HBase 启用表
使用 HBase Shell 启用表
启用表的语法:
示例
下面给出了启用表格的示例。
hbase(main):005:0> enable 'emp'
0 row(s) in 0.4580 seconds
验证
启用表后,扫描它。如果您可以看到架构,则您的表已成功启用。
hbase(main):006:0> scan 'emp'
ROW COLUMN + CELL
1 column = personal data:city, timestamp = 1417516501, value = hyderabad
1 column = personal data:name, timestamp = 1417525058, value = ramu
1 column = professional data:designation, timestamp = 1417532601, value = manager
1 column = professional data:salary, timestamp = 1417524244109, value = 50000
2 column = personal data:city, timestamp = 1417524574905, value = chennai
2 column = personal data:name, timestamp = 1417524556125, value = ravi
2 column = professional data:designation, timestamp = 14175292204, value = sr:engg
2 column = professional data:salary, timestamp = 1417524604221, value = 30000
3 column = personal data:city, timestamp = 1417524681780, value = delhi
3 column = personal data:name, timestamp = 1417524672067, value = rajesh
3 column = professional data:designation, timestamp = 14175246987, value = jr:engg
3 column = professional data:salary, timestamp = 1417524702514, value = 25000
3 row(s) in 0.0400 seconds
is_enabled
此命令用于查找表是否启用。其语法如下:
hbase> is_enabled 'table name'
以下代码验证名为
emp 的表是否已启用。如果启用,则返回 true,否则返回 false。
hbase(main):031:0> is_enabled 'emp'
true
0 row(s) in 0.0440 seconds
使用 Java API 启用表
验证表是否启用,使用
isTableEnabled()方法;并启用一个表,
enableTable() 方法被使用。这些方法属于
HBaseAdmin 类。请按照以下步骤启用表格。
步骤 1
实例化
HBaseAdmin 类,如下所示。
// Creating configuration object
Configuration conf = HBaseConfiguration.create();
// Creating HBaseAdmin object
HBaseAdmin admin = new HBaseAdmin(conf);
步骤 2
使用
isTableEnabled()方法验证表是否启用,如下所示。
Boolean bool = admin.isTableEnabled("emp");
步骤 3
如果表格没有被禁用,如下所示禁用它。
if(!bool){
admin.enableTable("emp");
System.out.println("Table enabled");
}
下面给出了验证表是否启用的完整程序,如果没有,那么如何启用它。
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.MasterNotRunningException;
import org.apache.hadoop.hbase.client.HBaseAdmin;
public class EnableTable{
public static void main(String args[]) throws MasterNotRunningException, IOException{
// Instantiating configuration class
Configuration conf = HBaseConfiguration.create();
// Instantiating HBaseAdmin class
HBaseAdmin admin = new HBaseAdmin(conf);
// Verifying whether the table is disabled
boolean bool = admin.isTableEnabled("emp");
System.out.println(bool);
// Enabling the table using HBaseAdmin object
if(!bool){
admin.enableTable("emp");
System.out.println("Table Enabled");
}
}
}
编译并执行上述程序,如下所示。
$javac EnableTable.java
$java EnableTable
以下应该是输出: