#眉標=雲端運算
#副標=開放原始碼的雲端運算平台技術(10)
#大標=Pig實戰–Twitter背後的資料分析機制
#作者=文／圖 沈炳宏


========程式1	<BOX>===============
insert into summary
select ip, count(*)
from app join (
select name, email
from users join clicks on (users.name = clicks.user)
where value > 0;
) using email
group by ip;
========<END>===============



========程式2 <BOX>===============
Users= load 'users' as (name, email);
Clicks= load 'clicks' as (user, url, value);
RealClicks= filter Clicks by value > 0;
UserClicks= join Users by name, RealClicks by user;
summary= foreach UserClicks generate group;
store summary into ‘summary’;
========<END>===============




========程式3	<BOX>===============
public Integer exec(Tuple input) throws
IOException {       
DataBag actions = (DataBag)input.get(0);       
DataBag timestamps = (DataBag)input.get(1);       
if(actions.size() == 0 || timestamps.size() == 0) {           
return null;       
}       
Iterator<Tuple> aIter = actions.iterator();       
Iterator<Tuple> tIter = timestamps.iterator();       
long lastTimestamp = 0;       
int countedSteps = 0;       
while (aIter.hasNext() && tIter.hasNext()) {           
String action = (String)aIter.next().get(0);           
Long timestamp = (Long)tIter.next().get(0);           
if (timestamp > lastTimestamp + sessionTimeout) {        
  countedSteps = 0;            
}           
lastTimestamp = timestamp;           
if (action.equals("purchase")) return countedSteps;           
else countedSteps++;       
}       
return null;
}
========<END>===============




========程式4	<BOX>===============
register SessionAnalysis.jar;
views = load 'views' as (name:chararray, 
timestamp:long, action:chararray, 
purchase:double);
grouped = group views by name parallel 4;
sessions = foreach grouped {      
sorted = order views by timestamp;      
generate group, SessionAnalysis(
sorted.action, sorted.timestamp) as
steps;
}
bysteps = group sessions by steps;
results = foreach bysteps generate group,
COUNT(sessions);
store results into 'results/session';
========<END>===============