pg_upgrade

Optionally move the old cluster

If you are using a version-specific installation directory, e.g. /opt/PostgreSQL/9.1, you do not need to move the old cluster. The graphical installers all use version-specific installation directories.

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, build the new version

Build the new PostgreSQL source with configure flags that are compatible with the old cluster. pg_upgrade will check pg_controldata to make sure all settings are compatible before starting the upgrade.

Install the new PostgreSQL binaries

Install the new server's binaries and support files. pg_upgrade is included in a default installation.

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

Initialize the new PostgreSQL cluster

Initialize the new cluster using initdb. Again, use compatible initdb flags that match the old cluster. Many prebuilt installers do this step automatically. There is no need to start the new cluster.

Install custom shared object files

Install any custom shared object files (or DLLs) used by the old cluster into the new cluster, e.g. pgcrypto.so, whether they are from contrib or some other source. Do not install the schema definitions, e.g. pgcrypto.sql, because these will be upgraded from the old cluster. Also, any custom full text search files (dictionary, synonym, thesaurus, stop words) must also be copied to the new cluster.

Adjust authentication

pg_upgrade will connect to the old and new servers several times, so you might want to set authentication to peer in pg_hba.conf or use a ~/.pgpass file (see Section 32.15).

Stop both servers

Make sure both database servers are stopped using, on Unix, e.g.:

pg_ctl -D /opt/PostgreSQL/8.4 stop
pg_ctl -D /opt/PostgreSQL/9.0 stop

or on Windows, using the proper service names:

NET STOP postgresql-8.4
NET STOP postgresql-9.0

Streaming replication and log-shipping standby servers can remain running until a later step.

Verify standby servers

If you are upgrading Streaming Replication and Log-Shipping standby servers, verify that the old standby servers are caught up by running pg_controldata against the old primary and standby clusters. Verify that the "Latest checkpoint location" values match in all clusters. (There will be a mismatch if old standby servers were shut down before the old primary.)

Run pg_upgrade

Always run the pg_upgrade binary of the new server, not the old one. pg_upgrade requires the specification of the old and new cluster's data and executable (bin) directories. You can also specify user and port values, and whether you want the data linked instead of copied (the default).

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_xlog can be on different file systems.) See pg_upgrade --help for a full list of options.

The --jobs option allows multiple CPU cores to be used for copying/linking of files and to dump and reload 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 start a shell as the postgres user and set the proper path:

RUNAS /USER:postgres "CMD.EXE"
SET PATH=%PATH%;C:\Program Files\PostgreSQL\9.0\bin;

and then run pg_upgrade with quoted directories, e.g.:

pg_upgrade.exe
        --old-datadir "C:/Program Files/PostgreSQL/8.4/data"
        --new-datadir "C:/Program Files/PostgreSQL/9.0/data"
        --old-bindir "C:/Program Files/PostgreSQL/8.4/bin"
        --new-bindir "C:/Program Files/PostgreSQL/9.0/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 mode, you should use the --link option with --check to enable link-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 16 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.

Upgrade Streaming Replication and Log-Shipping standby servers

If you have Streaming Replication (see Section 26.2.5) or Log-Shipping (see Section 26.2) standby servers, follow these steps to upgrade them. You will not be running pg_upgrade on the standby servers, but rather rsync. Do not start any servers yet.

1. Install the new PostgreSQL binaries on standby servers

   Make sure the new binaries and support files are installed on all standby servers.

2. Make sure the new standby data directories do not exist

   Make sure the new standby data directories do not exist or are empty. If initdb was run, delete the standby server data directories.

3. Install custom shared object files

   Install the same custom shared object files on the new standbys that you installed in the new master cluster.

4. Stop standby servers

   If the standby servers are still running, stop them now using the above instructions.

5. Save configuration files

   Save any configuration files from the standbys you need to keep, e.g. postgresql.conf, recovery.conf, as these will be overwritten or removed in the next step.

6. Start and stop the new master cluster

   In the new master cluster, change wal_level to replica in the postgresql.conf file and then start and stop the cluster.

7. Run rsync

   From a directory that is above the old and new database cluster directories, run this for each slave:

   rsync --archive --delete --hard-links --size-only old_pgdata new_pgdata remote_dir
   

   where old_pgdata and new_pgdata are relative to the current directory, and remote_dir is above the old and new cluster directories on the standby server. The old and new relative cluster paths must match on the master and standby server. Consult the rsync manual page for details on specifying the remote directory, e.g. standbyhost:/opt/PostgreSQL/. rsync will be fast when pg_upgrade's --link mode is used because it will create hard links on the remote server rather than transferring user data. Unfortunately, rsync needlessly copies the files associated with temporary and unlogged tables.

   If you have tablespaces, you will need to run a similar rsync command for each tablespace directory. If you have relocated pg_xlog outside the data directories, rsync must be run on those directories too.

8. Configure streaming replication and log-shipping standby servers

   Configure the servers for log shipping. (You do not need to run pg_start_backup() and pg_stop_backup() or take a file system backup as the slaves are still synchronized with the master.)

Restore pg_hba.conf

If you modified pg_hba.conf, restore its original settings. It might also be necessary to adjust other configuration files in the new cluster to match the old cluster, e.g. postgresql.conf.

Start the new server

The new server can now be safely started, and then any rsync'ed standby servers.

Post-Upgrade processing

If any post-upgrade processing is required, pg_upgrade will issue warnings as it completes. It will also generate script files that must be run by the administrator. The script files will connect to each database that needs post-upgrade processing. Each script should be run using:

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

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

Caution: In general it is unsafe to access tables referenced in rebuild scripts until the rebuild scripts have run to completion; doing so could yield incorrect results or poor performance. Tables not referenced in rebuild scripts can be accessed immediately.

Statistics

Because optimizer statistics are not transferred by pg_upgrade, you will be instructed to run a command to regenerate that information at the end of the upgrade. You might need to set connection parameters to match your new cluster.

Delete old cluster

Once you are satisfied with the upgrade, you can delete the old cluster's data directories by running the script mentioned when pg_upgrade completes. (Automatic deletion is not possible if you have user-defined tablespaces inside the old data directory.) You can also delete the old installation directories (e.g. bin, share).

Reverting to old cluster

If, after running pg_upgrade, you wish to revert to the old cluster, there are several options:

• If you ran pg_upgrade with --check, no modifications were made to the old cluster and you can re-use it anytime.

• If you ran pg_upgrade with --link, the data files are shared between the old and new cluster. If you started the new cluster, the new server has written to those shared files and it is unsafe to use the old cluster.

• If you ran pg_upgrade without --link or did not start the new server, the old cluster was not modified except that, if linking started, a .old suffix was appended to $PGDATA/global/pg_control. To reuse the old cluster, possibly remove the .old suffix from $PGDATA/global/pg_control; you can then restart the old cluster.