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?

  • @k4r4b3y@monero.townOP
    2•1 year ago

    Here it is:

    $ cat /etc/lemmy/lemmy.hjson
{
  database: {
    # put your db-passwd from above
    password: "REDACTED"
  }
  # replace with your domain
  hostname: hostname.tld
  bind: "127.0.0.1"
  federation: {
    enabled: true
  }
  # remove this block if you don't require image hosting
  pictrs: {
    url: "http://localhost:8080/"
  }
}

    I redacted the password, and the hostname entries.

    • RoundSparrowM
      1•1 year ago

      you don’t have a port number specified in lemmy.json it is either using the default value or you have LEMMY_DATABASE_URL set?

      Do you have an environment variable: LEMMY_DATABASE_URL in your lemmy_server service config or otherwise?

      Lookibg at the Rust source code, there is a comment that says “// The env var should override anything in the settings config”

      • @k4r4b3y@monero.townOP
        2•1 year ago

        I think my setup is using the default value.

        I do not see me specifying the LEMMY_DATABASE_URL in my systemd file:

        $ cat /etc/systemd/system/lemmy.service
[Unit]
Description=Lemmy - A link aggregator for the fediverse
After=network.target

[Service]
User=lemmy
ExecStart=/usr/bin/lemmy_server
Environment=LEMMY_CONFIG_LOCATION=/etc/lemmy/lemmy.hjson
# remove these two lines if you don't need pict-rs
Environment=PICTRS__SERVER__ADDR=127.0.0.1:8080
Environment=PICTRS__STORE__PATH=/var/lib/pictrs/files
Environment=PICTRS__REPO__PATH=/var/lib/pictrs/repo
Restart=on-failure

# Hardening
ProtectSystem=yes
PrivateTmp=true
MemoryDenyWriteExecute=true
NoNewPrivileges=true

[Install]
WantedBy=multi-user.target
        • RoundSparrowM
          1•1 year ago

          I do not see me specifying the LEMMY_DATABASE_URL in my systemd file:

          ok, so you have a choice… we have to figure out the syntax of the port number in config file, or you introduce a LEMMY_DATABASE_URL in your lemmy.service file.

          • @k4r4b3y@monero.townOP
            2•1 year ago

            I would go with introducing LEMMY_DATABASE_URL in my lemmy.service file. However, is doing that going to expose my lemmy database password to the lemmy.service file?

            • RoundSparrowM
              1•1 year ago

              yes, the password will need to be in the LEMMY_DATABASE_URL… but a lemmy.service should be secure… ? I mean it’s kind of thing the system using during boot.

              • @k4r4b3y@monero.townOP
                2•1 year ago

                but a lemmy.service should be secure…

                yeah it is secure, as the root user password is required to do anything with that file. Alright, let’s do this.

                • RoundSparrowM
                  2•1 year ago

                  So the next step is the backup, did you do the backup of lemmy data from 13? And spot-check that it looks like your data?

                  • @k4r4b3y@monero.townOP
                    2•1 year ago
                    user@server:~$ sudo -iu postgres /usr/lib/postgresql/15/bin/pg_dump --port=5432 lemmy > /home/user/lemmy_databackup.sql
user@server:~$ ls -la lemmy_databackup.sql
-rw-r--r-- 1 user user 56554817 Aug 23 00:59 lemmy_databackup.sql
user@server:~$ ls -lah lemmy_databackup.sql
-rw-r--r-- 1 user user 54M Aug 23 00:59 lemmy_databackup.sql