Apache pig ApachePigJoin返回空关系

当所有这些字段的数据类型都是字符时

cust_filtered包括以下条目——我存储了此关系，这些条目都在该文件中：

cust_joined = JOIN cust_filtered BY (LOW, HIGH, NORMAL), cust_conversion BY (Low, High, Normal);

cust_id           Val1      Val2     Year      Low  High  Normal  Prod-code
1925635222        16.2      61.2     2013      null null  <=6.9   1234548-5
9253821456        16.8      65.8     2014      null null  <7.0    4548567-9

cust_id Val1 Val2年低高正常产品代码
1925635222 16.2 61.2 2013空空空我不知道为什么它不适合你，它适合我。你能粘贴你的猪脚本吗

Low     High   Normal     Cust-Session     Price
null    null    <=6.9      ABC-1234        16.9
null    null    <=7.0      PQR-4567        87.0

cust_filtered=使用PigStorage（“”）加载'cust_filtered.txt'（客户id:long，Val1:float，Val2:float，年份：chararray，低：chararray，高：chararray，正常：chararray，产品代码：chararray）；
cust_conversion=使用PigStorage（“”）加载“cust_conversion.txt”（低：字符，高：字符，正常：字符，cust_会话：字符，价格：浮动）；
cust_JOINTED=按（低、高、正常）过滤的加入cust_，按（低、高、正常）转换的加入cust_；
已加入的转储客户；
输出：
（1925635222,16.2,61.22013，null，null，我假设您的数据中有null，您有实际的pig值
null
，对吗

如果是这样，那么这就是原因，因为清管器内部联接忽略空键：

cust_filtered = LOAD 'cust_filtered.txt' USING PigStorage(' ') AS(cust_id:long,Val1:float,Val2:float,Year:chararray, LOW:chararray, HIGH:chararray, NORMAL:chararray, Prod_code:chararray);
cust_conversion = LOAD 'cust_conversion.txt' USING PigStorage(' ') AS (Low:chararray, High:chararray, Normal:chararray, Cust_Session:chararray, Price:float);
cust_joined = JOIN cust_filtered BY (LOW, HIGH, NORMAL), cust_conversion BY (Low, High, Normal);
DUMP cust_joined;

OUTPUT:
(1925635222,16.2,61.2,2013,null,null,<=6.9,1234548-5,null,null,<=6.9,ABC-1234,16.9)

看

如果这些是带有
“null”
作为值的字符，那么这应该基本上有效，如另一个答案中所述

The JOIN operator always performs an inner join. Inner joins ignore null keys, so it makes sense to filter them out before the join.