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From: Doug Meil <doug.meil@explorysmedical.com>
To: "user@hbase.apache.org" <user@hbase.apache.org>
Subject: Re: Hbase Map/reduce-How to access individual columns of the table?
Thread-Topic: Hbase Map/reduce-How to access individual columns of the table?
Thread-Index: AQHNHIIRKqICWLEqvkWkm8Q7wCIuQpaerdSA
Date: Tue, 17 Apr 2012 12:23:56 +0000
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Hi there-

Have you seen the chapter on MR in the RefGuide?

http://hbase.apache.org/book.html#mapreduce.example

You use the Result instance just like you would from a client program.


On 4/17/12 6:07 AM, "Ram" <rumshenoy@gmail.com> wrote:

> have a table called User with two columns ,one called visitorId and the
>other=20
>called friend which is a list of strings. I want to check whether the
>VisitorId=20
>is in the friendlist. Can anyone direct me as to how to access the table
>columns=20
>in a map function? I'm not able to picture how data is output from a map
>function in hbase. My code is as follows.
>
>ublic class MapReduce {
>
>static class Mapper1 extends TableMapper<ImmutableBytesWritable, Text> {
>
>    private int numRecords =3D 0;
>    private static final IntWritable one =3D new IntWritable(1);
>
>
>    private final IntWritable ONE =3D new IntWritable(1);
>    private Text text =3D new Text();
>    @Override
>    public void map(ImmutableBytesWritable row, Result values, Context
>context)=20
>throws IOException {
>
>        //What should i do here??how do i access the individual columns
>and      =20
>compare?
>        ImmutableBytesWritable userKey =3D new
>ImmutableBytesWritable(row.get(),
>0, Bytes.SIZEOF_INT);
>
>       context.write(userkey,One);
>                 }
>
>            //context.write(text, ONE);
>        } catch (InterruptedException e) {
>            throw new IOException(e);
>        }
>
>    }
>}
>
>
>
>public static void main(String[] args) throws Exception {
>    Configuration conf =3D HBaseConfiguration.create();
>    Job job =3D new Job(conf, "CheckVisitor");
>    job.setJarByClass(MapReduce.class);
>    Scan scan =3D new Scan();
>    Filter f =3D new RowFilter(CompareOp.EQUAL,new
>SubstringComparator("mId2"));
>    scan.setFilter(f);
>    scan.addFamily(Bytes.toBytes("visitor"));
>    scan.addFamily(Bytes.toBytes("friend"));
>    TableMapReduceUtil.initTableMapperJob("User", scan, Mapper1.class,
>ImmutableBytesWritable.class,Text.class, job);
>
>}
>
>