Apache Pig Filter运算符

由 jarodhu 创建，youj 最后一次修改 2016-12-28 FILTER 运算符用于根据条件从关系中选择所需的元组。语法下面给出了 FILTER 运算符的语法。grunt> Relation2_name = FILTER Relation1_name BY (condition);例假设在HDFS目录 /pig_data/ 中有一个名为 student_details.txt 的文件，如下所示。 student_details.txt 001,Rajiv,Reddy,21,9848022337,Hyderabad002,siddarth,Battacharya,22,9848022338,Kolkata003,Rajesh,Khanna,22,9848022339,Delhi 004,Preethi,Agarwal,21,9848022330,Pune 005,Trupthi,Mohanthy,23,9848022336,Bhuwaneshwar 006,Archana,Mishra,23,9848022335,Chennai 007,Komal,Nayak,24,9848022334,trivendram 008,Bharathi,Nambiayar,24,9848022333,Chennai将此文件通过关系 student_details 加载到 的Pig中，如下所示。grunt> student_details = LOAD 'hdfs://localhost:9000/pig_data/student_details.txt' USING PigStorage(',') as (id:int, firstname:chararray, lastname:chararray, age:int, phone:chararray, city:chararray);现在使用Filter运算符来获取属于Chennai城市的学生的详细信息。filter_data = FILTER student_details BY city == 'Chennai';验证使用 DUMP 运算符验证关系 filter_data ，如下所示。grunt> Dump filter_data;输出它将产生以下输出，显示关系 filter_data 的内容如下。(6,Archana,Mishra,23,9848022335,Chennai)(8,Bharathi,Nambiayar,24,9848022333,Chennai)