Migrating databases from Greenplum® to PostgreSQL

You can migrate a database from Greenplum® to the PostgreSQL cluster using Yandex Data Transfer.

To transfer a database from Greenplum® to PostgreSQL:

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:

• Greenplum® cluster fee: Use of computing resources allocated to hosts and disk space (see Yandex MPP Analytics for PostgreSQL pricing).
• Managed Service for PostgreSQL cluster fee: Use of computing resources allocated to hosts and disk space (see Managed Service for PostgreSQL pricing).
• Fee for public IP addresses assigned to cluster hosts (see Virtual Private Cloud pricing).
• Fee per transfer: Use of computing resources and number of transferred data rows (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®-type source endpoint and configure it using the following settings:

   • Connection type: Managed Service for Greenplum cluster
   • Managed Service for Greenplum cluster: <Greenplum®_source_cluster_name> from the drop-down list
   • Database: postgres
   • User: gp-user
   • Password: <user_password>
   • Service object schema: public

2. Create a target endpoint and set up the transfer:

   Manually

   Terraform

   1. Create a PostgreSQL-type target endpoint and specify its cluster connection settings:

      • Installation type: Yandex Managed Service for PostgreSQL cluster
      • Managed Service for PostgreSQL cluster: <PostgreSQL>_target_cluster_name from the drop-down list
      • Database: db1
      • User: pg-user
      • Password: <user_password>

   2. Create a transfer of the Snapshot type that will use the new endpoints.

      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 Snapshot field under Transfer parameters, select Regular and specify the copy interval. The transfer will automatically activate after the specified interval.

      Warning

      Before setting up regular copying, verify that the target endpoint is configured with a DROP or TRUNCATE cleanup policy to prevent data duplication.

   1. In the greenplum-postgresql.tf file, specify the following variables:

      • gp_source_endpoint_id: Source endpoint ID.
      • transfer_enabled: Set to 1 to create a transfer.

   2. Make sure the Terraform configuration files are correct using this command:

      terraform validate
      

      Terraform will show any errors found in your configuration 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.

Activate the transferActivate the transfer

1. Connect to the 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 PostgreSQL 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.public.x_tab;
   

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

Verify replication after reactivationVerify replication after reactivation

1. In the target endpoint parameters, select either DROP or TRUNCATE as cleanup policy.

2. Connect to the Greenplum® cluster.

3. In the x_tab table, delete the row with the 41 ID and update the one with the 42 ID:

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

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

5. Check the changes in the x_tab table of the PostgreSQL target:

   SELECT id, name FROM db1.public.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. Delete the resources you no longer need to avoid paying for them:

• Make sure the transfer status is Completed, upon which you can delete the transfer.

• Delete both the source and target endpoints.

• Delete the clusters:

  Manually

  Terraform

  • Managed Service for PostgreSQL.
  • Yandex MPP Analytics for PostgreSQL.

  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.