ALTER NODE GROUP

Function

ALTER NODE GROUP modifies the information about a node group.

Precautions

• Only the 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 invoking 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 VCGROUP RENAME TO new_group_name
    | SET NOT VCGROUP
    | SET TABLE GROUP new_group_name
    | COPY BUCKETS FROM src_group_name
    | ADD NODE ( nodename [, ... ] )
    | DELETE NODE ( nodename [, ... ] )
    | RESIZE TO dest_group_name
    | SET VCGROUP WITH GROUP new_group_name

Parameter Description

• 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 VCGROUP RENAME TO new_group_name

  Converts a physical cluster into a logical cluster. (The current feature is a lab feature. Contact Huawei engineers for technical support before using it.) After the conversion, groupname is the logical cluster name, and the original physical cluster name is changed to new_group_name.

• SET NOT VCGROUP

  Converts all logical clusters to common node groups and changes group_kind from 'v' to 'n' for all of them. (The current feature is a lab feature. Contact Huawei engineers for technical support before using it.)

• 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 invoke this statement.

• 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 invoke this statement.

• RESIZE TO dest_group_name

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

• SET VCGROUP WITH GROUP new_group_name

  Converts a physical cluster into a logical cluster. After the conversion, groupname is still the physical cluster, and new_group_name is the name of the logical cluster. (The current feature is a lab feature. Contact Huawei engineers for technical support before using it.)