pg_upgrade from Postgresql-15 to Postgresql-16 fails with postgis installed

I'm upgrading from Postgres 15 to 16 on Arch using the default documentation. When I reach the pg_upgrade section:

pg_upgrade -b /opt/pgsql-15/bin -B /usr/bin -d /var/lib/postgres/olddata -D /var/lib/postgres/data

Then I get a "failure" exit. When I check the pg_upgrade_output.d log file I found an error related to PostGIS path:

command: "/usr/bin/pg_dump" --host /var/lib/postgres --port 50432 --username postgres --schema-only --quote-all-identifiers --binary-upgrade --format=custom  --file="/var/lib/postgres/data/pg_upgrade_output.d/20231207T105131.842/dump/pg_upgrade_dump_16385.custom" 'dbname=linuxbox_db' >> "/var/lib/postgres/data/pg_upgrade_output.d/20231207T105131.842/log/pg_upgrade_dump_16385.log" 2>&1
pg_dump: error: query failed: ERROR:  could not access file "$libdir/postgis-3": No such file or directory

Is it something on my system or a bug in the pg_upgrade code?

Solution

The error was because I needed to rebuild the postgis library after installing v16 and before running the pg_upgrade.

If someone else ends up having trouble upgrading on Arch, here is a summary of the steps I followed:

check the modifications to postgis-old-upgrade for the latest postgresql version! (check AUR page)
Update all the db to current collation version. Get into psql from postgresql account and it will tell you the command to use or run the script https://gist.github.com/AlfredoRamos/63def9c77081a6dba7db38d3b0669cef
Stop postgresql from syscntl

sudo systemctl stop postgresql.service

Move the db data directory to olddata. https://wiki.archlinux.org/title/PostgreSQL#Upgrading_PostgreSQL

sudo mv /var/lib/postgres/data /var/lib/postgres/olddata

create new data directory and assign it to postgres user

sudo mkdir /var/lib/postgres/data /var/lib/postgres/tmp
sudo chown postgres:postgres /var/lib/postgres/data /var/lib/postgres/tmp

install new version of Postgres including postgresql-old-upgrade
get into postgres user and tmp directory

sudo -i -u postgres
[postgres]$ cd /var/lib/postgres/tmp

initialize new db as

[postgres]$ initdb -D /var/lib/postgres/data --locale=C.UTF-8 --encoding=UTF8

start systmctl service from my user

sudo systemctl start postgresql.service

update h3 from postgres account

pgxn install h3

rebuild libraries from pacman: gdal, postgis, postgis-old-upgrade, pgsql-ogr-fdw
stop systmctl service from my user

sudo systemctl stop postgresql.service

run pg_upgrade changing value to old version using the postgres account

[postgres]$ pg_upgrade -b /opt/pgsql-PG_VERSION/bin -B /usr/bin -d /var/lib/postgres/olddata -D /var/lib/postgres/data

check db is fine and remove tmp and olddata directories