Exporting Greenplum® data to cold storage in Yandex Object Storage

Yandex Managed Service for Greenplum® data is stored on cluster disks. With a Yandex Cloud Yezzey extension, you can move this data to a cold storage in Yandex Object Storage. This way, it will be stored in a service bucket in a compressed and encrypted form. It is a convenient option if you need to store your data for a long time without using it much. This will make data storage less costly.

Yezzey supports append-optimized (AO) and append-optimized column-oriented (AOCO) tables. For more information about the tables, see Data storage types and the Greenplum® documentation.

To transfer your data from Managed Service for Greenplum® cluster disks to a cold storage in Object Storage:

1. Transfer a Greenplum® table to Object Storage.
2. Check the result.

You can also transfer your data back to cluster disks.

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

Getting startedGetting started

1. Create a Managed Service for Greenplum® cluster. When creating a cluster, make sure to enable Hybrid storage.

   Note

   You cannot disable this option after you save your cluster settings.

2. Get an SSL certificate to connect to the Greenplum® database:

   Linux (Bash)/macOS (Zsh)

   Windows (PowerShell)

   mkdir -p ~/.postgresql && \
   wget "https://storage.yandexcloud.net/cloud-certs/CA.pem" \
        --output-document ~/.postgresql/root.crt && \
   chmod 0655 ~/.postgresql/root.crt
   

   The certificate will be saved to the ~/.postgresql/root.crt file.

   mkdir $HOME\.postgresql; curl.exe -o $HOME\.postgresql\root.crt https://storage.yandexcloud.net/cloud-certs/CA.pem
   

   The certificate will be saved to the $HOME\.postgresql\root.crt file.

   To use graphical IDEs, save a certificate to a local folder and specify the path to it in the connection settings.

Export the Greenplum® table to Object StorageExport the Greenplum® table to Object Storage

1. Connect to the cluster:

   psql "host=c-<cluster_ID>.rw.mdb.yandexcloud.net \
         port=6432 \
         sslmode=verify-full \
         dbname=postgres \
         user=<username> \
         target_session_attrs=read-write"
   

2. Create a database named db_with_yezzey:

   CREATE DATABASE db_with_yezzey;
   

   The new DB will be granted permissions to install extensions. These permissions are not granted for the default DB.

3. Connect to the new DB:

   \connect db_with_yezzey
   

4. Create a Yezzey extension:

   CREATE EXTENSION yezzey;
   

5. Create an append-optimized table named ao_table:

   CREATE TABLE ao_table (a int)
       WITH (appendoptimized=true)
       DISTRIBUTED BY (a);
   

6. Populate the table with a series of integers from 1 through 10,000:

   INSERT INTO ao_table SELECT * FROM GENERATE_SERIES(1, 10000);
   

7. Transfer the ao_table data to a cold storage in Object Storage:

   SELECT yezzey_define_offload_policy('ao_table');
   

Check the resultCheck the result

1. Check how much of the cluster local cache and Object Storage space is used by:

   • Your ao_table:

     SELECT * FROM yezzey_offload_relation_status('ao_table');
     

   • Each segment file in ao_table:

     SELECT * FROM yezzey_offload_relation_status_per_filesegment('ao_table');
     

   If there are non-zero values in each external_bytes column in the command output, the table is transferred to a cold storage in Object Storage.

2. Check which table segment files are now in Object Storage:

   SELECT * FROM yezzey_relation_describe_external_storage_structure('ao_table');
   

3. Make sure the data can be read from Object Storage:

   SELECT AVG(a) FROM ao_table;
   

   Result:

             avg          
   -----------------------
    5000.5000000000000000
   (1 row)
   

4. Make sure the data can be written to Object Storage:

   1. Add a series of integers from 1 through 10,000 to your ao_table:

      INSERT INTO ao_table SELECT * FROM GENERATE_SERIES(1, 10000);
      

   2. Check that the number of rows has doubled:

      SELECT COUNT(1) FROM ao_table;
      

      Result:

       count
      -------
       20000
      (1 row)
      

Transfer the table from Object Storage to cluster disksTransfer the table from Object Storage to cluster disks

To transfer your ao_table from Object Storage back to the Managed Service for Greenplum® cluster disks, run the command below:

SELECT yezzey_load_relation('ao_table');

Delete the resources you createdDelete the resources you created

If you no longer need the cluster you created, delete it.

Greenplum® and Greenplum Database® are registered trademarks or trademarks of VMware, Inc. in the United States and/or other countries.