Loading data from Greenplum® to a ClickHouse® data mart

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

To transfer a database from Greenplum® to ClickHouse®:

1. Set up the transfer.
2. Activate the transfer.
3. Check the copy function upon re-activation.

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

Getting startedGetting started

For clarity, we will create all required resources in Yandex Cloud. Prepare the infrastructure:

Set up the transferSet up the transfer

1. Create a source endpoint of the Greenplum® type, and specify the cluster connection settings in it.

2. Create a target endpoint of the ClickHouse type.

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

   Replication is not available for this endpoint pair, but you can set up regular copying when creating a transfer. To do this, in the Snapshot field under Transfer parameters, select Regular and specify the copy interval. This will activate a transfer automatically after the specified time interval.

   Warning

   Before configuring regular copying, make sure the target endpoint parameters idicate either a Drop or a Truncate cleanup policy. Otherwise, data on the target will be duplicated.

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 check that the data was transferred correctly, connect to the Managed Service for ClickHouse® target cluster and make sure that 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 │
   └────┴───────┘
   

Check the copy function upon re-activationCheck 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 are not free of charge. To avoid paying for them, delete the resources you no longer need:

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

• Delete both the source endpoint and the target endpoint.

• Delete the clusters:

  Manually

  Terraform

  • Managed Service for ClickHouse®.
  • Managed Service for Greenplum®.

  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.