ALTER SUPER REGION

On this page

The ALTER DATABASE .. ALTER SUPER REGION statement alters an existing super region of a multi-region database.

Synopsis

Parameters

Required privileges

To alter a database's super region, the user must have one of the following:

• Membership to the admin role for the cluster.
• Either ownership or the CREATE privilege for the database.

Considerations

To use super regions, you must keep the following considerations in mind:

• Your cluster must be a multi-region cluster.
• Super regions must be enabled.
• Super regions can only contain one or more database regions that have already been added with ADD REGION.
• Each database region can only belong to one super region. In other words, given two super regions A and B, the set of database regions in A must be disjoint from the set of database regions in B.
• You cannot drop a region that is part of a super region until you either alter the super region to remove it, or drop the super region altogether.

Examples

The examples in this section use the following setup.

Setup

Only a cluster region specified at node startup can be used as a database region.

To follow along with the examples below, start a demo cluster with the --global flag to simulate a multi-region cluster:

$ cockroach demo --global --nodes 9

To see the regions available to the databases in the cluster, use a SHOW REGIONS FROM CLUSTER statement:

SHOW REGIONS FROM CLUSTER;

     region    |  zones
---------------+----------
  europe-west1 | {b,c,d}
  us-east1     | {b,c,d}
  us-west1     | {a,b,c}
(3 rows)

Set up movr database regions

Execute the following statements. They will tell CockroachDB about the database's regions. This information is necessary so that CockroachDB can later move data around to optimize access to particular data from particular regions. For more information about how this works at a high level, see Database Regions.

ALTER DATABASE movr PRIMARY REGION "us-east1";
ALTER DATABASE movr ADD REGION "europe-west1";
ALTER DATABASE movr ADD REGION "us-west1";

Set up movr global tables

Because the data in promo_codes is not updated frequently (a.k.a., "read-mostly"), and needs to be available from any region, the right table locality is GLOBAL.

ALTER TABLE promo_codes SET locality GLOBAL;

Next, alter the user_promo_codes table to have a foreign key into the global promo_codes table. This will enable fast reads of the promo_codes.code column from any region in the cluster.

ALTER TABLE user_promo_codes
  ADD CONSTRAINT user_promo_codes_code_fk
    FOREIGN KEY (code)
    REFERENCES promo_codes (code)
    ON UPDATE CASCADE;

Set up movr regional tables

All of the tables except promo_codes contain rows which are partitioned by region, and updated very frequently. For these tables, the right table locality for optimizing access to their data is REGIONAL BY ROW.

Apply this table locality to the remaining tables. These statements use a CASE statement to put data for a given city in the right region and can take around 1 minute to complete for each table.

• rides

  ALTER TABLE rides ADD COLUMN region crdb_internal_region AS (
    CASE WHEN city = 'amsterdam' THEN 'europe-west1'
         WHEN city = 'paris' THEN 'europe-west1'
         WHEN city = 'rome' THEN 'europe-west1'
         WHEN city = 'new york' THEN 'us-east1'
         WHEN city = 'boston' THEN 'us-east1'
         WHEN city = 'washington dc' THEN 'us-east1'
         WHEN city = 'san francisco' THEN 'us-west1'
         WHEN city = 'seattle' THEN 'us-west1'
         WHEN city = 'los angeles' THEN 'us-west1'
    END
  ) STORED;
  ALTER TABLE rides ALTER COLUMN REGION SET NOT NULL;
  ALTER TABLE rides SET LOCALITY REGIONAL BY ROW AS "region";
  

• user_promo_codes

  ALTER TABLE user_promo_codes ADD COLUMN region crdb_internal_region AS (
    CASE WHEN city = 'amsterdam' THEN 'europe-west1'
         WHEN city = 'paris' THEN 'europe-west1'
         WHEN city = 'rome' THEN 'europe-west1'
         WHEN city = 'new york' THEN 'us-east1'
         WHEN city = 'boston' THEN 'us-east1'
         WHEN city = 'washington dc' THEN 'us-east1'
         WHEN city = 'san francisco' THEN 'us-west1'
         WHEN city = 'seattle' THEN 'us-west1'
         WHEN city = 'los angeles' THEN 'us-west1'
    END
  ) STORED;
  ALTER TABLE user_promo_codes ALTER COLUMN REGION SET NOT NULL;
  ALTER TABLE user_promo_codes SET LOCALITY REGIONAL BY ROW AS "region";
  

