replace std multimap with stx btree
replace std multimap with stx btree


Former-commit-id: f746e8f5571d477ca9c586a3544d5a27b786a751
larryxiao/peloton-1,amaliujia/CMUDB-peloton,larryxiao/peloton,omegaga/peloton,larryxiao/peloton-1,ranxian/peloton,omegaga/peloton,larryxiao/peloton-1,larryxiao/peloton-1,omegaga/peloton,omegaga/peloton,amaliujia/CMUDB-peloton,ranxian/peloton,ranxian/peloton,larryxiao/peloton,larryxiao/peloton,amaliujia/CMUDB-peloton,omegaga/peloton,larryxiao/peloton-1,omegaga/peloton,larryxiao/peloton-1,ranxian/peloton,amaliujia/CMUDB-peloton,omegaga/peloton,larryxiao/peloton,larryxiao/peloton,larryxiao/peloton,amaliujia/CMUDB-peloton,ranxian/peloton,amaliujia/CMUDB-peloton,amaliujia/CMUDB-peloton,ranxian/peloton,larryxiao/peloton-1,larryxiao/peloton