Apache Pig - Cross 运算符
CROSS 运算符计算两个或多个关系的叉积。 本章通过示例解释如何在 Pig Latin 中使用 Cross 运算符。
语法
下面给出的是CROSS运算符的语法。
grunt> Relation3_name = CROSS Relation1_name, Relation2_name;
示例
假设我们在HDFS的/pig_data/目录下有两个文件,分别是customers.txt和orders.txt,如下所示。
customers.txt
1,Ramesh,32,Ahmedabad,2000.00 2,Khilan,25,Delhi,1500.00 3,kaushik,23,Kota,2000.00 4,Chaitali,25,Mumbai,6500.00 5,Hardik,27,Bhopal,8500.00 6,Komal,22,MP,4500.00 7,Muffy,24,Indore,10000.00
orders.txt
102,2009-10-08 00:00:00,3,3000 100,2009-10-08 00:00:00,3,1500 101,2009-11-20 00:00:00,2,1560 103,2008-05-20 00:00:00,4,2060
grunt> customers = LOAD 'hdfs://localhost:9000/pig_data/customers.txt' USING PigStorage(',') as (id:int, name:chararray, age:int, address:chararray, salary:int); grunt> orders = LOAD 'hdfs://localhost:9000/pig_data/orders.txt' USING PigStorage(',') as (oid:int, date:chararray, customer_id:int, amount:int);
现在让我们对这两个关系使用 cross 运算符来获取这两个关系的叉积,如下所示。
grunt> cross_data = CROSS customers, orders;
验证
使用DUMP运算符验证关系cross_data,如下所示。
grunt> Dump cross_data;
输出
它将产生以下输出,显示关系cross_data的内容。
(7,Muffy,24,Indore,10000,103,2008-05-20 00:00:00,4,2060) (7,Muffy,24,Indore,10000,101,2009-11-20 00:00:00,2,1560) (7,Muffy,24,Indore,10000,100,2009-10-08 00:00:00,3,1500) (7,Muffy,24,Indore,10000,102,2009-10-08 00:00:00,3,3000) (6,Komal,22,MP,4500,103,2008-05-20 00:00:00,4,2060) (6,Komal,22,MP,4500,101,2009-11-20 00:00:00,2,1560) (6,Komal,22,MP,4500,100,2009-10-08 00:00:00,3,1500) (6,Komal,22,MP,4500,102,2009-10-08 00:00:00,3,3000) (5,Hardik,27,Bhopal,8500,103,2008-05-20 00:00:00,4,2060) (5,Hardik,27,Bhopal,8500,101,2009-11-20 00:00:00,2,1560) (5,Hardik,27,Bhopal,8500,100,2009-10-08 00:00:00,3,1500) (5,Hardik,27,Bhopal,8500,102,2009-10-08 00:00:00,3,3000) (4,Chaitali,25,Mumbai,6500,103,2008-05-20 00:00:00,4,2060) (4,Chaitali,25,Mumbai,6500,101,2009-20 00:00:00,4,2060) (2,Khilan,25,Delhi,1500,101,2009-11-20 00:00:00,2,1560) (2,Khilan,25,Delhi,1500,100,2009-10-08 00:00:00,3,1500) (2,Khilan,25,Delhi,1500,102,2009-10-08 00:00:00,3,3000) (1,Ramesh,32,Ahmedabad,2000,103,2008-05-20 00:00:00,4,2060) (1,Ramesh,32,Ahmedabad,2000,101,2009-11-20 00:00:00,2,1560) (1,Ramesh,32,Ahmedabad,2000,100,2009-10-08 00:00:00,3,1500) (1,Ramesh,32,Ahmedabad,2000,102,2009-10-08 00:00:00,3,3000)-11-20 00:00:00,2,1560) (4,Chaitali,25,Mumbai,6500,100,2009-10-08 00:00:00,3,1500) (4,Chaitali,25,Mumbai,6500,102,2009-10-08 00:00:00,3,3000) (3,kaushik,23,Kota,2000,103,2008-05-20 00:00:00,4,2060) (3,kaushik,23,Kota,2000,101,2009-11-20 00:00:00,2,1560) (3,kaushik,23,Kota,2000,100,2009-10-08 00:00:00,3,1500) (3,kaushik,23,Kota,2000,102,2009-10-08 00:00:00,3,3000) (2,Khilan,25,Delhi,1500,103,2008-05-20 00:00:00,4,2060) (2,Khilan,25,Delhi,1500,101,2009-11-20 00:00:00,2,1560) (2,Khilan,25,Delhi,1500,100,2009-10-08 00:00:00,3,1500) (2,Khilan,25,Delhi,1500,102,2009-10-08 00:00:00,3,3000) (1,Ramesh,32,Ahmedabad,2000,103,2008-05-20 00:00:00,4,2060) (1,Ramesh,32,Ahmedabad,2000,101,2009-11-20 00:00:00,2,1560) (1,Ramesh,32,Ahmedabad,2000,100,2009-10-08 00:00:00,3,1500) (1,Ramesh,32,Ahmedabad,2000,102,2009-10-08 00:00:00,3,3000)