Migrating databases from Greenplum® to ClickHouse®

You can migrate a database from Greenplum® to ClickHouse® using Yandex Data Transfer.

To transfer a database from Greenplum® to ClickHouse®:

1. Set up your transfer.
2. Activate the transfer.
3. Verify replication after reactivation.

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

Required paid resourcesRequired paid resources

The support cost for this solution includes:

• Managed Service for Greenplum® cluster fee: Covers the use of computational resources allocated to hosts and disk storage (see Managed Service for Greenplum® pricing).

• Managed Service for ClickHouse® cluster fee: Covers the use of computational resources allocated to hosts (including ZooKeeper hosts) and disk storage (see Managed Service for ClickHouse® pricing).

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

• Transfer fee: Based on computational resource consumption and the total number of data rows transferred (see Data Transfer pricing).

Getting startedGetting started

In our example, we will create all required resources in Yandex Cloud. Set up the infrastructure:

Set up your transferSet up your transfer

1. Create a Greenplum® source endpoint and specify its cluster connection settings.

2. Create a Snapshot transfer that uses endpoints for the source and target.

   While real-time replication is not supported for this endpoint pair, you can configure regular copying while creating the transfer. To do this, in the Transfer parameters field under Snapshot, select Regular and specify the copy interval. The transfer will automatically activate after the specified interval.

Activate the transferActivate the transfer

1. Connect to the Managed Service for Greenplum® cluster, create a table named x_tab, and populate it with data:

   CREATE TABLE x_tab
   (
       id NUMERIC,
       name CHARACTER(5)
   );
   CREATE INDEX ON x_tab (id);
   INSERT INTO x_tab (id, name) VALUES
   (40, 'User1'),
   (41, 'User2'),
   (42, 'User3'),
   (43, 'User4'),
   (44, 'User5');
   

2. Activate the transfer and wait for its status to change to Completed.

3. To verify the data transfer, connect to the Managed Service for ClickHouse® target cluster and check whether the columns of the x_tab table in the db1 database match those of the x_tab table in the source database:

   SELECT id, name FROM db1.x_tab;
   

   ┌─id─┬─name──┐
   │ 40 │ User1 │
   │ 41 │ User2 │
   │ 42 │ User3 │
   │ 43 │ User4 │
   │ 44 │ User5 │
   └────┴───────┘
   

Test the copy function upon re-activationTest the copy function upon re-activation

1. Connect to the Managed Service for Greenplum® cluster; in the x_tab table, delete one row and update one:

   DELETE FROM x_tab WHERE id = 41;
   UPDATE x_tab SET name = 'Key3' WHERE id = 42;
   

2. Reactivate the transfer and wait for its status to change to Completed.

3. Check the changes in the x_tab table of the ClickHouse® target:

   SELECT id, name FROM db1.x_tab;
   

   ┌─id─┬─name──┐
   │ 42 │ Key3  │
   │ 40 │ User1 │
   │ 43 │ User4 │
   │ 44 │ User5 │
   └────┴───────┘
   

Delete the resources you createdDelete the resources you created

Some resources incur charges. To avoid paying for them, delete the resources you no longer need:

1. Make sure the transfer has the Completed status and delete it.

2. Delete the source endpoint.

3. Delete other resources using the method matching their creation method:

   Manually

   Terraform

   1. Delete the Managed Service for ClickHouse® cluster.
   2. Delete the Managed Service for Greenplum® cluster.
   3. Delete the target endpoint.

   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.