piglatin limit and flatten产生错误的结果

b5lpy0ml 于 2021-06-24 发布在 Pig

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B = GROUP A BY state;
C = FOREACH B {                          
   DA = ORDER A BY population DESC;                
   DB = LIMIT DA 5;                         
   GENERATE FLATTEN(group), FLATTEN(DB.name), FLATTEN(DB.population);
}

问题是我得到的城市名称是5次而不是1次。我得到的结果是：

(ALASKA,M,27257)
(ALASKA,M,23696)
(ALASKA,M,19949)
(ALASKA,M,19926)
(ALASKA,M,19833)
(ALASKA,H,27257)
(ALASKA,H,23696)
(ALASKA,H,19949)
(ALASKA,H,19926)
(ALASKA,H,19833)

我需要的结果是：

(ALASKA,M,27257)
(ALASKA,H,23696)

apache-pig Flatten Limit

来源：https://stackoverflow.com/questions/13691123/piglatin-limit-and-flatten-produces-wrong-results

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按热度按时间

bqf10yzr1#

2展平：展平（db.name），展平（db.population）；造成卡特里安产品在两袋之间，用一袋替换

B = GROUP A BY state;
C = FOREACH B {                          
   DA = ORDER A BY population DESC;                
   DB = LIMIT DA 5;                         
   GENERATE FLATTEN(group), FLATTEN(DB.(name, population));
}

或者，由于group by创建的包包含所有原始元组和所有列，因此可以执行以下操作：

B = GROUP A BY state;
C = FOREACH B {                          
   DA = ORDER A BY population DESC;                
   DB = LIMIT DA 5;                         
   GENERATE FLATTEN(DB);
}

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piglatin limit and flatten产生错误的结果

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