在猪左边填充字符串

Question

我想用0-s填充字符串数据类型字段。有没有办法做到这一点？我需要有固定长度（40）值。

在此先感谢， 千里眼

Answer 1

必须动态地生成基于剩余字符串的长度零的数目，所以我不认为它可能在本地猪。
这在UDF中是非常有可能的。

input.txt中

11111 
222222222 
33 
org.apache.hadoop.util.NativeCodeLoader 
apachepig 

PigScript：

REGISTER leftformat.jar; 

A = LOAD 'input.txt' USING PigStorage() AS(f1:chararray); 
B = FOREACH A GENERATE format.LEFTPAD(f1); 
DUMP B; 

输出：

(0000000000000000000000000000000000011111) 
(0000000000000000000000000000000222222222) 
(0000000000000000000000000000000000000033) 
(0org.apache.hadoop.util.NativeCodeLoader) 
(0000000000000000000000000000000apachepig) 

UDF代码：的下面Java类文件被编译并作为产生leftformat.jar
LEFTPAD.java

package format; 
import java.io.IOException; 
import org.apache.commons.lang.StringUtils; 
import org.apache.pig.EvalFunc; 
import org.apache.pig.data.Tuple; 

public class LEFTPAD extends EvalFunc<String> { 
@Override 
public String exec(Tuple arg) throws IOException { 
     try 
     { 
      String input = (String)arg.get(0); 
      return StringUtils.leftPad(input, 40, "0"); 
     } 
     catch(Exception e) 
     { 
      throw new IOException("Caught exception while processing the input row ", e); 
     } 
    } 
} 

UPDATE：

1.Download 4 jar files from the below link(apache-commons-lang.jar,piggybank.jar, pig-0.11.0.jar and hadoop-common-2.6.0-cdh5.4.5) 
http://www.java2s.com/Code/Jar/a/Downloadapachecommonslangjar.htm 
http://www.java2s.com/Code/Jar/p/Downloadpiggybankjar.htm 
http://www.java2s.com/Code/Jar/p/Downloadpig0110jar.htm 

2. Set all the 3 jar files to your class path 
    >> export CLASSPATH=/tmp/pig-0.11.1.jar:/tmp/piggybank.jar:/tmp/apache-commons-lang.jar 

3. Create directory name format 
    >>mkdir format 

4. Compile your LEFTPAD.java and make sure all the three jars are included in the class path otherwise compilation issue will come 
    >>javac LEFTPAD.java 

5. Move the class file to format folder 
    >>mv LEFTPAD.class format 

6. Create jar file name leftformat.jar 
    >>jar -cf leftformat.jar format/ 

7. jar file will be created, include into your pig script 

Example from command line: 
$ mkdir format 
$ javac LEFTPAD.java 
$ mv LEFTPAD.class format/ 
$ jar -cf leftformat.jar format/ 
$ ls 
LEFTPAD.java format  input.txt leftformat.jar script.pig