如何在HBase中选择一部分行并创建一个新表？

Question

我在HBase中有一张大桌子，我想将它们分成几个小桌子，这样我就可以更容易地使用。 （应保留原表。）我该怎么做？

例如：我有一个表，称为all具有以下rowkey：

animal-1, ... 
plant-1, ... 
animal-2, ... 
plant-2, ... 
human-1, ... 
human-2, ... 

我想单独给三个表：animal，plant，human三个类型众生。我该怎么做？

Answer 1

可以像下面的例子一样使用Mapreduce和MultipleTableOutputFormat。

但在下面的例子中，我从文件即TextInputFormat阅读相反，你必须使用TableInputFormat'all'，而不是表1表2从HBase的表中读取它...你必须使用'animal', 'planet', 'human'

根据您的要求，如果您在Hbase表上扫描并使用表格InputFormat将其传递给Mapper，则您还将获得rowkey以及Mapper的映射方法。这需要比较以决定要插入哪个表。

Please see 7.2.2. HBase MapReduce Read/Write Example

package mapred; 
import java.io.IOException; 
import org.apache.hadoop.hbase.io.ImmutableBytesWritable; 
import org.apache.hadoop.hbase.mapreduce.MultiTableOutputFormat; 
import org.apache.hadoop.hbase.util.Bytes; 
import org.apache.hadoop.io.LongWritable; 
import org.apache.hadoop.io.Text; 
import org.apache.hadoop.conf.Configuration; 
import org.apache.hadoop.fs.Path; 
import org.apache.hadoop.mapreduce.Job; 
import org.apache.hadoop.mapreduce.Mapper; 
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; 
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat; 
import org.apache.hadoop.hbase.client.Put; 
public class MultiTableMapper { 
static class InnerMapper extends Mapper <LongWritable, Text, ImmutableBytesWritable, Put> { 
public void map(LongWritable offset, Text value, Context context) throws IOException { 
// contains the line of tab separated data we are working on (needs to be parsed out). 
//byte[] lineBytes = value.getBytes(); 
String valuestring[]=value.toString().split(“\t”); 
String rowid = /*HBaseManager.generateID();*/ “12345”; 
// rowKey is the hbase rowKey generated from lineBytes 
Put put = new Put(rowid.getBytes()); 
put.add(Bytes.toBytes(“UserInfo”), Bytes.toBytes(“StudentName”), Bytes.toBytes(valuestring[0])); 
try { 
context.write(new ImmutableBytesWritable(Bytes.toBytes(“Table1”)), put); 
} catch (InterruptedException e) { 
// TODO Auto-generated catch block 
e.printStackTrace(); 
} // write to the actions table 
// rowKey2 is the hbase rowKey 
Put put1 = new Put(rowid.getBytes()); 
put1.add(Bytes.toBytes(“MarksInfo”),Bytes.toBytes(“Marks”),Bytes.toBytes(valuestring[1])); 
// Create your KeyValue object 
//put.add(kv); 
try { 
context.write(new ImmutableBytesWritable(Bytes.toBytes(“Table2”)), put1); 
} catch (InterruptedException e) { 
// TODO Auto-generated catch block 
e.printStackTrace(); 
} // write to the actions table 
} 
} 
public static void createSubmittableJob() throws IOException, ClassNotFoundException, InterruptedException { 
Path inputDir = new Path(“in”); 
Configuration conf = /*HBaseManager.getHBConnection();*/ new Configuration(); 
Job job = new Job(conf, “my_custom_job”); 
job.setJarByClass(InnerMapper.class); 
FileInputFormat.setInputPaths(job, inputDir); 
job.setMapperClass(InnerMapper.class); 
job.setInputFormatClass(TextInputFormat.class); 
// this is the key to writing to multiple tables in hbase 
job.setOutputFormatClass(MultiTableOutputFormat.class); 
//job.setNumReduceTasks(0); 
//TableMapReduceUtil.addDependencyJars(job); 
//TableMapReduceUtil.addDependencyJars(job.getConfiguration()); 
System.out.println(job.waitForCompletion(true)); 
} 
public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException { 
// TODO Auto-generated method stub 
MultiTableMapper.createSubmittableJob(); 
System.out.println(); 
} 
}