Backstory: I had a debian 11 VPS. I installed the postgresql program from the debian 11 apt repo, back a few months ago. Back then, it was postgres 13 on the debian stable repos.

Fast forward couple months: debian 12 comes out. I do a “apt dist-upgrade” and in-place upgrade my VPS from debian 11 to debian 12. Along with this upgrade, comes postgresql 15 installed.

Now, fast forward couple more months: lemmy 0.18.3 comes out. I do not upgrade (I am on lemmy 0.18.2—afaik).

Fast forward some time, too: lemmy 0.18.4 comes out. I decide to upgrade to 0.18.4 from my existing 0.18.2.

I pull the git repo. Compile it locally. It goes well, no errors in the compilation process. I stop the lemmy systemd service, then I “mv” the compiled “lemmy_server” to /usr/bin dir.

I try to restart the now-upgraded lemmy systemd service. However, the systemd service fails.

I check the sudo journalctl -fu lemmy and I see the following error message:

lemmy_server[17631]: thread 'main' panicked at 'Couldn't run DB Migrations: Failed to run 2023-07-08-101154_fix_soft_delete_aggregates with: syntax error at or near "trigger"', crates/db_schema/src/utils.rs:221:25

I report this issue here: https://github.com/LemmyNet/lemmy/issues/3756#issuecomment-1686439103

However, after a few back and forths and internet search, I conclude that somewhere between lemmy 0.18.3 and 0.18.4, lemmy stops supporting psql <15. So, my existing DB is not compatible.

Upon my investigation on my VPS setup, I concluded that psql 15 is running, however, lemmy is using the psql 13 tables (I do not know if this is the correct term).

Now my question: is there a way to import the lemmy data I had in the psql 13 tables to a new psql 15 table (or database, I don’t know the term).

To make things hairier: I also run a dendrite server on the same VPS, and the dendrite server is using the psql 15 with psql 13 tables on the same database as the lemmy one.

The dendrite database is controlled by a psql user named “dendrite” and the lemmy database is controlled by a psql user named “lemmy” . I hope this makes differentiation between two databases possible. And so I do not harm my existing dendrite database.

Any recommendations about my options here?

  • RoundSparrowM
    1·
    1 year ago

    I can see only one of my Subscribed communities in there, though.

    Ok, what probably happened there was incoming federation triggered it to create the community on your ‘empty’ database. So again, we want to stop lemmy_server service now to try and stop further data going into this empty one.

    • Anark Karabey@monero.townOP
      2·
      1 year ago

      So, what can we do now? It seems like the back’ed up sql data is still in there. As I said, I could see one of the communities I subscribed on the stdout, when I applied your command line speaking the the lemmy backend directly.

      • RoundSparrowM
        2·
        1 year ago

        As I said, I could see one of the communities I subscribed on the stdout

        but only one, right? See federation is kind of automagic in how if one single post came in for that community it could very well go create the community itself. On an empty database.

        Now did you upgrade lemmy-ui and maybe run into problems there?

        I think the safe thing to do at this point is work with postgresql and try to make sense of the data in 15 and deduce why we think Lemmy started as a virgin instance. But it’s going to take some time. And I need to take a couple breaks… I will be around for the next 5 or 6 hours, but need a 15 minute break and then about 30 or 40 minutes break to travel to dinner (but I’ll be online once I arrive).

        pg_dumpall against 15 will give us EVERYTHING - and we grep through that and see if we can figure out if somehow two different databases got created. That’s what I think might have happened. I normally create a half-dozen different databases in 15 for testing federation locally (lemmy-alpha, beta, gamma, etc).

        I guessing the “/lemmy” at the end isn’t exactly how the .config worked prior to us shifting over to the URL scheme.

        • Anark Karabey@monero.townOP
          2·
          1 year ago

          Now did you upgrade lemmy-ui and maybe run into problems there?

          I haven’t updated lemmy-ui yet. I should pull the git repo and compile it.

          And I need to take a couple breaks…

          Yeah, me too. It is quite deep into the night where I am from. I will probably have to do a sleep, and then go about my daily routine tomorrow. I can be online the same hour we started as today.

          • RoundSparrowM
            2·
            1 year ago

            ok if you want to end now, I’ll be around tomorrow too.

            I think we both suspect that the URL vs the config file is using a different database name. And it didn’t see the data we restored and started from scratch.