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From "Pete Wyckoff (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4065) support for reading binary data from flat files
Date Mon, 08 Sep 2008 23:57:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12629339#action_12629339
] 

Pete Wyckoff commented on HADOOP-4065:
--------------------------------------

Actual interface

{code:title=TypedSplittableFile.java}

public interface TypedSplittableFile {                                                   
                                                                                         
                           
  public void initialize(FileSystem fileSys, Path path, Configuration conf) throws IOException;
                                                                                         
                     
                                                                                         
                                                                                         
                           
  public Class getKeyClass() ;                                                           
                                                                                         
                           
  public Class getValueClass();                                                          
                                                                                         
                           
                                                                                         
                                                                                         
                           
  public Object next(Object key) throws IOException;                                     
                                                                                         
                           
  public Object getCurrentValue(Object val) throws IOException ;                         
                                                                                         
                           
                                                                                         
                                                                                         
                           
  public boolean syncSeen(); // i.e., atEOF()                                            
                                                                                         
                           
  public void sync(long position) throws IOException; // skip to past last frame boundary
                                                                                         
                           
  public long getPosition() throws IOException;                                          
                                                                                         
                           
  public void seek(long position) throws IOException;                                    
                                                                                         
                           
  public void close() throws IOException;                                                
                                                                                         
                           
                                                                                         
                                                                                         
                           
}    
{code}


> support for reading binary data from flat files
> -----------------------------------------------
>
>                 Key: HADOOP-4065
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4065
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>            Reporter: Joydeep Sen Sarma
>
> like textinputformat - looking for a concrete implementation to read binary records from
a flat file (that may be compressed).
> it's assumed that hadoop can't split such a file. so the inputformat can set splittable
to false.
> tricky aspects are:
> - how to know what class the file contains (has to be in a configuration somewhere).
> - how to determine EOF (would be nice if hadoop can determine EOF and not have the deserializer
throw an exception  (which is hard to distinguish from a exception due to corruptions?)).
this is easy for non-compressed streams - for compressed streams - DecompressorStream has
a useful looking getAvailable() call - except the class is marked package private.

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