Apache HBase DDL Commands

HBase - Basic Commands

HBase - DML Commands

DDL commands are table management commands which are used to create a table, list table, describe the table, and so on.

Apache HBase supports the below list of DDL commands.

1. Create Table
2. List
3. Describe
4. Disable
5. Disable_all
6. Show_filters
7. Drop Table
8. Drop_all
9. Is_enabled
10. Alter

Let us see each DDL command in detail.

1. Create Table

Using create table command we can create a table by specifying the table name and column family.

Syntax hbase(main):006:0> create ‘table name’,’column family’

Here we have created a table ‘employee’ with a two-column family (‘emp_address’,’emp_records’).

Command hbase(main):006:0> create 'employee','emp_address','emp_records'

Output

2. List

List command is used to display the tables which are present in HBase.

Syntax hbase(main):006:0> list

Command hbase(main):006:0> list

Output

3. Describe

Describe command is used to display the table name with column families, associated filters, versions, and few more details.

Syntax hbase(main):030:0> describe 'tablename'

Command hbase(main):030:0> describe 'employee'

Output

4. Disable

Disable command is used to disable a table. It is used when a table needs to be dropped in that case first we need to disable the table and then we can drop it.

Syntax hbase(main):031:0> disable 'tablename'

Command hbase(main):031:0> disable 'employee'

Output

5. Disable_all

Disable_all command is used to disable all tables. It is used when all table needs to be dropped in that case first we need to disable all tables and then we can drop.

Syntax hbase(main):035:0> disable_all  'matching tablename’

Command hbase(main):035:0> disable_all 'employee'

Output

6. Show_filters

Show_filters command is used to display all filters present in HBase such as DependentColumnFilter, KeyOnlyFilter, ColumnCountGetFilter, and so on.

Syntax hbase(main):036:0> show_filters

Command hbase(main):036:0> show_filters

Output

7. Drop_Table

Before performing the “drop” or “delete” table command first we need to disable it and then we can drop or delete a table.

Syntax hbase(main):038:0> drop ‘table_name’

Command hbase(main):038:0> drop 'employee'

Output

8. Drop_all

Drop_all command will drop all tables which are matching in the given regex but before performing the “drop_all” command first we need to disable it.

Syntax hbase(main):042:0> drop_all 'regex'

Command hbase(main):042:0> drop_all 'employee'

Output

9. Is_enabled

Is_enabled command is used to check if a table enables or not. If the table is disabled then this command will return “false” and if the table is not disabled then this command will return “true”.

Syntax hbase(main):044:0> is_enabled ‘table_name’

Command hbase(main):044:0> is_enabled 'employee'

Output

10. Alter

Alter command is used to make changes to an existing table. By using this command, we can change the maximum number of cells of a column family, set and delete table scope operators, and delete a column family from a table.

Syntax hbase(main):001:0>  alter <tablename>, NAME=><column familyname>, VERSIONS=>5

Using alter command we will add a new column family 'emp_contact' in the employee table.

Let us see with the below example.

Command hbase(main):001:0> alter 'employee', NAME='emp_contact', VERSIONS=>5

Output

Using alter command we will add multiple column families such as 'emp_id' and 'dept_id' in the employee table.

Let us see with the below example.

Command hbase(main):001:0> alter 'employee','emp_address','emp_contact','emp_records', {NAME => 'emp_id', IN_MEMORY => true},{NAME => 'dept_id', VERSIONS => 6}

Output

Using alter command we can delete the column family.

Let us see with below example in which we are deleting the “dept_id” column family from the “employee” table.

Command hbase(main):003:0> alter 'employee', 'delete' => 'dept_id'

Output