Migrating a database 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. Test the copy function upon re-activation.

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

Required paid resourcesRequired paid resources

The support cost includes:

• Managed Service for Greenplum® cluster fee: Using computing resources allocated to hosts and disk space (see Managed Service for Greenplum® pricing).
• Managed Service for PostgreSQL cluster fee: Using computing resources allocated to hosts and disk space (see Managed Service for PostgreSQL pricing).
• Fee for using public IP addresses for cluster hosts (see Virtual Private Cloud pricing).
• Per-transfer fee: Using computing resources and the number of transferred data rows (see Data Transfer pricing).

Getting startedGetting started

For clarity, we will create all required resources in Yandex Cloud. Set up your infrastructure:

Set up your transferSet up your transfer

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

   • 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 transfer:

   Manually

   Terraform

   1. Create a target endpoint of the PostgreSQL type and specify the cluster connection settings in it:

      • 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 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.

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

      • gp_source_endpoint_id: ID of the source endpoint.
      • transfer_enabled: 1 to create a transfer.

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

      terraform validate
      

      If there are any errors in the configuration files, Terraform will point them out.

   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 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 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 │
   └────┴───────┘
   

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

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

2. Connect to the Managed Service for 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. 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 PostgreSQL.
  • 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.