这里我们用一个学生成绩表作为例子,对HBase的基本操作和基本概念进行讲解:
下面是学生的成绩表:
| name | grade | course:math | course:art |
|---|---|---|---|
| Tom | 1 | 87 | 97 |
| Jerry | 2 | 100 | 80 |
这里grade对于表来说是一个列,course对于表来说是一个列族,这个列族由两个列组成:math和art,
当然我们可以根据我们的需要在course中建立更多的列族,如computer,physics等相应的列添加入course列族.
有了上面的想法和需求,我们就可以在HBase中建立相应的数据表啦!
建立一个表格 scores 具有两个列族grade 和courese
hbase(main):002:0> create 'scores', 'grade', 'course' 0 row(s) in 4.1610 seconds查看当先HBase中具有哪些表
hbase(main):003:0> list scores 1 row(s) in 0.0210 seconds查看表的构造
hbase(main):004:0> describe 'scores' {NAME => 'scores', IS_ROOT => 'false', IS_META => 'false', FAMILIES => [{NAME => 'course', BLOOMFILTER => 'false', IN_MEMORY => 'false', LENGTH => '2147483647', BLOCKCACHE => 'false', VERSIONS => '3', TTL => '-1', COMPRESSION => 'NONE'}, {NAME => 'grade', BLOOMFILTER => 'false', IN_MEMORY => 'false', LENGTH => '2147483647', BLOCKCACHE => 'false', VERSIONS => '3', TTL => '-1', COMPRESSION => 'NONE'}]} 1 row(s) in 0.0130 seconds加入一行数据,行名称为 Tom 列族grad的列名为”” 值位1
hbase(main):005:0> put 'scores', 'Tom', 'grade:', '1' 0 row(s) in 0.0070 seconds给Tom这一行的数据的列族添加一列
hbase(main):006:0> put 'scores', 'Tom', 'course:math', '87' 0 row(s) in 0.0040 seconds给Tom这一行的数据的列族添加一列
hbase(main):007:0> put 'scores', 'Tom', 'course:art', '97' 0 row(s) in 0.0030 seconds加入一行数据,行名称为 Jerry 列族grad的列名为”” 值位2
hbase(main):008:0> put 'scores', 'Jerry', 'grade:', '2' 0 row(s) in 0.0040 seconds给Jerry这一行的数据的列族添加一列
hbase(main):009:0> put 'scores', 'Jerry', 'course:math', '100' 0 row(s) in 0.0030 seconds给Jerry这一行的数据的列族添加一列
hbase(main):010:0> put 'scores', 'Jerry', 'course:art', '80' 0 row(s) in 0.0050 seconds查看scores表中Tom的相关数据
hbase(main):011:0> get 'scores', 'Tom' COLUMN CELL course:art timestamp=1224726394286, value=97 course:math timestamp=1224726377027, value=87 grade: timestamp=1224726360727, value=1 3 row(s) in 0.0070 seconds查看scores表中所有数据
hbase(main):012:0> scan 'scores' ROW COLUMN+CELL Tom column=course:art, timestamp=1224726394286, value=97 Tom column=course:math, timestamp=1224726377027, value=87 Tom column=grade:, timestamp=1224726360727, value=1 Jerry column=course:art, timestamp=1224726424967, value=80 Jerry column=course:math, timestamp=1224726416145, value=100 Jerry column=grade:, timestamp=1224726404965, value=2 6 row(s) in 0.0410 seconds查看scores表中所有数据courses列族的所有数据
hbase(main):013:0> scan 'scores',{COLUMN=>['course']} ROW COLUMN+CELL Jerry column=course:art, timestamp=1441953970540, value=80 Jerry column=course:math, timestamp=1441953959676, value=100 Tom column=course:art, timestamp=1441953935469, value=97 Tom column=course:math, timestamp=1441953923125, value=87 2 row(s) in 0.0640 seconds
上面就是HBase的基本shell操作的一个例子,可以看出,hbase的shell还是比较简单易用的,
从中也可以看出HBase shell缺少很多传统sql中的一些类似于like等相关操作,
当然,HBase作为BigTable的一个开源实现,而BigTable是作为 google业务的支持模型,
很多sql语句中的一些东西可能还真的不需要.
当然,通过程序我们也可以对HBase进行相关的操作.下面的程序就完成了上面shell操作的内容:
import java.io.IOException;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.util.Map;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.HTableDescriptor;
import org.apache.hadoop.hbase.HColumnDescriptor;
import org.apache.hadoop.hbase.client.HBaseAdmin;
import org.apache.hadoop.hbase.client.HTable;
import org.apache.hadoop.hbase.io.BatchUpdate;
import org.apache.hadoop.hbase.io.RowResult;
import org.apache.hadoop.hbase.io.Cell;
import org.apache.hadoop.hbase.util.Writables;
public class HBaseBasic {
public static void main(String[] args) throws Exception {
HBaseConfiguration config = new HBaseConfiguration();
HBaseAdmin admin = new HBaseAdmin(config);
if (admin.tableExists("scores")) {
System.out.println("drop table");
admin.disableTable("scores");
admin.deleteTable("scores");
}
System.out.println("create table");
HTableDescriptor tableDescripter = new HTableDescriptor("scores".getBytes());
tableDescripter.addFamily(new HColumnDescriptor("grade:"));
tableDescripter.addFamily(new HColumnDescriptor("course:"));
admin.createTable(tableDescripter);
HTable table = new HTable(config, "scores");
System.out.println("add Tom's data");
BatchUpdate tomUpdate = new BatchUpdate("Tom");
tomUpdate.put("grade:", Writables.getBytes(new IntWritable(1)));
tomUpdate.put("course:math", Writables.getBytes(new IntWritable(87)));
tomUpdate.put("course:art", Writables.getBytes(new IntWritable(97)));
table.commit(tomUpdate);
System.out.println("add Jerry's data");
BatchUpdate jerryUpdate = new BatchUpdate("Jerry");
jerryUpdate.put("grade:", Writables.getBytes(new IntWritable(2)));
jerryUpdate.put("course:math", Writables.getBytes(new IntWritable(100)));
jerryUpdate.put("course:art", Writables.getBytes(new IntWritable(80)));
table.commit(jerryUpdate);
for (RowResult row : table.getScanner(new String[] { "course:" })) {
System.out.format("ROW\t%s\n", new String(row.getRow()));
for (Map.Entry<byte[], Cell> entry : row.entrySet()) {
String column = new String(entry.getKey());
Cell cell = entry.getValue();
IntWritable value = new IntWritable();
Writables.copyWritable(cell.getValue(), value);
System.out.format(" COLUMN\t%s\t%d\n", column, value.get());
}
}
}
}
输出如下:
drop table
09/07/11 08:51:59 INFO client.HBaseAdmin: Disabled scores
09/07/11 08:51:59 INFO client.HBaseAdmin: Deleted scores
create table
add Tom's data
add Jerry's data
ROW Tom
COLUMN course:art 97
COLUMN course:math 87
ROW Jerry
COLUMN course:art 80
COLUMN course:math 100