ALTER DATABASE

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The ALTER DATABASE statement applies a schema change to a database.

Required privileges

Refer to the respective subcommands.

Synopsis

Parameters

Additional parameters are documented for the respective subcommands.

Subcommands

ADD REGION

ALTER DATABASE .. ADD REGION adds a region to a multi-region database. While CockroachDB processes an index modification or changing a table to or from a REGIONAL BY ROW table, attempting to drop a region from the database containing that REGIONAL BY ROW table will produce an error. Similarly, while this statement is running, all index modifications and locality changes on REGIONAL BY ROW tables will be blocked.

For examples, see Manage regions.

Required privileges

To add a region to a database, 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 and all REGIONAL BY ROW tables in the database.

Parameters

For usage, see Synopsis.

ADD SUPER REGION

ALTER DATABASE .. ADD SUPER REGION adds a super region to a multi-region database.

To use super regions, 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 ALTER DATABASE ... 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.

For examples, see Manage super regions.

Required privileges

To add a super region to a database, 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.

Parameters

For usage, see Synopsis.

ALTER LOCALITY

ALTER DATABASE .. ALTER LOCALITY provides a customization tool for advanced users to persistently modify the configuration generated by the standard multi-region SQL abstractions on a per-region basis.

The feature this statement enables is also known as Zone Config Extensions. For more information about how it works, and the benefits over using the low-level CONFIGURE ZONE statement, see Zone Config Extensions.

For examples, see Use Zone Config Extensions.

Required privileges

The user must be a member of the admin or owner roles, or have the CREATE privilege on the database.

Parameters

For usage, see Synopsis.

ALTER SUPER REGION

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

To use super regions, 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 ALTER DATABASE ... 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.

For examples, see Manage super regions.

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.

Parameters

For usage, see Synopsis.

CONFIGURE ZONE

ALTER DATABASE ... CONFIGURE ZONE is used to add, modify, reset, or remove replication zones for a database. To view details about existing replication zones, use SHOW ZONE CONFIGURATIONS. For more information about replication zones, see Replication Controls.

You can use replication zones to control the number and location of replicas for specific sets of data, both when replicas are first added and when they are rebalanced to maintain cluster equilibrium.

For examples, see Replication Controls.

Required privileges

The user must be a member of the admin role or have been granted CREATE or ZONECONFIG privileges. To configure system objects, the user must be a member of the admin role.

Parameters

For usage, see Synopsis.

DROP REGION

ALTER DATABASE .. DROP REGION drops a region from a multi-region database. While CockroachDB processes an index modification or changing a table to or from a REGIONAL BY ROW table, attempting to drop a region from the database containing that REGIONAL BY ROW table will produce an error. Similarly, while this statement is running, all index modifications and locality changes on REGIONAL BY ROW tables will be blocked.

You cannot drop a region from a multi-region database if:

• The region is set as the primary region, unless it is the last remaining region.
• The region is set as the secondary region. To drop the region, you must first unset the secondary region using DROP SECONDARY REGION.
• The database uses the REGION survival goal and there are only three regions configured on the database.

For examples, see Manage regions.

Required privileges

To drop a region from a database, the user must have one of the following:

• Membership to the admin role for the cluster.
• Membership to the owner role, or the CREATE privilege, for the database and all REGIONAL BY ROW tables in the database.

Parameters

For usage, see Synopsis.

DROP SECONDARY REGION

ALTER DATABASE .. DROP SECONDARY REGION unsets the secondary region (if set) from a multi-region database.

The secondary region is used for failover purposes: if the primary region fails, the secondary region acts as the new primary region. For more information, see Secondary regions.

For examples, see Manage regions.

Required privileges

To unset a secondary region on a database, the user must have one of the following:

• Membership to the admin role for the cluster.
• Membership to the owner role, or the CREATE privilege for the database.

DROP SUPER REGION

ALTER DATABASE .. DROP SUPER REGION drops a super region from a multi-region database.

To use super regions, 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 ALTER DATABASE ... 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.

For examples, see Manage super regions.

Required privileges

To drop a super region from a database, 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.

Parameters

For usage, see Synopsis.

OWNER TO

ALTER DATABASE ... OWNER TO is used to change the owner of a database.

For examples, see Change database owner.

Required privileges

To change the owner of a database, the user must be an admin user, or the current owner of the database and a member of the new owner role. The user must also have the CREATEDB privilege.

