refactor core workload to reduce redundant key and field generation code
refactor core workload to reduce redundant key and field generation code

madhurihn/YCSB_ToyDB,jaemyoun/YCSB,jaemyoun/YCSB,manolama/YCSB,leschekhomann/YCSB,cricket007/YCSB,jaemyoun/YCSB,manolama/YCSB,ChristianNavolskyi/YCSB,brianfrankcooper/YCSB,zyguan/ycsb,cricket007/YCSB,madhurihn/YCSB_ToyDB,brianfrankcooper/YCSB,cricket007/YCSB,leschekhomann/YCSB,zyguan/ycsb,madhurihn/YCSB_ToyDB,jaemyoun/YCSB,leschekhomann/YCSB,manolama/YCSB,madhurihn/YCSB_ToyDB,brianfrankcooper/YCSB,cricket007/YCSB,ChristianNavolskyi/YCSB,leschekhomann/YCSB,zyguan/ycsb,ChristianNavolskyi/YCSB,zyguan/ycsb,manolama/YCSB,brianfrankcooper/YCSB,ChristianNavolskyi/YCSB