HBase 启用表
HBase 启用表
下面是启用Hbase 表的语法:
enable ‘emp’
下面是例子,演示如何启用表。
hbase(main):005:0> enable 'emp' 0 row(s) in 0.4580 seconds
验证
启用表之后,执行一下scan。如果能看到的模式,那么证明表已成功启用。
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
此命令用于检查表是否被启用。语法如下:
hbase> is_enabled 'table name'
下面的代码验证表emp是否启用。如果启用,它将返回true,如果没有,它会返回false。
hbase(main):031:0> is_enabled 'emp' true 0 row(s) in 0.0440 seconds
使用Java API启用表
要验证一个表是否被启用,使用isTableEnabled()方法;并且使用enableTable()方法使一个表启用。这些方法属于HBaseAdmin类。按照下面给出启用表的步骤。
第1步
HBaseAdmin类的实例如下所示。
// Creating configuration object Configuration conf = HBaseConfiguration.create(); // Creating HBaseAdmin object HBaseAdmin admin = new HBaseAdmin(conf);
第2步
使用isTableEnabled()方法验证表是否被启用,如下所示。
Boolean bool=admin.isTableEnabled("emp");
第3步
如果表未禁用,那么禁用它,如下图所示
if(!bool){ admin.enableTable("emp"); System.out.println("Table enabled"); }
下面给出的是完整的程序,以验证表是否已启用,如果它不是,那么启用它。
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 weather the table is disabled Boolean bool = admin.isTableEnabled("emp"); System.out.println(bool); // Disabling the table using HBaseAdmin object if(!bool){ admin.enableTable("emp"); System.out.println("Table Enabled"); } } }
编译和执行上述程序,结果如下所示。
$javac EnableTable.java $java EnableTable
下面是输出:
false Table Enabled