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 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 parameters 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 a transfer:

   Manually

   Terraform

   1. Create a target endpoint of the PostgreSQL type and specify the cluster connection parameters 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 the command to view planned changes:

         terraform plan
         

         If the resource configuration descriptions are correct, the terminal will display a list of the resources to modify and their parameters. This is a test step. No resources are updated.

      2. If you are happy with the planned changes, apply them:

         1. Run the command:

            terraform apply
            

         2. Confirm the update of 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 │
   └────┴───────┘
   

Check the copy function upon re-activationCheck 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®.

  If you created your resources using Terraform:

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

  2. Delete the greenplum-postgresql.tf configuration file.

  3. 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.

  4. Confirm updating the resources.

     1. Run the command to view planned changes:

        terraform plan
        

        If the resource configuration descriptions are correct, the terminal will display a list of the resources to modify and their parameters. This is a test step. No resources are updated.

     2. If you are happy with the planned changes, apply them:

        1. Run the command:

           terraform apply
           

        2. Confirm the update of resources.

        3. Wait for the operation to complete.

     All the resources described in the greenplum-postgresql.tf configuration file will be deleted.