AWS RDS PostgreSQL Upgrade from 9.6.22 to 10.17

Question

Good day. I just finished upgrading my AWS RDS database engine from 9.6.22 to 10.17. I used these steps to make the upgrade using the AWS Console:

1. Create snapshot of target database to upgrade
2. Restore snapshot
3. Upgrade the restored snapshot's (which is now a new instance) DB Engine version.

After I did all of this, everything seems fine but when I access the database, this warning message appears

WARNING: psql major version 9.6, server major version 10.
     Some psql features might not work.

I did not continue on my testing because I want to know what is the meaning of this first. Because I am fairly new in AWS as a whole. Thanks!

Answer 1

The meaning is that just because you are connecting to an upgraded database on some machine run by Amazon, the PostgreSQL installation on your local machine was not magically updated. psql from version 9.6 doesn't know what metadata tables were changed in v10, what features were removed and so on.

It would be a good idea to install a more recent version of PostgreSQL on your machine. By the way, upgrading to v10 was not the smartest move, as that version will go out of support in less than a year. You should upgrade to the latest version that your service provider offers.

Answer 2

The client program psql you are using to connect to the database is from an older version than the database it is connecting to. Some of the introspection features might not work. For example, psql from 9.6 won't know how to do tab completion for commands that were added to the server after 9.6.

This is generally not a major problem for psql (unless the server wants to use SCRAM authentication), but for optimal experience it would be good to install a newer client. Other tools like pg_dimp might not with at all against a server newer than they are.