Cluster functions

• 1: CANCEL_REBALANCE_CLUSTER
• 2: DISABLE_LOCAL_SEGMENTS
• 3: ENABLE_ELASTIC_CLUSTER
• 4: ENABLE_LOCAL_SEGMENTS
• 5: REALIGN_CONTROL_NODES
• 6: REBALANCE_CLUSTER
• 7: RELOAD_SPREAD
• 8: SET_CONTROL_SET_SIZE
• 9: SET_SCALING_FACTOR
• 10: START_REBALANCE_CLUSTER

1 - CANCEL_REBALANCE_CLUSTER

Stops any rebalance task that is currently in progress or is waiting to execute.

This is a meta-function. You must call meta-functions in a top-level SELECT statement.

Behavior type

Syntax

CANCEL_REBALANCE_CLUSTER()

Privileges

Superuser

Examples

=> SELECT CANCEL_REBALANCE_CLUSTER();
 CANCEL_REBALANCE_CLUSTER
--------------------------
 CANCELED
(1 row)

See also

• START_REBALANCE_CLUSTER
• REBALANCE_CLUSTER

2 - DISABLE_LOCAL_SEGMENTS

Disables local data segmentation, which breaks projections segments on nodes into containers that can be easily moved to other nodes. See Local data segmentation for details.

This is a meta-function. You must call meta-functions in a top-level SELECT statement.

Behavior type

Syntax

DISABLE_LOCAL_SEGMENTS()

Privileges

Superuser

Examples

=> SELECT DISABLE_LOCAL_SEGMENTS();
 DISABLE_LOCAL_SEGMENTS
------------------------
 DISABLED
(1 row)

3 - ENABLE_ELASTIC_CLUSTER

Enables elastic cluster scaling, which makes enlarging or reducing the size of your database cluster more efficient by segmenting a node's data into chunks that can be easily moved to other hosts.

This is a meta-function. You must call meta-functions in a top-level SELECT statement.

Behavior type

Syntax

ENABLE_ELASTIC_CLUSTER()

Privileges

Superuser

Examples

=> SELECT ENABLE_ELASTIC_CLUSTER();
 ENABLE_ELASTIC_CLUSTER
------------------------
 ENABLED
(1 row)

4 - ENABLE_LOCAL_SEGMENTS

Enables local storage segmentation, which breaks projections segments on nodes into containers that can be easily moved to other nodes. See Local data segmentation for more information.

This is a meta-function. You must call meta-functions in a top-level SELECT statement.

Behavior type

Syntax

ENABLE_LOCAL_SEGMENTS()

Privileges

Superuser

Examples

=> SELECT ENABLE_LOCAL_SEGMENTS();
 ENABLE_LOCAL_SEGMENTS
-----------------------
 ENABLED
(1 row)

5 - REALIGN_CONTROL_NODES

Causes Vertica to re-evaluate which nodes in the cluster or subcluster are control nodes and which nodes are assigned to them as dependents when large cluster is enabled. Call this function after altering fault groups in an Enterprise Mode database, or changing the number of control nodes in either database mode. After calling this function, query the V_CATALOG.CLUSTER_LAYOUT system table to see the proposed new layout for nodes in the cluster. You must also take additional steps before the new control node assignments take effect. See Changing the number of control nodes and realigning for details.

This is a meta-function. You must call meta-functions in a top-level SELECT statement.

Behavior type

Syntax

In Enterprise Mode:

REALIGN_CONTROL_NODES()

In Eon Mode:

REALIGN_CONTROL_NODES('subcluster_name')

Parameters

subcluster_name

The name of the subcluster where you want to realign control nodes. Only the nodes in this subcluster are affected. Other subclusters are unaffected. Only allowed when the database is running in Eon Mode.

Privileges

Examples

In an Enterprise Mode database, choose control nodes from all nodes and assign the remaining nodes to a control node:

=> SELECT REALIGN_CONTROL_NODES();

In an Eon Mode database, re-evaluate the control node assignments in the subcluster named analytics:

=> SELECT REALIGN_CONTROL_NODES('analytics');

See also

• Changing the number of control nodes and realigning
• Fault groups

6 - REBALANCE_CLUSTER

Rebalances the database cluster synchronously as a session foreground task. REBALANCE_CLUSTER returns only after the rebalance operation is complete. If the current session ends, the operation immediately aborts. To rebalance the cluster as a background task, call START_REBALANCE_CLUSTER.

On large cluster arrangements, you typically call REBALANCE_CLUSTER in a flow (see Changing the number of control nodes and realigning). After you change the number and distribution of control nodes (spread hosts), run REBALANCE_CLUSTER to achieve fault tolerance.

For detailed information about rebalancing tasks, see Rebalancing data across nodes.

