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From "Tom White (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3566) Create an InputFormat for reading lines of text as Java Strings
Date Mon, 16 Jun 2008 14:27:46 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3566?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12605300#action_12605300
] 

Tom White commented on HADOOP-3566:
-----------------------------------

I propose a subclass of RecordReader that supports retrieval of the current key and value:

{code}
public interface NewInstanceRecordReader<K, V> extends RecordReader<K, V> {
  
  K getCurrentKey();
  
  V getCurrentValue();
}
{code}

With this change, the framework would need only changes to MapTask to have two types of TrackedRecordReader,
and MapRunner to check the type of RecordRunner and retrieve the current key and value, if
necessary.

Longer term, in HADOOP-1230, we could simply add these new methods to the new RecordReader
interface (which will be in a new package, org.apache.hadoop.mapreduce).

Thoughts?

> Create an InputFormat for reading lines of text as Java Strings
> ---------------------------------------------------------------
>
>                 Key: HADOOP-3566
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3566
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Tom White
>            Assignee: Tom White
>
> Such a StringInputFormat would be like TextInputFormat but with input types of Long and
String, rather than LongWritable and Text. This would allow users to write MapReduce programs
that used only Java native types (i.e. no Writables).
> This is currently not possible to write without changes to Hadoop due to a limitation
in the RecordReader interface explained here: https://issues.apache.org/jira/browse/HADOOP-3413?focusedCommentId=12597935#action_12597935

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