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?