File cloning is only supported on some operating systems and file systems. If it is selected but not supported, the pg_upgrade run will error. At present, it is supported on Linux (kernel 4.5 or later) with Btrfs and XFS (on file systems created with reflink support), and on macOS with APFS.

On Linux, syncfs may be used instead to ask the operating system to synchronize the whole file systems that contain the upgraded cluster's data directory, its WAL files, and each tablespace. See recovery_init_sync_method for information about the caveats to be aware of when using syncfs.

This option has no effect when --no-sync is used.

If your installation directory is not version-specific, e.g., /usr/local/pgsql, it is necessary to move the current PostgreSQL install directory so it does not interfere with the new PostgreSQL installation. Once the current PostgreSQL server is shut down, it is safe to rename the PostgreSQL installation directory; assuming the old directory is /usr/local/pgsql, you can do:

mv /usr/local/pgsql /usr/local/pgsql.old

to rename the directory.

For source installs, if you wish to install the new server in a custom location, use the prefix variable:

make prefix=/usr/local/pgsql.new install

Before you start upgrading the publisher cluster, ensure that the subscription is temporarily disabled, by executing ALTER SUBSCRIPTION ... DISABLE. Re-enable the subscription after the upgrade.

There are some prerequisites for pg_upgrade to be able to upgrade the logical slots. If these are not met an error will be reported.

There are some prerequisites for pg_upgrade to be able to upgrade the subscriptions. If these are not met an error will be reported.

pg_ctl -D /opt/PostgreSQL/12 stop
pg_ctl -D /opt/PostgreSQL/17 stop

or on Windows, using the proper service names:

NET STOP postgresql-12
NET STOP postgresql-17

Streaming replication and log-shipping standby servers must be running during this shutdown so they receive all changes.

If you use link mode, the upgrade will be much faster (no file copying) and use less disk space, but you will not be able to access your old cluster once you start the new cluster after the upgrade. Link mode also requires that the old and new cluster data directories be in the same file system. (Tablespaces and pg_wal can be on different file systems.) Clone mode provides the same speed and disk space advantages but does not cause the old cluster to be unusable once the new cluster is started. Clone mode also requires that the old and new data directories be in the same file system. This mode is only available on certain operating systems and file systems.

The --jobs option allows multiple CPU cores to be used for copying/linking of files and to dump and restore database schemas in parallel; a good place to start is the maximum of the number of CPU cores and tablespaces. This option can dramatically reduce the time to upgrade a multi-database server running on a multiprocessor machine.

For Windows users, you must be logged into an administrative account, and then run pg_upgrade with quoted directories, e.g.:

pg_upgrade.exe


        --old-datadir "C:/Program Files/PostgreSQL/12/data"


        --new-datadir "C:/Program Files/PostgreSQL/17/data"


        --old-bindir "C:/Program Files/PostgreSQL/12/bin"


        --new-bindir "C:/Program Files/PostgreSQL/17/bin"

Once started, pg_upgrade will verify the two clusters are compatible and then do the upgrade. You can use pg_upgrade --check to perform only the checks, even if the old server is still running. pg_upgrade --check will also outline any manual adjustments you will need to make after the upgrade. If you are going to be using link or clone mode, you should use the option --link or --clone with --check to enable mode-specific checks. pg_upgrade requires write permission in the current directory.

Obviously, no one should be accessing the clusters during the upgrade. pg_upgrade defaults to running servers on port 50432 to avoid unintended client connections. You can use the same port number for both clusters when doing an upgrade because the old and new clusters will not be running at the same time. However, when checking an old running server, the old and new port numbers must be different.

If an error occurs while restoring the database schema, pg_upgrade will exit and you will have to revert to the old cluster as outlined in Step 19 below. To try pg_upgrade again, you will need to modify the old cluster so the pg_upgrade schema restore succeeds. If the problem is a contrib module, you might need to uninstall the contrib module from the old cluster and install it in the new cluster after the upgrade, assuming the module is not being used to store user data.

If you did not use link mode, do not have or do not want to use rsync, or want an easier solution, skip the instructions in this section and simply recreate the standby servers once pg_upgrade completes and the new primary is running.

rsync --archive --delete --hard-links --size-only --no-inc-recursive old_cluster new_cluster remote_dir

rsync --archive --delete --hard-links --size-only --no-inc-recursive /opt/PostgreSQL/12 \


      /opt/PostgreSQL/17 standby.example.com:/opt/PostgreSQL

rsync --archive --delete --hard-links --size-only --no-inc-recursive /vol1/pg_tblsp/PG_12_201909212 \


      /vol1/pg_tblsp/PG_17_202307071 standby.example.com:/vol1/pg_tblsp

psql --username=postgres --file=script.sql postgres

The scripts can be run in any order and can be deleted once they have been run.

Using vacuumdb --all --analyze-only can efficiently generate such statistics, and the use of --jobs can speed it up. Option --analyze-in-stages can be used to generate minimal statistics quickly. If vacuum_cost_delay is set to a non-zero value, this can be overridden to speed up statistics generation using PGOPTIONS, e.g., PGOPTIONS='-c vacuum_cost_delay=0' vacuumdb ....