Apache Pig - Storing Data


Advertisements


In the previous chapter, we learnt how to load data into Apache Pig. You can store the loaded data in the file system using the store operator. This chapter explains how to store data in Apache Pig using the Store operator.

Syntax

Given below is the syntax of the Store statement.

STORE Relation_name INTO ' required_directory_path ' [USING function];

Example

Assume we have a file student_data.txt in HDFS with the following content.

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.

And we have read it into a relation student using the LOAD operator as shown below.

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

Now, let us store the relation in the HDFS directory “/pig_Output/” as shown below.

grunt> STORE student INTO ' hdfs://localhost:9000/pig_Output/ ' USING PigStorage (',');

Output

After executing the store statement, you will get the following output. A directory is created with the specified name and the data will be stored in it.

2015-10-05 13:05:05,429 [main] INFO  org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.
MapReduceLau ncher - 100% complete
2015-10-05 13:05:05,429 [main] INFO  org.apache.pig.tools.pigstats.mapreduce.SimplePigStats - 
Script Statistics:
   
HadoopVersion    PigVersion    UserId    StartedAt             FinishedAt             Features 
2.6.0            0.15.0        Hadoop    2015-10-0 13:03:03    2015-10-05 13:05:05    UNKNOWN  
Success!  
Job Stats (time in seconds): 
JobId          Maps    Reduces    MaxMapTime    MinMapTime    AvgMapTime    MedianMapTime    
job_14459_06    1        0           n/a           n/a           n/a           n/a
MaxReduceTime    MinReduceTime    AvgReduceTime    MedianReducetime    Alias    Feature   
     0                 0                0                0             student  MAP_ONLY 
OutPut folder
hdfs://localhost:9000/pig_Output/ 
 
Input(s): Successfully read 0 records from: "hdfs://localhost:9000/pig_data/student_data.txt"  
Output(s): Successfully stored 0 records in: "hdfs://localhost:9000/pig_Output"  
Counters:
Total records written : 0
Total bytes written : 0
Spillable Memory Manager spill count : 0 
Total bags proactively spilled: 0
Total records proactively spilled: 0
  
Job DAG: job_1443519499159_0006
  
2015-10-05 13:06:06,192 [main] INFO  org.apache.pig.backend.hadoop.executionengine
.mapReduceLayer.MapReduceLau ncher - Success!

Verification

You can verify the stored data as shown below.

Step 1

First of all, list out the files in the directory named pig_output using the ls command as shown below.

hdfs dfs -ls 'hdfs://localhost:9000/pig_Output/'
Found 2 items
rw-r--r-   1 Hadoop supergroup          0 2015-10-05 13:03 hdfs://localhost:9000/pig_Output/_SUCCESS
rw-r--r-   1 Hadoop supergroup        224 2015-10-05 13:03 hdfs://localhost:9000/pig_Output/part-m-00000

You can observe that two files were created after executing the store statement.

Step 2

Using cat command, list the contents of the file named part-m-00000 as shown below.

$ hdfs dfs -cat 'hdfs://localhost:9000/pig_Output/part-m-00000' 
1,Rajiv,Reddy,9848022337,Hyderabad
2,siddarth,Battacharya,9848022338,Kolkata
3,Rajesh,Khanna,9848022339,Delhi
4,Preethi,Agarwal,9848022330,Pune
5,Trupthi,Mohanthy,9848022336,Bhuwaneshwar
6,Archana,Mishra,9848022335,Chennai 


Advertisements
E-Books Store