Apache Pig illustrate運(yùn)算符

illustrate 運(yùn)算符為你提供了一系列語句的逐步執(zhí)行。

語法

下面給出了illustrate運(yùn)算符的語法。

grunt> illustrate Relation_name;

例

假設(shè)在HDFS中有一個(gè)包含以下內(nèi)容的文件 student_data.txt 。

001,Rajiv,Reddy,9848022337,Hyderabad
002,siddarth,Battacharya,9848022338,Kolkata 
003,Rajesh,Khanna,9848022339,Delhi
004,Preethi,Agarwal,9848022330,Pune 
005,Trupthi,Mohanthy,9848022336,Bhuwaneshwar
006,Archana,Mishra,9848022335,Chennai.

使用LOAD運(yùn)算符將它讀入關(guān)系 student ，如下所示。

grunt> student = LOAD 'hdfs://localhost:9000/pig_data/student_data.txt' USING PigStorage(',')
   as ( id:int, firstname:chararray, lastname:chararray, phone:chararray, city:chararray );

現(xiàn)在，讓我們說明如下所示的名為student的關(guān)系。

grunt> illustrate student;

輸出

在執(zhí)行上面的語句時(shí)，將獲得以下輸出。

grunt> illustrate student;

INFO  org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapOnly$M ap - Aliases
being processed per job phase (AliasName[line,offset]): M: student[1,10] C:  R:
---------------------------------------------------------------------------------------------
|student | id:int | firstname:chararray | lastname:chararray | phone:chararray | city:chararray |
--------------------------------------------------------------------------------------------- 
|        | 002    | siddarth            | Battacharya        | 9848022338      | Kolkata        |
---------------------------------------------------------------------------------------------