I wanted to point out some straightforward commands for doing this database upgrade on your Mac, if you, like me, have ignored doing so. This post from Olivier Lacan was a great help and I just wanted to make it even clearer that it's this easy:
brew services stop postgresql brew postgresql-upgrade-database brew services start postgresql
Glorious! Here's what the original error looked like for me, for SEO juice and future reference:
💚 pg_ctl -D /usr/local/var/postgres start waiting for server to start....2021-01-17 17:03:03.686 EST  FATAL: database files are incompatible with server 2021-01-17 17:03:03.686 EST  DETAIL: The data directory was initialized by PostgreSQL version 12, which is not compatible with this version 13.1. stopped waiting pg_ctl: could not start server Examine the log output
So, I ran the above commands - here's the full output in case you're curious.
💚 brew services stop postgresql Stopping `postgresql`... (might take a while) ==> Successfully stopped `postgresql` (label: homebrew.mxcl.postgresql) 💚 brew postgresql-upgrade-database ==> brew install postgresql@12 ==> Downloading https://homebrew.bintray.com/bottles/postgresql%4012-12.5.big_sur.bottle.tar.gz ==> Downloading from https://d29vzk4ow07wi7.cloudfront.net/6e1717130028267c3f8c3910e10909fde608892da4af2669842da0dca386392a?response-content-disposition=attac ######################################################################## 100.0% ==> Pouring email@example.com_sur.bottle.tar.gz ==> /usr/local/Cellar/postgresql@12/12.5/bin/initdb --locale=C -E UTF-8 /usr/local/var/postgresql@12 ==> Caveats Previous versions of this formula used the same data directory as the regular PostgreSQL formula. This causes a conflict if you try to use both at the same time. In order to avoid this conflict, you should make sure that the postgresql@12 data directory is located at: /usr/local/var/postgresql@12 This formula has created a default database cluster with: initdb --locale=C -E UTF-8 /usr/local/var/postgresql@12 For more details, read: https://www.postgresql.org/docs/12/app-initdb.html postgresql@12 is keg-only, which means it was not symlinked into /usr/local, because this is an alternate version of another formula. If you need to have postgresql@12 first in your PATH run: echo 'export PATH="/usr/local/opt/postgresql@12/bin:$PATH"' >> /Users/qrush/.bash_profile For compilers to find postgresql@12 you may need to set: export LDFLAGS="-L/usr/local/opt/postgresql@12/lib" export CPPFLAGS="-I/usr/local/opt/postgresql@12/include" For pkg-config to find postgresql@12 you may need to set: export PKG_CONFIG_PATH="/usr/local/opt/postgresql@12/lib/pkgconfig" To have launchd start postgresql@12 now and restart at login: brew services start postgresql@12 Or, if you don't want/need a background service you can just run: pg_ctl -D /usr/local/var/postgres@12 start ==> Summary 🍺 /usr/local/Cellar/postgresql@12/12.5: 3,224 files, 41.6MB ==> Upgrading postgresql data from 12 to 13... waiting for server to start....2021-01-17 17:06:21.437 EST  LOG: starting PostgreSQL 12.5 on x86_64-apple-darwin20.1.0, compiled by Apple clang version 12.0.0 (clang-1184.108.40.206), 64-bit 2021-01-17 17:06:21.439 EST  LOG: listening on IPv6 address "::1", port 5432 2021-01-17 17:06:21.439 EST  LOG: listening on IPv4 address "127.0.0.1", port 5432 2021-01-17 17:06:21.440 EST  LOG: listening on Unix socket "/tmp/.s.PGSQL.5432" 2021-01-17 17:06:21.477 EST  LOG: database system was shut down at 2021-01-01 20:11:19 EST 2021-01-17 17:06:21.484 EST  LOG: database system is ready to accept connections done server started waiting for server to shut down....2021-01-17 17:06:21.900 EST  LOG: received fast shutdown request 2021-01-17 17:06:21.900 EST  LOG: aborting any active transactions 2021-01-17 17:06:21.901 EST  LOG: background worker "logical replication launcher" (PID 14874) exited with exit code 1 2021-01-17 17:06:21.902 EST  LOG: shutting down 2021-01-17 17:06:21.908 EST  LOG: database system is shut down done server stopped ==> Moving postgresql data from /usr/local/var/postgres to /usr/local/var/postgres.old... ==> Creating database... The files belonging to this database system will be owned by user "qrush". This user must also own the server process. The database cluster will be initialized with locale "C". The default text search configuration will be set to "english". Data page checksums are disabled. fixing permissions on existing directory /usr/local/var/postgres ... ok creating subdirectories ... ok selecting dynamic shared memory implementation ... posix selecting default max_connections ... 100 selecting default shared_buffers ... 128MB selecting default time zone ... America/New_York creating configuration files ... ok running bootstrap script ... ok performing post-bootstrap initialization ... ok syncing data to disk ... ok initdb: warning: enabling "trust" authentication for local connections You can change this by editing pg_hba.conf or using the option -A, or --auth-local and --auth-host, the next time you run initdb. Success. You can now start the database server using: /usr/local/opt/postgresql/bin/pg_ctl -D /usr/local/var/postgres -l logfile start ==> Migrating and upgrading data... Performing Consistency Checks ----------------------------- Checking cluster versions ok Checking database user is the install user ok Checking database connection settings ok Checking for prepared transactions ok Checking for reg* data types in user tables ok Checking for contrib/isn with bigint-passing mismatch ok Creating dump of global objects ok Creating dump of database schemas ok Checking for presence of required libraries ok Checking database user is the install user ok Checking for prepared transactions ok Checking for new cluster tablespace directories ok If pg_upgrade fails after this point, you must re-initdb the new cluster before continuing. Performing Upgrade ------------------ Analyzing all rows in the new cluster ok Freezing all rows in the new cluster ok Deleting files from new pg_xact ok Copying old pg_xact to new server ok Setting next transaction ID and epoch for new cluster ok Deleting files from new pg_multixact/offsets ok Copying old pg_multixact/offsets to new server ok Deleting files from new pg_multixact/members ok Copying old pg_multixact/members to new server ok Setting next multixact ID and offset for new cluster ok Resetting WAL archives ok Setting frozenxid and minmxid counters in new cluster ok Restoring global objects in the new cluster ok Restoring database schemas in the new cluster ok Copying user relation files ok Setting next OID for new cluster ok Sync data directory to disk ok Creating script to analyze new cluster ok Creating script to delete old cluster ok Upgrade Complete ---------------- Optimizer statistics are not transferred by pg_upgrade so, once you start the new server, consider running: ./analyze_new_cluster.sh Running this script will delete the old cluster's data files: ./delete_old_cluster.sh ==> Upgraded postgresql data from 12 to 13! ==> Your postgresql 12 data remains at /usr/local/var/postgres.old 💚 brew services start postgresql ==> Successfully started `postgresql` (label: homebrew.mxcl.postgresql)
I hope that helps someone in the future!
If your app works well once you've upgraded - your "old" Postgres 12 might take up a ton of space:
💚 du -ksh /usr/local/var/postgres.old 672M /usr/local/var/postgres.old
You can clean that up with:
💚 rm -rf /usr/local/var/postgres.old