add postgres upgrade post

content/posts/upgrade-postgres-docker/index.md

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+---
+title: "Upgrade PostgreSQL in Docker"
+date: 2023-08-17T22:52:07+02:00
+draft: false
+tags: ["postgres", "postgresql", "docker", "upgrade", "self-hosting", "database"]
+
+# Keep them short
+summary: "Upgrading postgresql can't be done in-place, so here's a scripted version to help you do so."
+
+cover:
+  image: "elephant.jpg"
+  relative: true
+  alt: "Trumpeting elephant"
+  caption: "Trumpeting elephant (Muhammad Mahdi Karim, GFDL 1.2)"
+  hidden: false  # applies only on single view
+
+#showToc: true
+#TocOpen: false
+---
+
+Upgrading postgresql can't be done in-place, you have to setup a new DB with the expected version and restore your content in this DB.
+
+I had a few containers running older versions of postgres lying around (13 and 14), and I wanted to upgrade them to postgresql 15. Here's the script I came up with.
+
+{{< note class="warning" title="⚠️ Warning" >}}
+When handling production data, don't blindly run this as a script. Run each step manually and double-check that you aren't destroying anything.
+{{< /note >}}
+
+{{< note class="info" >}}
+This post is inspired by [Thomas Bandt's](https://thomasbandt.com/postgres-docker-major-version-upgrade), with some tweaks in the process, and less writing.
+{{< /note >}}
+
+```bash
+app_name="app"
+db_user="user"
+db_name="db"
+
+# Stop the running app(s)
+# to prevent modifications during the backup & restore
+docker compose stop $app_name
+
+# Dump DB & roles
+# I'm using custom scripts for this part in order to run
+# them regularly and export the backups.
+# Here's what they basically do.
+docker compose exec -it db \
+  pg_dump -Fc -U $db_user $db_name > ./db_export/backup.dump
+docker compose exec -it db \
+  pg_dumpall --globals-only -U $db_user > ./db_export/roles.sql
+
+# Shutdown everything
+docker compose down
+
+# Move current data dir, don't remove it yet
+mv db_data db_data_OLD
+
+# edit docker-compose.yaml - upgrade psql
+vim docker-compose.yaml
+
+# Up the new database & check version
+docker compose up -d db
+docker compose exec -it db psql -U $db_user -c 'select version();'
+
+# Restore roles
+# Skip for simple DB where only 1 user,
+# managed by the docker image, is used
+docker compose cp ./db_export/roles.sql db:/tmp/roles
+docker compose exec -it db psql -U $db_user -d $db_name -f /tmp/roles
+
+# Restore content
+docker compose cp ./db_export/backup.dump db:/tmp/backup
+docker compose exec -it db pg_restore -U $db_user -d $db_name /tmp/backup
+
+# Check if content is properly restored:
+# list tables, make a few queries
+docker compose exec -it db psql -U $db_user -d $db_name -c "\dt"
+
+# Launch app again
+docker compose up -d
+docker compose logs -ft
+
+# check app still works and has data
+
+# Finally remove the old data dir
+rm -rf db_data_OLD
+```
+
+{{<unsafe>}}
+<small>
+Postgres, PostgreSQL and the Slonik Logo are trademarks or registered trademarks of the PostgreSQL Community Association of Canada, and used with their permission.
+</small>
+{{</unsafe>}}