ALTER NODE GROUP

Description

Changes the information about a cluster node group.

Precautions

Only the system administrator or a user who has been granted the ALTER permission for the node group can modify the node group information.
Node group modification is an internal operation of the system. Except SET DEFAULT, other operations must be performed in maintenance mode (by calling SET xc_maintenance_mode=on;).
ALTER NODE GROUP can be used only within a database. To avoid data inconsistency in DBMS, do not manually run this SQL statement.

Syntax

    
         ALTER NODE GROUP groupname
{ SET DEFAULT
    | RENAME TO new_group_name
    | SET TABLE GROUP new_group_name
    | COPY BUCKETS FROM src_group_name
    | ADD NODE ( nodename [, ... ] )
    | DELETE NODE ( nodename [, ... ] )
    | SET SEQUENCE ( TO LOCAL | TO ALL NODE )
};

Parameters

groupname
Specifies the name of the node group to be modified.

Value range: a string complying with Identifier Description.
SET DEFAULT
Sets in_redistribution to 'y' for all node groups excluding the one specified by groupname. To be compatible with earlier versions, this syntax is retained and does not need to be executed in maintenance mode.
RENAME TO new_group_name
Changes the name of the node group specified by groupname to new_group_name.
SET TABLE GROUP new_group_name
Changes all the group_names in the pgroup columns of the pgxc_class tables on all CNs to new_group_name.
COPY BUCKETS FROM src_group_name
Copies the contents of the group_members and group_buckets columns from the node group specified by src_group_name to the node group specified by groupname.

The current version does not support the COPY BUCKETS FROM option.
ADD NODE ( nodename [, ... ] )
Adds nodes from the node group specified by groupname. After the statement execution, the new nodes are registered with the PGXC_NODE system catalog. This statement only modifies the system catalog and does not add nodes or redistribute data. Do not call this statement. You can observe the impact of the statement in the PGXC_GROUP system catalog.
DELETE NODE ( nodename [, ... ] )
Deletes nodes from the node group specified by groupname. The deleted nodes still exist in the PGXC_NODE system catalog. This statement only modifies the system catalog and does not delete nodes or redistribute data. Do not call this statement. You can observe the impact of the statement in the PGXC_GROUP system catalog.
SET SEQUENCE ( TO LOCAL | TO ALL NODE )
Configures the sequence of the cluster to the local node or all nodes.

Examples

-- Query the initial cluster DN status.
gaussdb=# SELECT node_name, nodeis_preferred FROM pgxc_node WHERE node_type = 'D' ORDER BY 1;
 node_name | nodeis_preferred
-----------+------------------
 dn_6001_6002_6003 | f
 dn_6004_6005_6006 | f
 dn_6007_6008_6009 | f
(3 rows)

-- Create a node group and replace dn_6001_6002_6003 with the actual node name obtained in the previous step.
gaussdb=# CREATE NODE GROUP test_group WITH ( dn_6001_6002_6003 );

-- Changes the name of the created node group to test_group_new. This must be implemented in the maintenance mode (by calling SET xc_maintenance_mode=on;).
gaussdb=# set xc_maintenance_mode=on;
gaussdb=# ALTER NODE GROUP test_group RENAME TO test_group_new;

-- Query the node group.
gaussdb=# SELECT group_name, group_members FROM pgxc_group;
   group_name   |   group_members   
----------------+-------------------
 group_version1 | 16384 16388 16394
 test_group_new | 16384
(2 rows)

-- Delete the node group and disable the maintenance mode.
gaussdb=# DROP NODE GROUP test_group_new;
gaussdb=# SET xc_maintenance_mode=off;