ALTER NODE GROUP

Description

Modifies information about a node group.

Precautions

• Only a system administrator or a user who has the ALTER permission of a node group can modify the information about the node group.
• 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

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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 [, ... ] )
    | RESIZE TO dest_group_name
};

Parameters

• groupname

  Specifies the name of the node group to be modified.

  Value range: a string. It must comply with the naming convention.

• 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

  Renames 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 values in the group_members and group_buckets columns from the node group specified by src_group_name to the node group specified by groupname.

• 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.

• RESIZE TO dest_group_name

  Specifies a resize flag for the cluster. Set groupname to the source node group before data redistribution and cancel the is_installation flag. Set desst_group_name to the destination node group and set the is_installation flag.

Examples

For details, see Examples in section "CREATE NODE GROUP."

Helpful Links

CREATE NODE GROUP and DROP NODE GROUP