Bringing PGDATA physically may lead to corrupted indexes due to glibc version changes. 16.04 -> 18.04 shouldn't cause it, but it may. You can check btree index with amcheck and GIN indexes with a patched version of it (some backporting would be needed). You can find examples here: https://gitlab.com/-/snippets/2001962
But back to the question, if you do dump/restore, indexes will be freshly created, on new machine - therefore there is no question about corruption for them. I'd choose this path in your situation.
On Thu, Sep 2, 2021 at 10:38 AM Vano Beridze <vanuatoo@gmail.com> wrote:
Hello,
I've got 2 VMs with Postgresql 9.5 cluster with streaming replication.
VMs have Ubuntu 16.04.
I would like to upgrade Ubuntu and Postgresql to newer versions.
Ubuntu 16.04 supports upgrading to 18.04.
What is the safest way to upgrade Postgresql cluster along with it?
The database is not big and I can afford completely shutdown the cluster during the upgrade.