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How to move psql database from 13 to 15 for lemmy 0.18.4 (monero.town)

submitted 1 year ago by [email protected] to c/[email protected]

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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?

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[–] [email protected] 1 points 1 year ago (1 children)

How do we transform this line so that it fits into the lemmy.hjson file?

We don't... your lemmy.hjson you were using for 0.18.2 - if you used the same password, the only thing we need to do is add the port to 5433... the URL doesn't need to go into that file

[–] [email protected] 2 points 1 year ago (1 children)

if you used the same password

Yes, I used the same psql password.

OK. Then, I am going to remove the

Environment=LEMMY_DATABASE_URL=postgres://lemmy:[email protected]:5433/lemmy

line from the lemmy.service file. And then, I will add the port directive.

The updated /etc/lemmy/lemmy.hjson file is as follows now:

{
  database: {
    # put your db-passwd from above
    password: "REDACTED"
    port: 5433
  }
  # replace with your domain
  hostname: domain.tld
  bind: "127.0.0.1"
  federation: {
    enabled: true
  }
  # remove this block if you don't require image hosting
  pictrs: {
    url: "http://localhost:8080/"
  }
}

observe that I have added the port: 5433 to the database: clause.

[–] [email protected] 2 points 1 year ago

yep, looks good. We will find out if the two formats talk to different data ("DATABASE" within PostgreSQL 15)