hbase命名空间

在HBase中，namespace命名空间指对一组表的逻辑分组，类似于数据库，便于对表在业务上划分

HBase系统默认定义了两个缺省的namespace

• hbase：系统内建表，包括namespace和meta表
• default：用户建表时未指定namespace的表都创建在此

hbase(main):224:0> list_namespace
NAMESPACE                                                                                                                                                                       
default                                                                                                                                                                         
hbase                                                                                                                                                                           
2 row(s)
Took 0.2533 seconds

hbase(main):223:0> help "namespace"

Command: alter_namespace Alter namespace properties.

To add/modify a property:

hbase> alter_namespace 'ns1', {METHOD => 'set', 'PROPERTY_NAME' => 'PROPERTY_VALUE'}

To delete a property:

hbase> alter_namespace 'ns1', {METHOD => 'unset', NAME=>'PROPERTY_NAME'}

Command: create_namespace Create namespace; pass namespace name, and optionally a dictionary of namespace configuration. Examples:

hbase> create_namespace 'ns1'   hbase> create_namespace 'ns1', {'PROPERTY_NAME'=>'PROPERTY_VALUE'}

Command: describe_namespace Describe the named namespace. For example:   hbase> describe_namespace 'ns1'

Command: drop_namespace Drop the named namespace. The namespace must be empty.

Command: list_namespace List all namespaces in hbase. Optional regular expression parameter could be used to filter the output. Examples:

hbase> list_namespace   hbase> list_namespace 'abc.*'

Command: list_namespace_tables List all tables that are members of the namespace. Examples:

hbase> list_namespace_tables 'ns1'

创建命名空间

hbase(main):226:0> create_namespace 'testdb'
Took 2.1094 seconds

列出所有命名空间                                                                                                                                                         
hbase(main):227:0> list_namespace
NAMESPACE                                                                                                                                                                       
default                                                                                                                                                                         
hbase                                                                                                                                                                           
testdb                                                                                                                                                                          
3 row(s)
Took 0.0217 seconds

在namespace创建表

hbase(main):229:0> create 'testdb:mytable','basicinfo'
Created table testdb:mytable
Took 2.3445 seconds                                                                                                                                                             
=> Hbase::Table - testdb:mytable

查看命名空间下的表

hbase(main):238:0> list_namespace_tables 'testdb'
TABLE                                                                                                                                                                           
mytable                                                                                                                                                                         
1 row(s)
Took 0.0139 seconds                                                                                                                                                             
=> ["mytable"]

删除命名空间

hbase(main):239:0> drop_namespace 'testdb'

ERROR: org.apache.hadoop.hbase.constraint.ConstraintException: Only empty namespaces can be removed. Namespace testdb has 1 tables

提示只有空的命名空间可以删除，删除命名空间前。需要先删除命名空间的表

hbase(main):241:0> disable 'testdb:mytable'
Took 0.7931 seconds                                                                                                                                                             
hbase(main):242:0> drop 'testdb:mytable'
Took 0.9203 seconds                                                                                                                                                             
hbase(main):243:0> drop_namespace 'testdb'
Took 0.5726 seconds