pg_upgrade (original) (raw)

1. Optionally move the old cluster
   If you are using a version-specific installation directory, e.g., /opt/PostgreSQL/17, 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.
2. 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.
3. 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
4. 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.
5. Install extension shared object files
   Many extensions and custom modules, whether from contrib or another source, use shared object files (or DLLs), e.g., pgcrypto.so. If the old cluster used these, shared object files matching the new server binary must be installed in the new cluster, usually via operating system commands. Do not load the schema definitions, e.g., CREATE EXTENSION pgcrypto, because these will be duplicated from the old cluster. If extension updates are available, pg_upgrade will report this and create a script that can be run later to update them.
6. Copy custom full-text search files
   Copy any custom full text search files (dictionary, synonym, thesaurus, stop words) from the old to the new cluster.
7. 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 32.16).
8. Prepare for publisher upgrades
   pg_upgrade attempts to migrate logical slots. This helps avoid the need for manually defining the same logical slots on the new publisher. Migration of logical slots is only supported when the old cluster is version 17.0 or later. Logical slots on clusters before version 17.0 will silently be ignored.
   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.
   • The new cluster must have wal_level as logical.
   • The new cluster must have max_replication_slots configured to a value greater than or equal to the number of slots present in the old cluster.
   • The output plugins referenced by the slots on the old cluster must be installed in the new PostgreSQL executable directory.
   • The old cluster has replicated all the transactions and logical decoding messages to subscribers.
   • All slots on the old cluster must be usable, i.e., there are no slots whose pg_replication_slots.conflicting is not true.
   • The new cluster must not have permanent logical slots, i.e., there must be no slots where pg_replication_slots.temporary is false.
9. Prepare for subscriber upgrades
   Setup the subscriber configurations in the new subscriber. pg_upgrade attempts to migrate subscription dependencies which includes the subscription's table information present in pg_subscription_rel system catalog and also the subscription's replication origin. This allows logical replication on the new subscriber to continue from where the old subscriber was up to. Migration of subscription dependencies is only supported when the old cluster is version 17.0 or later. Subscription dependencies on clusters before version 17.0 will silently be ignored.
   There are some prerequisites for pg_upgrade to be able to upgrade the subscriptions. If these are not met an error will be reported.
   • All the subscription tables in the old subscriber should be in state i (initialize) or r (ready). This can be verified by checking pg_subscription_rel.srsubstate.
   • The replication origin entry corresponding to each of the subscriptions should exist in the old cluster. This can be found by checking pg_subscription and pg_replication_origin system tables.
   • The new cluster must have max_replication_slots configured to a value greater than or equal to the number of subscriptions present in the old cluster.
10. Stop both servers
    Make sure both database servers are stopped using, on Unix, e.g.:
    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.
11. Prepare for standby server upgrades
    If you are upgrading standby servers using methods outlined in section Step 13, 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. Also, make sure wal_level is not set to minimal in the postgresql.conf file on the new primary cluster.
12. 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 files linked or cloned instead of the default copy behavior.
    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. 13. Upgrade streaming replication and log-shipping standby servers
If you used link mode and have Streaming Replication (see Section 26.2.5) or Log-Shipping (see Section 26.2) standby servers, you can follow these steps to quickly upgrade them. You will not be running pg_upgrade on the standby servers, but rather rsync on the primary. Do not start any servers yet.
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.

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 servers' new data directories.
3. Install extension shared object files
   Install the same extension shared object files on the new standbys that you installed in the new primary 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 old standbys' configuration directories you need to keep, e.g., postgresql.conf (and any files included by it), postgresql.auto.conf, pg_hba.conf, because these will be overwritten or removed in the next step.
6. Run rsync
   When using link mode, standby servers can be quickly upgraded using rsync. To accomplish this, from a directory on the primary server that is above the old and new database cluster directories, run this on the primary for each standby server:
   rsync --archive --delete --hard-links --size-only --no-inc-recursive old_cluster new_cluster remote_dir
   where old_cluster and new_cluster are relative to the current directory on the primary, and remote_dir is above the old and new cluster directories on the standby. The directory structure under the specified directories on the primary and standbys must match. Consult the rsync manual page for details on specifying the remote directory, e.g.,
   rsync --archive --delete --hard-links --size-only --no-inc-recursive /opt/PostgreSQL/12 \
   /opt/PostgreSQL/17 standby.example.com:/opt/PostgreSQL
   You can verify what the command will do using rsync's --dry-run option. While rsync must be run on the primary for at least one standby, it is possible to run rsync on an upgraded standby to upgrade other standbys, as long as the upgraded standby has not been started.
   What this does is to record the links created by pg_upgrade's link mode that connect files in the old and new clusters on the primary server. It then finds matching files in the standby's old cluster and creates links for them in the standby's new cluster. Files that were not linked on the primary are copied from the primary to the standby. (They are usually small.) This provides rapid standby upgrades. Unfortunately, rsync needlessly copies files associated with temporary and unlogged tables because these files don't normally exist on standby servers.
   If you have tablespaces, you will need to run a similar rsync command for each tablespace directory, e.g.:
   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
   If you have relocated pg_wal outside the data directories, rsync must be run on those directories too.
7. Configure streaming replication and log-shipping standby servers
   Configure the servers for log shipping. (You do not need to run pg_backup_start() and pg_backup_stop() or take a file system backup as the standbys are still synchronized with the primary.) If the old primary is prior to version 17.0, then no slots on the primary are copied to the new standby, so all the slots on the old standby must be recreated manually. If the old primary is version 17.0 or later, then only logical slots on the primary are copied to the new standby, but other slots on the old standby are not copied, so must be recreated manually.
8. 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 (and any files included by it), postgresql.auto.conf.
9. Start the new server
   The new server can now be safely started, and then any rsync'ed standby servers.
10. 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. 17. 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.
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 .... 18. 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). 19. Reverting to old cluster
If, after running pg_upgrade, you wish to revert to the old cluster, there are several options:

• If the --check option was used, the old cluster was unmodified; it can be restarted.
• If the --link option was not used, the old cluster was unmodified; it can be restarted.
• If the --link option was used, the data files might be shared between the old and new cluster:
  * If pg_upgrade aborted before linking started, the old cluster was unmodified; it can be restarted.
  * If you did not start the new cluster, the old cluster was unmodified except that, when linking started, a .old suffix was appended to $PGDATA/global/pg_control. To reuse the old cluster, remove the .old suffix from $PGDATA/global/pg_control; you can then restart the old cluster.
  * If you did start the new cluster, it has written to shared files and it is unsafe to use the old cluster. The old cluster will need to be restored from backup in this case.