• users

  ALTER TABLE users ADD COLUMN region crdb_internal_region AS (
    CASE WHEN city = 'amsterdam' THEN 'europe-west1'
         WHEN city = 'paris' THEN 'europe-west1'
         WHEN city = 'rome' THEN 'europe-west1'
         WHEN city = 'new york' THEN 'us-east1'
         WHEN city = 'boston' THEN 'us-east1'
         WHEN city = 'washington dc' THEN 'us-east1'
         WHEN city = 'san francisco' THEN 'us-west1'
         WHEN city = 'seattle' THEN 'us-west1'
         WHEN city = 'los angeles' THEN 'us-west1'
    END
  ) STORED;
  ALTER TABLE users ALTER COLUMN REGION SET NOT NULL;
  ALTER TABLE users SET LOCALITY REGIONAL BY ROW AS "region";
  

• vehicle_location_histories

  ALTER TABLE vehicle_location_histories ADD COLUMN region crdb_internal_region AS (
    CASE WHEN city = 'amsterdam' THEN 'europe-west1'
         WHEN city = 'paris' THEN 'europe-west1'
         WHEN city = 'rome' THEN 'europe-west1'
         WHEN city = 'new york' THEN 'us-east1'
         WHEN city = 'boston' THEN 'us-east1'
         WHEN city = 'washington dc' THEN 'us-east1'
         WHEN city = 'san francisco' THEN 'us-west1'
         WHEN city = 'seattle' THEN 'us-west1'
         WHEN city = 'los angeles' THEN 'us-west1'
    END
  ) STORED;
  ALTER TABLE vehicle_location_histories ALTER COLUMN REGION SET NOT NULL;
  ALTER TABLE vehicle_location_histories SET LOCALITY REGIONAL BY ROW AS "region";
  

• vehicles

  ALTER TABLE vehicles ADD COLUMN region crdb_internal_region AS (
    CASE WHEN city = 'amsterdam' THEN 'europe-west1'
         WHEN city = 'paris' THEN 'europe-west1'
         WHEN city = 'rome' THEN 'europe-west1'
         WHEN city = 'new york' THEN 'us-east1'
         WHEN city = 'boston' THEN 'us-east1'
         WHEN city = 'washington dc' THEN 'us-east1'
         WHEN city = 'san francisco' THEN 'us-west1'
         WHEN city = 'seattle' THEN 'us-west1'
         WHEN city = 'los angeles' THEN 'us-west1'
    END
  ) STORED;
  ALTER TABLE vehicles ALTER COLUMN REGION SET NOT NULL;
  ALTER TABLE vehicles SET LOCALITY REGIONAL BY ROW AS "region";
  

Enable super regions

To enable super regions, set the enable_super_regions session setting to 'on':

SET enable_super_regions = 'on';

SET

You can also set the sql.defaults.super_regions.enabled cluster setting to true:

SET CLUSTER SETTING  sql.defaults.super_regions.enabled = true;

SET CLUSTER SETTING

Alter a super region

This example assumes you have already added a "usa" super region as shown in the example Add a super region to a database. If you wanted to drop the region us-west1, you would first need to remove it from the super region.

To remove a region from a super region, use the ALTER DATABASE ... ALTER SUPER REGION statement and list only the regions that should remain in the super region:

ALTER DATABASE movr ALTER SUPER REGION "usa" VALUES "us-east1";

ALTER DATABASE ALTER SUPER REGION

To add a region to a super region, alter the super region as shown above to be a list of regions that includes the existing and the new regions.

Allow user to modify a primary region that is part of a super region

By default, you may not change the primary region of a multi-region database when that region is part of a super region. This is a safety setting designed to prevent you from accidentally moving the data for a regional table that is meant to be stored in the super region out of that super region, which could break your data domiciling setup.

If you are sure about what you are doing, you can allow modifying the primary region by setting the alter_primary_region_super_region_override session setting to 'on':

SET alter_primary_region_super_region_override = 'on';

SET

You can also accomplish this by setting the sql.defaults.alter_primary_region_super_region_override.enable cluster setting to true:

SET CLUSTER SETTING  sql.defaults.alter_primary_region_super_region_override.enable = true;

SET CLUSTER SETTING

See also

• Multi-Region Capabilities Overview
• Super regions
• SET PRIMARY REGION
• SHOW SUPER REGIONS
• DROP SUPER REGION
• ADD SUPER REGION
• DROP REGION
• SHOW REGIONS
• ALTER TABLE
• ALTER DATABASE
• SQL Statements

Was this helpful?