Hi all, If you need any kind of ordering in the output you use on the "sort" operator. It was designed for such needs. The fact that different engines produce differently ordered groups is due to each engine specific optimizations. If you ask PIG to re-order the groups you just remove any benefit of those optimization. I would rather keep groups the way it is because I know I could rely on sort if I need and pay its price or have the best speed if I don't need any specific ordering.
My conclusion is : group makes no guarantee by contract, so this is neither a problem nor a bug. It is a misuse of "group" compared to "sort" Regards, Remi -----Message d'origine----- De : Zhang, Liyun [mailto:[email protected]] Envoyé : jeudi 18 décembre 2014 07:38 À : [email protected] Objet : Is there any way to guarantee the sequence of "group" field as the input when using "group" operator in pig Hi all, I met a problem that "group operator has different results in different engines like "spark" and "mapreduce"(PIG-4282<https://issues.apache.org/jira/browse/PIG-4282>). groupdistinct.pig A = load 'input1.txt' as (age:int,gpa:int); B = group A by age; C = foreach B { D = A.gpa; E = distinct D; generate group, MIN(E); }; dump C; input1.txt is: 10 89 20 78 10 68 10 89 20 92 the mapreduce output is: (10,68),(20,78) the spark output is (20,78),(10,68) These two results are different, because the sequence of field 'group' is not same. Is there any way to guarantee the sequence of "group" field as the input when using "group" operator in pig? Best regards Zhang,Liyun _________________________________________________________________________________________________________________________ Ce message et ses pieces jointes peuvent contenir des informations confidentielles ou privilegiees et ne doivent donc pas etre diffuses, exploites ou copies sans autorisation. Si vous avez recu ce message par erreur, veuillez le signaler a l'expediteur et le detruire ainsi que les pieces jointes. Les messages electroniques etant susceptibles d'alteration, Orange decline toute responsabilite si ce message a ete altere, deforme ou falsifie. Merci. This message and its attachments may contain confidential or privileged information that may be protected by law; they should not be distributed, used or copied without authorisation. If you have received this email in error, please notify the sender and delete this message and its attachments. As emails may be altered, Orange is not liable for messages that have been modified, changed or falsified. Thank you.