Parameters

For usage, see Synopsis.

PLACEMENT

ALTER DATABASE ... PLACEMENT is used to set the replica placement policy (DEFAULT or RESTRICTED) for a multi-region database's regional tables. Regional tables are those with REGIONAL BY ROW or REGIONAL BY TABLE localities.

ALTER DATABASE ... PLACEMENT RESTRICTED constrains the voting and non-voting replica placement for the database's tables to the home regions associated with those tables. This is a way of opting out of non-voting replicas for regional tables to accomplish one or more of the following goals:

• Implement a data domiciling strategy.
• Reduce the amount of data stored on the cluster.
• Reduce the overhead of replicating data across a large number of regions (e.g., 10 or more) for databases with heavier write loads.

Note that ALTER DATABASE ... PLACEMENT RESTRICTED does not allow you to opt out of placing non-voting replicas entirely. For example, GLOBAL tables in the database will remain unaffected by this statement. GLOBAL tables are designed to have replicas placed across all available cluster regions to ensure fast local reads.

For examples, see Set replica placement policy.

Required privileges

To use this statement, the user must have one of the following:

• Membership to the admin role for the cluster.
• Ownership or the CREATE privilege for the database and all tables in the database.

Parameters

For usage, see Synopsis.

The replica placement policies work as follows:

• DEFAULT (Default): If the replica placement policy is set to DEFAULT, CockroachDB will use its default replica placement settings, which mean that:

  • Data will be placed in as many regions as necessary to ensure your database survival goals are met.
  • You can get fast stale reads from all database regions.

• RESTRICTED: If the replica placement policy is set to RESTRICTED, CockroachDB will constrain replica placement to only those regions where the table has voting replicas (that is, replicas which participate in the Raft quorum). In practice, this means that voting replicas for the table will be constrained to the table's home region. Specifically, for REGIONAL BY TABLE tables, it will only place replicas in the defined region (or the database's primary region); for REGIONAL BY ROW tables, it will only place replicas for each underlying partition in the partition's specified region. Finally, note that:

  • Regional tables with this placement setting will no longer provide "fast stale reads" from other (non-home) regions, since fast stale reads rely on the presence of non-voting replicas.
  • The RESTRICTED replica placement policy is only available for databases with the ZONE survival goal.
  • This setting does not affect how GLOBAL tables work; they will still place replicas in all database regions.

RENAME TO

ALTER DATABASE ... RENAME TO changes the name of a database.

For examples, see Rename database.

Required privileges

To rename a database, the user must be a member of the admin role or must have the CREATEDB parameter set.

Parameters

For usage, see Synopsis.

RESET {session variable}

ALTER DATABASE ... RESET {session variable} resets a session variable for a database to its default value for the client session.

Required privileges

No privileges are required to reset a session setting.

Parameters

For usage, see Synopsis.

Aliases

In CockroachDB, the following are aliases for ALTER DATABASE ... RESET {session variable}:

• ALTER ROLE ALL IN DATABASE ... RESET {session variable}

SET {session variable}

ALTER DATABASE ... SET {session variable} sets the default value of a session variable for all future sessions on the database. This command does not alter the session setting of the current session.

Required privileges

To set the role session variable, the current user must be a member of the admin role, or a member of the target role.

All other session variables do not require privileges to modify.

Parameters

For usage, see Synopsis.

Aliases

In CockroachDB, the following are aliases for ALTER DATABASE ... SET {session variable}:

• ALTER ROLE ALL IN DATABASE ... SET {session variable}

SET PRIMARY REGION

ALTER DATABASE .. SET PRIMARY REGION sets the primary region of a multi-region database.

Secondary regions allow you to define a database region that will be used for failover in the event your primary region goes down. For more information, see Secondary regions.

For examples, see Manage regions.

Required privileges

To add a primary region to a database with no existing regions, the user must have one of the following:

• Membership to the admin role for the cluster.
• Membership to the owner role, or the CREATE privilege, for the database and all tables in the database.

To switch primary regions to a region that has already been added to a database, the user must have membership to the owner role for the database, or have the CREATE privilege on the database.

Parameters

For usage, see Synopsis.

SET SECONDARY REGION

ALTER DATABASE .. SET SECONDARY REGION adds a secondary region to a multi-region database for failover purposes.

