Pig: high level language to process big datasets via Hadoop
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Here is a sample program (taken from slide 11) that joins two big datasets (Visits and Pages) to find sessions that end with the "best" page:
Visits = load '/data/visits' as (user, url, time);
Visits = foreach Visits generate user, Canonicalize(url), time;
Pages = load '/data/pages' as (url, pagerank);
VP = join Visits by url, Pages by url;
UserVisits = group VP by user;
Sessions = foreach UserVisits generate FindSessions(*);
HappyEndings = filter Sessions by BestIsLast(*);
store HappyEndings into '/data/happy_endings';
Pig is open-source. It's being "incubated" as an Apache project. More details here:Apache Page: http://incubator.apache.org/pig
Subversion Repository: http://svn.apache.org/repos/asf/incubator/pig
Powerpoint slides: http://www.cs.cmu.edu/~olston/pig.ppt