How to get the MilliSeconds between two Epoch time values using PIG script

Game_ID | BeginTime | EndTime

1 | 1235000140| 1235002457
2 | 1235000377| 1235003300
3 | 1235000414| 1235056128
1 | 1235000414| 1235056128
2 | 1235000377| 1235003300

Here i would like to get the Milliseconds between two Epoch time fields, BeginTime and EndTime. Then Calculate the Average time for each games.

Solution

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)

Step 1: Calculate the time difference

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

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

Step 2: Group the data on Game_ID

game_group = group difference by gameid;

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

Step 3: Then the Average

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

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