If the primary region fails, the secondary region becomes the new primary region. For more information, see Secondary regions.

For examples, see Manage regions.

Required privileges

To add a secondary region to a database, 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.

Parameters

For usage, see Synopsis.

SURVIVE {ZONE,REGION} FAILURE

ALTER DATABASE ... SURVIVE {ZONE,REGION} FAILURE statement sets the survival goal for a multi-region database.

For examples, see Configure survival goals.

Required privileges

The user must be a member of the admin or owner roles, or have the CREATE privilege on the database.

Parameters

For usage, see Synopsis.

Examples

Manage regions

Setup

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

To follow along with the examples in this section, 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 the primary region

Suppose you want to make the database movr a multi-region database.

To add the first region to the database, or to set an already-added region as the primary region, use a SET PRIMARY REGION statement:

ALTER DATABASE movr SET PRIMARY REGION "us-east1";

ALTER DATABASE PRIMARY REGION

Given a cluster with multiple regions, any databases in that cluster that have not yet had their primary regions set will have their replicas spread as broadly as possible for resiliency. When a primary region is added to one of these databases:

• All tables will be REGIONAL BY TABLE in the primary region by default.
• This means that all such tables will have all of their voting replicas and leaseholders moved to the primary region. This process is known as rebalancing.

Add regions to a database

To add more regions to a database that already has at least one region:

ALTER DATABASE movr ADD region "us-west1";

ALTER DATABASE ADD REGION

ALTER DATABASE movr ADD region "europe-west1";

ALTER DATABASE ADD REGION

To view the regions associated with a multi-region database, use a SHOW REGIONS FROM DATABASE statement:

SHOW REGIONS FROM DATABASE movr;

  database |    region    | primary | secondary |  zones
-----------+--------------+---------+-----------+----------
  movr     | us-east1     |    t    |     f     | {b,c,d}
  movr     | europe-west1 |    f    |     f     | {b,c,d}
  movr     | us-west1     |    f    |     f     | {a,b,c}
(3 rows)

Set the secondary region

To set an existing database region (that is not already the primary region) as the secondary region, use the following statement:

ALTER DATABASE movr SET SECONDARY REGION "us-west1";

ALTER DATABASE SET SECONDARY REGION

Now, the "us-west1" region will act as the primary region if the original primary region fails.

Unset the secondary region

To unset an existing database region as the secondary region on a multi-region database, use the DROP SECONDARY REGION statement:

ALTER DATABASE movr DROP SECONDARY REGION;

ALTER DATABASE DROP SECONDARY REGION

Change the existing primary region

To change the primary region to another region in the database, use a SET PRIMARY REGION statement.

ALTER DATABASE movr SET PRIMARY REGION "europe-west1";

ALTER DATABASE PRIMARY REGION

You can only change an existing primary region to a region that has already been added to the database. If you try to change the primary region to a region that is not already associated with a database, CockroachDB will return an error.

Drop a region from a database

To drop a region from a multi-region database, use a DROP REGION statement.

ALTER DATABASE movr DROP REGION "us-east1";

ALTER DATABASE DROP REGION

You cannot drop a region from a multi-region database if:

• The region is set as the primary region, unless it is the last remaining region.
• The region is set as the secondary region. To drop the region, you must first unset the secondary region using DROP SECONDARY REGION.
• The database uses the REGION survival goal and there are only three regions configured on the database.

Manage super regions

Setup

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

To follow along with the examples in this section, 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

Add a super region to a database

To add a super region to a multi-region database, use the ALTER DATABASE ... ADD SUPER REGION statement:

ALTER DATABASE movr ADD SUPER REGION "usa" VALUES "us-east1", "us-west1";

ALTER DATABASE ADD SUPER REGION

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

Drop a super region from a database

To drop a super region from a multi-region database, use a DROP SUPER REGION statement:

ALTER DATABASE movr DROP SUPER REGION "usa";

ALTER DATABASE DROP SUPER REGION

Note that 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.

For example, using the super region that was added in ADD SUPER REGION:

ALTER DATABASE movr DROP REGION "us-west1";

ERROR: region us-west1 is part of super region usa
SQLSTATE: 2BP01
HINT: you must first drop super region usa before you can drop the region us-west1

Configure replication zones

Setup

The following examples use MovR, a fictional vehicle-sharing application, to demonstrate CockroachDB SQL statements. For more information about the MovR example application and dataset, see MovR: A Global Vehicle-sharing App.

