games = load 'games.txt' using PigStorage('|') as (gameid: int, begin_time: long, end_time:long);

dump games; 
(1,1235000140,1235002457)
(2,1235000377,1235003300)
(3,1235000414,1235056128)
(1,1235000414,1235056128)
(2,1235000377,1235003300)

第一步：计算时差

difference = foreach games generate gameid, end_time - begin_time as time_lapse;

dump difference;
(1,2317)
(2,2923)
(3,55714)
(1,55714)
(2,2923)

第二步：将游戏id上的数据分组

game_group = group difference by gameid;

dump game_group;
(1,{(1,55714),(1,2317)})
(2,{(2,2923),(2,2923)})
(3,{(3,55714)})

第三步：然后是平均值

average = foreach game_group generate group, AVG(difference.time_lapse);

dump average;
(1,29015.5)
(2,2923.0)
(3,55714.0)