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Date: Sun, 29 Oct 2006 18:16:03 +0800
From: TKDD <mytkdd@gmail.com>
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To: hadoop-user@lucene.apache.org
Subject: Re: how to implement RecordReader.createValue()
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Thank you, my friends,

it really helps


- TKDD


Owen O'Malley wrote:
>
> On Oct 28, 2006, at 8:55 AM, Grant Ingersoll wrote:
>
>> My understanding is that you just construct a new instance of the 
>> Writable that you want as the value, which later gets passed to the 
>> next method.  For instance, just construct, a new Text() object or 
>> something.
>
> Yes, the intent is to have the RecordReader to create an instance of 
> the value type that it wants to read into. Look at the 
> SequenceFileRecordReader. Basically the framework is going to do:
>
> WrtiableComparable key = recordReader.createKey();
> Writable value = recordReader.createValue();
> while (recordReader.next(key, value)) {
>   mapper.map(key, value, collector, reporter);
> }
>
> look at MapRunner.java.
>
> -- Owen
>