To follow along, run cockroach demo with the --geo-partitioned-replicas flag. This command opens an interactive SQL shell to a temporary, 9-node in-memory cluster with the movr database.

$ cockroach demo --geo-partitioned-replicas

Create a replication zone for a database

To control replication for a specific database, use the ALTER DATABASE ... CONFIGURE ZONE statement to define the relevant values (other values will be inherited from the parent zone):

> ALTER DATABASE movr CONFIGURE ZONE USING num_replicas = 5, gc.ttlseconds = 100000;

CONFIGURE ZONE 1

> SHOW ZONE CONFIGURATION FROM DATABASE movr;

     target     |              raw_config_sql
----------------+-------------------------------------------
  DATABASE movr | ALTER DATABASE movr CONFIGURE ZONE USING
                |     range_min_bytes = 134217728,
                |     range_max_bytes = 536870912,
                |     gc.ttlseconds = 100000,
                |     num_replicas = 5,
                |     constraints = '[]',
                |     lease_preferences = '[]'
(1 row)

Edit a replication zone

ALTER DATABASE movr CONFIGURE ZONE USING range_min_bytes = 0, range_max_bytes = 90000, gc.ttlseconds = 89999, num_replicas = 4;

Remove a replication zone

ALTER DATABASE movr CONFIGURE ZONE DISCARD;

Use Zone Config Extensions

The following examples show:

• How to override specific fields of a schema object's zone configs.
• How something like the Secondary regions multi-region abstraction could have been implemented using Zone Config Extensions. For this example, we will call it "Failover regions".
• How to reset a region's Zone Config Extensions.
• How to discard a region's Zone Config Extensions.
• How you could implement super regions.
• How to minimize cross-region write latency.

Setup

The setup described in this section will be used in the following examples.

Start a cluster

Start a cockroach demo cluster as follows:

cockroach demo --global --nodes=9

This gives us a (preloaded) MovR database on a cluster with the following regions, which can be viewed with SHOW REGIONS:

SHOW REGIONS;

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

Make the database multi-region

Next, modify the database to use the multi-region abstractions as follows:

1. Set the primary region using SET PRIMARY REGION.
2. Add the other two regions using ADD REGION.

ALTER DATABASE movr SET PRIMARY REGION "us-east1";

ALTER DATABASE movr ADD REGION "us-west1";

ALTER DATABASE movr ADD REGION "europe-west1";

Override specific fields of a schema object's zone configs

In this example we will configure a multi-region MovR database to update its lease_preferences field.

Setting the primary region to us-east1 during the setup steps added us-east1 to lease_preferences.

SHOW ZONE CONFIGURATION FROM DATABASE movr;

     target     |                                      raw_config_sql
----------------+-------------------------------------------------------------------------------------------
  DATABASE movr | ALTER DATABASE movr CONFIGURE ZONE USING
                |     range_min_bytes = 134217728,
                |     range_max_bytes = 536870912,
                |     gc.ttlseconds = 90000,
                |     num_replicas = 5,
                |     num_voters = 3,
                |     constraints = '{+region=europe-west1: 1, +region=us-east1: 1, +region=us-west1: 1}',
                |     voter_constraints = '[+region=us-east1]',
                |     lease_preferences = '[[+region=us-east1]]'
(1 row)

We will now use ALTER DATABASE ... ALTER LOCALITY to overwrite the lease_preferences field to add us-west1 to the list of regions:

ALTER DATABASE movr ALTER LOCALITY REGIONAL IN "us-east1" CONFIGURE ZONE USING lease_preferences = '[[+region=us-east1], [+region=us-west1]]';

To view the updated zone configs, enter the following statement:

SHOW ZONE CONFIGURATION FROM DATABASE movr;

     target     |                                      raw_config_sql
----------------+-------------------------------------------------------------------------------------------
  DATABASE movr | ALTER DATABASE movr CONFIGURE ZONE USING
                |     range_min_bytes = 134217728,
                |     range_max_bytes = 536870912,
                |     gc.ttlseconds = 90000,
                |     num_replicas = 5,
                |     num_voters = 3,
                |     constraints = '{+region=europe-west1: 1, +region=us-east1: 1, +region=us-west1: 1}',
                |     voter_constraints = '[+region=us-east1]',
                |     lease_preferences = '[[+region=us-east1], [+region=us-west1]]'
(1 row)

The lease_preferences field is now updated to include us-west1.

