Hi Alan,

Is the content of the original file ascii text? Then you should be using
<Object, Text, Text, Text> signature. By default 'hadoop fs -text ...' just
will call toString() on the object. You get the object itself in the map()
method and can do whatever you want with it. If Text or BytesWritable does
not work for you, you can always write your own class implementing

Let me know if you need more details how to do this.

Alex K
On Thu, Jul 8, 2010 at 1:59 PM, Alan Miller wrote:

Hi Alex,

I'm not sure what you mean. I already set my mapper's signature to:

public class MyMapper extends Mapper<Object, BytesWritable, Text, Text>
public void map(Text key, BytesWritable value, Context context)

In my map() loop the contents of value is the text from the original file
and the value.toString() returns a String of bytes as hex pairs separated
by space.
But I'd like the original tab separated list of strings (i.e. the lines in
my original files).

I see BytesWritable.getBytes() returns a byte[]. I guess I could write my
RecordReader to convert the byte[] back to text strings but I thought this
something the framework would provide.


On 07/08/2010 08:42 PM, Alex Loddengaard wrote:

Hi Alan,

SequenceFiles keep track of the key and value type, so you should be able
to use the Writables in the signature. Though it looks like you're using
the new API, and I admit that I'm not an expert with the new API. Have you
tried using the Writables in the signature?

On Thu, Jul 8, 2010 at 6:44 AM, Some Body wrote:

To get around the small-file-problem (I have thousands of 2MB log files) I
a class to convert all my log files into a single SequenceFile in
(Text key, BytesWritable value) format. That works fine. I can run this:

hadoop fs -text /my.seq |grep peemt114.log | head -1
10/07/08 15:02:10 INFO util.NativeCodeLoader: Loaded the native-hadoop
10/07/08 15:02:10 INFO zlib.ZlibFactory: Successfully loaded &
initialized native-zlib library
10/07/08 15:02:10 INFO compress.CodecPool: Got brand-new decompressor
peemt114.log 70 65 65 6d 74 31 31 34 09 .........[snip].......

which shows my file name key (peemt114.log)
and file contents value which appears to be converted to hex.
The hex values up to the first tab (09) translate to my hostname.

I'm trying to adapt my mapper to use the SequenceFile as input.

I changed the job's inputFormatClass to:
and modified my mapper signature to:
public class MyMapper extends Mapper<Object, BytesWritable, Text, Text>

but how do I convert the value back to Text? When I print out the
key,values using:
System.out.printf("MAPPER INKEY: [%s]\n", key);
System.out.printf("MAPPER INVAL: [%s]\n", value.toString());
I get::
MAPPER INKEY: [peemt114.log]
MAPPER INVAL: [70 65 65 6d 74 31 31 34 09 .....[snip]......]


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