This is a meta-function. You must call meta-functions in a top-level SELECT statement.

Behavior type

Syntax

REBALANCE_CLUSTER()

Privileges

Superuser

Examples

=> SELECT REBALANCE_CLUSTER();
REBALANCE_CLUSTER
-------------------
 REBALANCED
(1 row)

7 - RELOAD_SPREAD

Updates cluster changes to the catalog's Spread configuration file. These changes include:

• New or realigned control nodes

• New Spread hosts or fault group

• New or dropped cluster nodes

This function is often used in a multi-step process for large and elastic cluster arrangements. Calling it might require you to restart the database. You must then rebalance the cluster to realize fault tolerance. For details, see Defining and Realigning Control Nodes.

This is a meta-function. You must call meta-functions in a top-level SELECT statement.

Behavior type

Syntax

RELOAD_SPREAD( true )

Parameters

true

Updates cluster changes related to control message responsibilities to the Spread configuration file.

Privileges

Examples

Update the cluster with changes to control messaging:

=> SELECT reload_spread(true);
 reload_spread
---------------
 reloaded
(1 row)

See also

8 - SET_CONTROL_SET_SIZE

Sets the number of control nodes that participate in the spread service when large cluster is enabled. If the database is running in Enterprise Mode, this function sets the number of control nodes for the entire database cluster. If the database is running in Eon Mode, this function sets the number of control nodes in the subcluster you specify. See Large cluster for more information.

This is a meta-function. You must call meta-functions in a top-level SELECT statement.

Behavior type

Syntax

In Enterprise Mode:

SET_CONTROL_SET_SIZE( control_nodes )

In Eon Mode:

SET_CONTROL_SET_SIZE('subcluster_name', control_nodes )

Parameters

subcluster_name

The name of the subcluster where you want to set the number of control nodes. Only allowed when the database is running in Eon Mode.

control_nodes

The number of control nodes to assign to the cluster (when in Enterprise Mode) or subcluster (when in Eon Mode). Value can be one of the following:

• Positive integer value: Vertica assigns the number of control nodes you specify to the cluster or subcluster. This value can be larger than the current node count. This value cannot be larger than 120 (the maximum number of control nodes for a database). In Eon Mode, the total of this value plus the number of control nodes set for all other subclusters cannot be more than 120.

• -1: Makes every node in the cluster or subcluster into control nodes. This value effectively disables large cluster for the cluster or subcluster.

Privileges

Examples

In an Enterprise Mode database, set the number of control nodes for the entire cluster to 5:

=> SELECT set_control_set_size(5);
 SET_CONTROL_SET_SIZE
----------------------
 Control size set
(1 row)

See also

• Changing the number of control nodes and realigning

9 - SET_SCALING_FACTOR

Sets the scaling factor that determines the number of storage containers used when rebalancing the database and when using local data segmentation is enabled. See Cluster Scaling for details.

This is a meta-function. You must call meta-functions in a top-level SELECT statement.

Behavior type

Syntax

SET_SCALING_FACTOR( factor )

Parameters

factor

An integer value between 1 and 32. Vertica uses this value to calculate the number of storage containers each projection is broken into when rebalancing or when local data segmentation is enabled.

Privileges

Superuser

Best practices

The scaling factor determines the number of storage containers that Vertica uses to store each projection across the database during rebalancing when local segmentation is enabled. When setting the scaling factor, follow these guidelines:

• The number of storage containers should be greater than or equal to the number of partitions multiplied by the number of local segments:

  num-storage-containers>= (num-partitions*num-local-segments )

• Set the scaling factor high enough so rebalance can transfer local segments to satisfy the skew threshold, but small enough so the number of storage containers does not result in too many ROS containers, and cause ROS pushback. The maximum number of ROS containers (by default 1024) is set by configuration parameter ContainersPerProjectionLimit.

Examples

=> SELECT SET_SCALING_FACTOR(12);
 SET_SCALING_FACTOR
--------------------
 SET
(1 row)

10 - START_REBALANCE_CLUSTER

Asynchronously rebalances the database cluster as a background task. This function returns immediately after the rebalancing operation is complete. Rebalancing persists until the operation is complete, even if you close the current session or the database shuts down. In the case of shutdown, rebalancing resumes after the cluster restarts. To stop the rebalance operation, call CANCEL_REBALANCE_CLUSTER.

For detailed information about rebalancing tasks, see Rebalancing data across nodes.

This is a meta-function. You must call meta-functions in a top-level SELECT statement.

Behavior type

Syntax

START_REBALANCE_CLUSTER()

Privileges

Superuser

Examples

=> SELECT START_REBALANCE_CLUSTER();
 START_REBALANCE_CLUSTER
-------------------------
 REBALANCING
(1 row)

See also