To remove the changes made in this example, reset the Zone Config Extensions.

Implement super regions

In this example, Zone Config Extensions are used to provide an alternative implementation of super regions, which are useful for data domiciling.

For this example, you need to start a cockroach demo cluster using the following command, which defines the available cluster localities using the --demo-locality flag:

cockroach demo --nodes=9 --demo-locality=region=us-east1:region=us-east1:region=us-central1:region=us-west1:region=europe-west1:region=europe-west1:region=europe-central1:region=europe-east1:region=europe-east1

Next, enter the following statements at the SQL prompt. These statements will:

• Make the movr database into a multi-region database by setting the primary region.
• Set the movr database to survive region failures.
• Add the remaining regions defined at cluster start time to the multi-region movr database (for a total of 6).

ALTER DATABASE movr SET PRIMARY REGION "us-east1";
ALTER DATABASE movr ADD REGION "us-central1";
ALTER DATABASE movr ADD REGION "us-west1";
ALTER DATABASE movr ADD REGION "europe-west1";
ALTER DATABASE movr ADD REGION "europe-central1";
ALTER DATABASE movr ADD REGION "europe-east1";
ALTER DATABASE movr SURVIVE REGION FAILURE;

Now that the multi-region cluster is configured, we will use the following ALTER LOCALITY statements to configure replication zones such that:

• Replicas in the us-east1 region are only stored on nodes in the US.
• Replicas in the europe-central1 region are only stored on nodes in the EU.

ALTER DATABASE movr ALTER LOCALITY REGIONAL IN "us-east1" CONFIGURE ZONE USING
    num_replicas = 7,
    constraints = '{+region=us-east1: 3,
                    +region=us-central1: 3,
                    +region=us-west1: 1}',
    lease_preferences = '[[+region=us-east1], [+region=us-central1]]';

ALTER DATABASE movr ALTER LOCALITY REGIONAL IN "europe-central1" CONFIGURE ZONE USING
    num_replicas = 7,
    constraints = '{+region=europe-central1: 3,
                    +region=europe-west1: 3,
                    +region=europe-east1: 1}',
    lease_preferences = '[[+region=europe-central1], [+region=europe-west1]]';

Minimize cross-region write latency

In this example, Zone Config Extensions are used to minimize cross-region write latency in a cluster with the following characteristics:

• Three main US regions (us-west1,us-east1,us-central1).
• Two additional distant regions (europe-west1, asia-northeast1). Only follower reads will be made from these regions.

To minimize the cross-region write latency, configure replication zones such that the 3 US regions have voting replicas (that is, replicas that participate in Raft quorum). This will leave the 2 additional non-US regions with only non-voting replicas.

For this example, you need to start a cockroach demo cluster using the following command, which defines the available cluster localities using the --demo-locality flag:

cockroach demo --nodes=5 --demo-locality=region=us-east1:region=us-west1:region=us-central1:region=europe-west1:region=asia-northeast1

Next, enter the following statements at the SQL prompt. These statements will:

• Make the movr database into a multi-region database by setting the primary region.
• Set the movr database to survive region failures.
• Add the remaining regions defined at cluster start time to the multi-region movr database (for a total of 5).

ALTER DATABASE movr SET PRIMARY REGION "us-west1";
ALTER DATABASE movr ADD REGION "us-central1";
ALTER DATABASE movr ADD REGION "us-east1";
ALTER DATABASE movr ADD REGION "europe-west1";
ALTER DATABASE movr ADD REGION "asia-northeast1";
ALTER DATABASE movr SURVIVE REGION FAILURE;

By default, all tables in the movr database are REGIONAL tables:

SHOW TABLES;

  schema_name |         table_name         | type  | owner | estimated_row_count |              locality
--------------+----------------------------+-------+-------+---------------------+--------------------------------------
  public      | promo_codes                | table | demo  |                1000 | REGIONAL BY TABLE IN PRIMARY REGION
  public      | rides                      | table | demo  |                 500 | REGIONAL BY TABLE IN PRIMARY REGION
  public      | user_promo_codes           | table | demo  |                   5 | REGIONAL BY TABLE IN PRIMARY REGION
  public      | users                      | table | demo  |                  50 | REGIONAL BY TABLE IN PRIMARY REGION
  public      | vehicle_location_histories | table | demo  |                1000 | REGIONAL BY TABLE IN PRIMARY REGION
  public      | vehicles                   | table | demo  |                  15 | REGIONAL BY TABLE IN PRIMARY REGION
(6 rows)

