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Loading data from YDB to a ClickHouse® data mart

Written by
Updated at February 18, 2026

Data Transfer enables you to transfer data from a database in Managed Service for YDB to a Managed Service for ClickHouse® cluster.

To transfer data:

  1. Prepare your test data.
  2. Set up and activate the transfer.
  3. Test your transfer.

If you no longer need the resources you created, delete them.

  • Managed Service for YDB database (see Managed Service for YDB pricing). Its cost depends on the deployment mode:

    • In serverless mode, you pay for data operations as well as the amount of stored data and backups.
    • In dedicated instance mode, you pay for the use of computing resources allocated to the database, storage size, and backups.

  • Managed Service for ClickHouse® cluster, which includes computing resources allocated to hosts, storage and backup size (see Managed Service for ClickHouse® pricing).

  • Public IP addresses if public access is enabled for cluster hosts (see Virtual Private Cloud pricing).

Getting started

Set up your infrastructure:

  1. Create a Managed Service for YDB database named ydb1 of your preferred configuration.

  2. Create a Managed Service for ClickHouse® cluster of any suitable configuration with publicly accessible hosts and the following settings:

    • DB name: db1
    • Username: user1

    Note

    Public access to cluster hosts is required if you plan to connect to the cluster via the internet. This connection option is simpler and is recommended for the purposes of this guide. You can connect to non-public hosts as well but only from Yandex Cloud virtual machines located in the same cloud network as the cluster.

  3. If using security groups, make sure they are configured correctly and allow connections to your Managed Service for ClickHouse® cluster.

  4. Create a service account named ydb-account with the ydb.editor role. The transfer will use it to access the database.

  1. If you do not have Terraform yet, install it.

  2. Get the authentication credentials. You can add them to environment variables or specify them later in the provider configuration file.

  3. Configure and initialize a provider. There is no need to create a provider configuration file manually, you can download it.

  4. Place the configuration file in a separate working directory and specify the parameter values. If you did not add the authentication credentials to environment variables, specify them in the configuration file.

  5. Download the ydb-to-clickhouse.tf configuration file to the same working directory.

    This file describes:

    • Network.
    • Subnet.
    • Security group and rules for internet access to the Managed Service for ClickHouse® cluster.
    • Managed Service for YDB database.
    • Target Managed Service for ClickHouse® cluster.
    • Source endpoint.
    • Target endpoint.
    • Transfer.

  6. In the ydb-to-clickhouse.tf file, specify the following settings:

    • mch_version: ClickHouse® version.
    • mch_password: ClickHouse® database owner password.

  7. Validate your Terraform configuration files using this command:

    terraform validate

    Terraform will display any configuration errors detected in your files.

  8. Create the required infrastructure:

    1. Run this command to view the planned changes:

      terraform plan

      If you described the configuration correctly, the terminal will display a list of the resources to update and their parameters. This is a verification step that does not apply changes to your resources.

    2. If everything looks correct, apply the changes:

      1. Run this command:

        terraform apply

      2. Confirm updating the resources.

      3. Wait for the operation to complete.

    All the required resources will be created in the specified folder. You can check resource availability and their settings in the management console.

Prepare your test data

  1. Connect to the Managed Service for YDB database.

  2. Create a row-oriented table named table1 with the following columns:

    Name Type Primary key
    Id Int64 Yes
    Name Utf8

    You can create this table using the following SQL query:

    CREATE TABLE table1 (
    Id Int64,
    Name Utf8,
    PRIMARY KEY (Id)
)

  3. Populate the table with data using the following SQL query:

    INSERT INTO table1 (Id, Name)
VALUES
    (1, "Anna"),
    (2, "Robert"),
    (3, "Umar"),
    (4, "Algul"),
    (5, "Viktor");

Set up and activate the transfer

  1. Create a source endpoint of the YDB type with the following database connection settings:

    • Connection settings:

      • Database: Select the Managed Service for YDB database from the list.

      • Service account ID: Select the ydb-account service account.

    • Included paths list: table1.

  2. Create a target endpoint of the ClickHouse® type with the following cluster connection settings:

    • Connection type: Managed cluster.
    • Managed cluster: <ClickHouse®_target_cluster_name> from the drop-down list.
    • Database: db1.
    • User: user1.
    • Password: <user_password>.

  3. Create a transfer of the Snapshot and replication type that will use the endpoints you created.

  4. Activate the transfer and wait for its status to change to Replicating.

  1. In the ydb-to-clickhouse.tf file, set transfer_enabled to 1.

  2. Validate your Terraform configuration files using this command:

    terraform validate

    Terraform will display any configuration errors detected in your files.

  3. Create the required infrastructure:

    1. Run this command to view the planned changes:

      terraform plan

      If you described the configuration correctly, the terminal will display a list of the resources to update and their parameters. This is a verification step that does not apply changes to your resources.

    2. If everything looks correct, apply the changes:

      1. Run this command:

        terraform apply

      2. Confirm updating the resources.

      3. Wait for the operation to complete.

    The transfer will be activated automatically upon creation.

Test your transfer

Make sure the transfer works correctly by testing copying and replication.

Test copying

  1. Connect to the db1 database in the Managed Service for ClickHouse® target cluster.

  2. Run this query:

    SELECT * FROM db1.table1;
    Response example
    # | Id  | Name     | __data_transfer_commit_time | __data_transfer_delete_time
--+-----+----------+-----------------------------+----------------------------
1 | "1" | "Anna"   | "1722023098109014844"       | "0"
2 | "2" | "Robert" | "1722023098109014844"       | "0"
3 | "3" | "Umar"   | "1722023098109014844"       | "0"
4 | "4" | "Algul"  | "1722023098109014844"       | "0"
5 | "5" | "Viktor" | "1722023098109014844"       | "0"

Test replication

  1. Connect to the Managed Service for YDB database.

  2. Add data to the table named table1:

    INSERT INTO table1 (Id, Name)
VALUES
    (6, "Maria"),
    (7, "Alex");

  3. Check that the data has been replicated to the target database:

    1. Connect to the db1 database in the Managed Service for ClickHouse® target cluster.

    2. Run this query:

      SELECT * FROM db1.table1;
      Response example
      # | Id  | Name     | __data_transfer_commit_time | __data_transfer_delete_time
--+-----+----------+-----------------------------+----------------------------
1 | "1" | "Anna"   | "1722023098109014844"       | "0"
2 | "2" | "Robert" | "1722023098109014844"       | "0"
3 | "3" | "Umar"   | "1722023098109014844"       | "0"
4 | "4" | "Algul"  | "1722023098109014844"       | "0"
5 | "5" | "Viktor" | "1722023098109014844"       | "0"
6 | "6" | "Maria"  | "1722023655224000000"       | "0"
7 | "7" | "Alex"   | "1722023655225000000"       | "0"

Delete the resources you created

Note

Before deleting the resources, deactivate the transfer.

To reduce the consumption of resources, delete those you do not need:

  1. In the terminal window, go to the directory containing the infrastructure plan.

    Warning

    Make sure the directory has no Terraform manifests with the resources you want to keep. Terraform deletes all resources that were created using the manifests in the current directory.

  2. Delete resources:

    1. Run this command:

      terraform destroy

    2. Confirm deleting the resources and wait for the operation to complete.

    All the resources described in the Terraform manifests will be deleted.

ClickHouse® is a registered trademark of ClickHouse, Inc.

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