amaliujia/CMUDB-peloton,omegaga/peloton,larryxiao/peloton,omegaga/peloton,omegaga/peloton,larryxiao/peloton,ranxian/peloton,larryxiao/peloton,ranxian/peloton,ranxian/peloton,amaliujia/CMUDB-peloton