Now that the multi-region cluster is configured, we will use the following ALTER LOCALITY statements to configure replication zones such that:

• The 3 US regions have voting replicas (that is, replicas that participate in Raft quorum).
• The 2 additional regions (Europe and Japan) are left with only non-voting replicas that can be used to serve follower reads.

ALTER DATABASE movr ALTER LOCALITY REGIONAL CONFIGURE ZONE USING voter_constraints = '{+region=us-west1: 2, +region=us-central1: 2, +region=us-east1: 1}';

Failover regions

In this example we will use Zone Config Extensions to configure a multi-region MovR database so that if the primary region fails, enough replicas will be found in another region (the "failover" region) to take over for the primary region. We will set the locality scope for this configuration to be REGIONAL IN, which covers all REGIONAL BY TABLE IN {region} tables and all {region} partitions of REGIONAL BY ROW tables.

1. Set the database to have a REGION survival goal using ALTER DATABASE ... SURVIVE REGION FAILURE:

    ALTER DATABASE movr SURVIVE REGION FAILURE;
   

2. Apply the REGIONAL BY ROW locality to the movr.rides table using the following statement:

    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";
   

3. View the zone configs for the movr.rides table using SHOW ZONE CONFIGURATION:

    SHOW ZONE CONFIGURATION FROM TABLE movr.rides;
   

         target     |                                      raw_config_sql
    ----------------+-------------------------------------------------------------------------------------------
      DATABASE movr | ALTER DATABASE movr CONFIGURE ZONE USING
                    |     range_min_bytes = 134217728,
                    |     range_max_bytes = 536870912,
                    |     gc.ttlseconds = 90000,
                    |     num_replicas = 5,
                    |     num_voters = 5,
                    |     constraints = '{+region=europe-west1: 1, +region=us-east1: 1, +region=us-west1: 1}',
                    |     voter_constraints = '{+region=us-east1: 2}',
                    |     lease_preferences = '[[+region=us-east1]]'
    (1 row)
   

   Remember that we configured us-east1 to be our primary region during cluster setup. The output above confirms that us-east1 is the primary region based on the values of the voter_constraints and lease_preferences keys.

4. Update the configuration to keep additional voting replicas and leaseholders in us-west1. We do this because we would like to configure us-west1 to be the failover region for us-east1. The following SQL statement accomplishes this by configuring us-east1 to keep additional voting replicas and leaseholders in us-west1. This means that if us-east1 fails, it will fail over to us-west1.

    ALTER DATABASE movr ALTER LOCALITY REGIONAL IN "us-east1" CONFIGURE ZONE USING voter_constraints = '{+region=us-east1: 2, +region=us-west1: 2}', lease_preferences = '[[+region=us-east1], [+region=us-west1]]';
   

5. View the zone configs for the movr.rides table using SHOW ZONE CONFIGURATION:

    SHOW ZONE CONFIGURATION FROM TABLE movr.rides;
   

         target     |                                      raw_config_sql
    ----------------+-------------------------------------------------------------------------------------------
      DATABASE movr | ALTER DATABASE movr CONFIGURE ZONE USING
                    |     range_min_bytes = 134217728,
                    |     range_max_bytes = 536870912,
                    |     gc.ttlseconds = 90000,
                    |     num_replicas = 5,
                    |     num_voters = 5,
                    |     constraints = '{+region=europe-west1: 1, +region=us-east1: 1, +region=us-west1: 1}',
                    |     voter_constraints = '{+region=us-east1: 2, +region=us-west1: 2}',
                    |     lease_preferences = '[[+region=us-east1], [+region=us-west1]]'
    (1 row)
   

   The following changes are shown: - There are now 2 voting replicas stored in us-west1. - There is now a preference that if leases cannot be placed in us-east1, they should be placed in us-west1.

   Both of these changes combine to ensure that if us-east1 goes down, the cluster will still be able to operate until some mitigation is in place.

