How to upgrade PostgreSQL from 14 to 15 with brew?

I was struggling figuring out how to upgrade the Postgresql with brew on my machine, so I compiled my learnings. Here is a quick tutorial.

Install postgresql@15

Make sure you have both postgresql@14 and postgresql@15 installed.

brew search postgres
brew install postgresql@15

Fix executables

postgresql@15 is keg-only, which means it was not symlinked into /opt/homebrew.

Let’s put it into our path:

echo 'export PATH="/opt/homebrew/opt/postgresql@15/bin:$PATH"' >> ~/.zshrc
source ~/.zshrc

Stop running services

Stop PostgreSQL services from running:

brew services list
brew services stop postgresql@14
brew services stop postgresql@15

Migrate the data

Use pg_upgrade executable to migrate the data.

pg_upgrade \
  -d /opt/homebrew/var/postgresql@14 \
  -D /opt/homebrew/var/postgresql@15 \
  -b /opt/homebrew/opt/postgresql@14/bin/ \
  -B /opt/homebrew/opt/postgresql@15/bin/

Note: data migration might fail due to locale issues.

The error would look like:

FATAL:  postmaster became multithreaded during startup
HINT:  Set the LC_ALL environment variable to a valid locale.

To fix it, run:

echo 'export LC_ALL="en_US.UTF-8"' >> ~/.zshrc
source ~/.zshrc

Delete Old data

Delete the old cluster data files:

./delete_old_cluster.sh

Remove PostgreSQL 14

Hopefully, everything went smooth up to this point and we can go ahead and uninstall the old Postgres.

brew uninstall postgresql@14

We are done!

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