To remove the zone config changes made in this example, reset the Zone Config Extensions.

Reset a region's Zone Config Extensions

To reset the Zone Config Extension configuration applied to a region to the default settings, enter the following statement:

ALTER DATABASE movr ALTER LOCALITY CONFIGURE ZONE USING DEFAULT;

Discard a region's Zone Config Extensions

To discard the Zone Config Extension settings from a region, enter the following statement:

ALTER DATABASE movr ALTER LOCALITY CONFIGURE ZONE DISCARD;

Change database owner

Setup

The following examples use MovR, a fictional vehicle-sharing application, to demonstrate CockroachDB SQL statements. For more information about the MovR example application and dataset, see MovR: A Global Vehicle-sharing App.

To follow along, run cockroach demo to start a temporary, in-memory cluster with the movr dataset preloaded:

$ cockroach demo

Change a database's owner

Suppose that the current owner of the movr database is root and you want to change the owner to a new user named max.

> ALTER DATABASE movr OWNER TO max;

To verify that the owner is now max, query the pg_catalog.pg_database and pg_catalog.pg_roles tables:

> SELECT rolname FROM pg_catalog.pg_database d JOIN pg_catalog.pg_roles r ON d.datdba = r.oid WHERE datname = 'movr';

  rolname
-----------
  max
(1 row)

Set replica placement policy

Setup

To follow along with the examples below:

1. Start a demo cluster with the --global flag to simulate a multi-region cluster:

   cockroach demo --global --nodes 9
   

2. Set the demo cluster's database regions and table localities as described in Low Latency Reads and Writes in a Multi-Region Cluster (specifically, starting at Step 5. Execute multi-region SQL statements).

3. Enable the replica placement syntax with either the session variable or the cluster setting as shown below.

   1. To use the session variable:

      SET enable_multiregion_placement_policy = on;
      

   2. To use the cluster setting:

      SET CLUSTER SETTING sql.defaults.multiregion_placement_policy.enabled = on;
      

Create a database with the replica placement policy set to restricted

If you know at database creation time that you'd like to set the database's replica placement policy to "restricted", you can do so in a CREATE DATABASE statement as shown below:

CREATE DATABASE movr2 PRIMARY REGION "us-east1" REGIONS "us-west1", "europe-west1" PLACEMENT RESTRICTED;

CREATE DATABASE

Set the replica placement policy to RESTRICTED

When you set the database's placement policy to RESTRICTED, you are saying that you want the underlying data to be restricted to the table or partition's home region.

ALTER DATABASE movr PLACEMENT RESTRICTED;

ALTER DATABASE PLACEMENT

Set the replica placement policy to DEFAULT

If previously you set the replica placement policy to RESTRICTED, you can set it back to the default by issuing the following statement:

ALTER DATABASE movr PLACEMENT DEFAULT;

ALTER DATABASE PLACEMENT

Rename database

Rename a database

> CREATE DATABASE db1;

> SHOW DATABASES;

  database_name
-----------------
  db1
  defaultdb
  movr
  postgres
  system
(5 rows)

> ALTER DATABASE db1 RENAME TO db2;

> SHOW DATABASES;

  database_name
-----------------
  db2
  defaultdb
  movr
  postgres
  system
(5 rows)

Configure survival goals

Survive zone failures

To change the survival goal of a multi-region database to survive zone failures, use the following statement:

ALTER DATABASE {db} SURVIVE ZONE FAILURE;

ALTER DATABASE SURVIVE

For more information about the zone survival goal, see Surviving zone failures.

Survive region failures

To change the survival goal of a multi-region database to survive region failures, use the following statement:

ALTER DATABASE {db} SURVIVE REGION FAILURE;

ALTER DATABASE SURVIVE

If you try to change a database with less than 3 database regions to survive region failures, the following error will be signalled:

ERROR: at least 3 regions are required for surviving a region failure
SQLSTATE: 42602
HINT: you must add additional regions to the database using ALTER DATABASE mr ADD REGION <region_name>

For more information about the region survival goal, see Surviving region failures.

See also

• Multi-Region Capabilities Overview
• Secondary regions
• Super regions
• Zone Config Extensions
• Data Domiciling with CockroachDB
• CREATE DATABASE
• CREATE TABLE
• ALTER TABLE
• Online Schema Changes
• SQL Statements

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