pg_upgrade(1) PostgreSQL 18.6 Documentation pg_upgrade(1)
NAME
pg_upgrade - upgrade a PostgreSQL server instance
SYNOPSIS
pg_upgrade -b oldbindir [-B newbindir] -d oldconfigdir -D newconfigdir
[option...]
DESCRIPTION
pg_upgrade (formerly called pg_migrator) allows data stored in
PostgreSQL data files to be upgraded to a later PostgreSQL major
version without the data dump/restore typically required for major
version upgrades, e.g., from 12.14 to 13.10 or from 14.9 to 15.5. It is
not required for minor version upgrades, e.g., from 12.7 to 12.8 or
from 14.1 to 14.5.
Major PostgreSQL releases regularly add new features that often change
the layout of the system tables, but the internal data storage format
rarely changes. pg_upgrade uses this fact to perform rapid upgrades by
creating new system tables and simply reusing the old user data files.
If a future major release ever changes the data storage format in a way
that makes the old data format unreadable, pg_upgrade will not be
usable for such upgrades. (The community will attempt to avoid such
situations.)
pg_upgrade does its best to make sure the old and new clusters are
binary-compatible, e.g., by checking for compatible compile-time
settings, including 32/64-bit binaries. It is important that any
external modules are also binary compatible, though this cannot be
checked by pg_upgrade.
pg_upgrade supports upgrades from 9.2.X and later to the current major
release of PostgreSQL, including snapshot and beta releases.
Warning
Upgrading a cluster causes the destination to execute arbitrary
code of the source superusers' choice. Ensure that the source
superusers are trusted before upgrading.
OPTIONS
pg_upgrade accepts the following command-line arguments:
-b bindir
--old-bindir=bindir
the old PostgreSQL executable directory; environment variable
PGBINOLD
-B bindir
--new-bindir=bindir
the new PostgreSQL executable directory; default is the directory
where pg_upgrade resides; environment variable PGBINNEW
-c
--check
check clusters only, don't change any data
-d configdir
--old-datadir=configdir
the old database cluster configuration directory; environment
variable PGDATAOLD
-D configdir
--new-datadir=configdir
the new database cluster configuration directory; environment
variable PGDATANEW
-j njobs
--jobs=njobs
number of simultaneous connections and processes/threads to use
-k
--link
use hard links instead of copying files to the new cluster
-N
--no-sync
By default, pg_upgrade will wait for all files of the upgraded
cluster to be written safely to disk. This option causes pg_upgrade
to return without waiting, which is faster, but means that a
subsequent operating system crash can leave the data directory
corrupt. Generally, this option is useful for testing but should
not be used on a production installation.
-o options
--old-options options
options to be passed directly to the old postgres command; multiple
option invocations are appended
-O options
--new-options options
options to be passed directly to the new postgres command; multiple
option invocations are appended
-p port
--old-port=port
the old cluster port number; environment variable PGPORTOLD
-P port
--new-port=port
the new cluster port number; environment variable PGPORTNEW
-r
--retain
retain SQL and log files even after successful completion
-s dir
--socketdir=dir
directory to use for postmaster sockets during upgrade; default is
current working directory; environment variable PGSOCKETDIR
-U username
--username=username
cluster's install user name; environment variable PGUSER
-v
--verbose
enable verbose internal logging
-V
--version
display version information, then exit
--clone
Use efficient file cloning (also known as "reflinks" on some
systems) instead of copying files to the new cluster. This can
result in near-instantaneous copying of the data files, giving the
speed advantages of -k/--link while leaving the old cluster
untouched.
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.
--copy
Copy files to the new cluster. This is the default. (See also
--link, --clone, --copy-file-range, and --swap.)
--copy-file-range
Use the copy_file_range system call for efficient copying. On some
file systems this gives results similar to --clone, sharing
physical disk blocks, while on others it may still copy blocks, but
do so via an optimized path. At present, it is supported on Linux
and FreeBSD.
--no-statistics
Do not restore statistics from the old cluster into the new
cluster.
--set-char-signedness=option
Manually set the default char signedness of new clusters. Possible
values are signed and unsigned.
In the C language, the default signedness of the char type (when
not explicitly specified) varies across platforms. For example,
char defaults to signed char on x86 CPUs but to unsigned char on
ARM CPUs.
Starting from PostgreSQL 18, database clusters maintain their own
default char signedness setting, which can be used to ensure
consistent behavior across platforms with different default char
signedness. By default, pg_upgrade preserves the char signedness
setting when upgrading from an existing cluster. However, when
upgrading from PostgreSQL 17 or earlier, pg_upgrade adopts the char
signedness of the platform on which it was built.
This option allows you to explicitly set the default char
signedness for the new cluster, overriding any inherited values.
There are two specific scenarios where this option is relevant:
o If you are planning to migrate to a different platform after
the upgrade, you should not use this option. The default
behavior is right in this case. Instead, perform the upgrade on
the original platform without this flag, and then migrate the
cluster afterward. This is the recommended and safest approach.
o If you have already migrated the cluster to a platform with
different char signedness (for example, from an x86-based
system to an ARM-based system), you should use this option to
specify the signedness matching the original platform's default
char signedness. Additionally, it's essential not to modify any
data files between migrating data files and running pg_upgrade.
pg_upgrade should be the first operation that starts the
cluster on the new platform.
--swap
Move the data directories from the old cluster to the new cluster.
Then, replace the catalog files with those generated for the new
cluster. This mode can outperform --link, --clone, --copy, and
--copy-file-range, especially on clusters with many relations.
However, this mode creates many garbage files in the old cluster,
which can prolong the file synchronization step if
--sync-method=syncfs is used. Therefore, it is recommended to use
--sync-method=fsync with --swap.
Additionally, once the file transfer step begins, the old cluster
will be destructively modified and therefore will no longer be safe
to start. See Step 17 for details.
--sync-method=method
When set to fsync, which is the default, pg_upgrade will
recursively open and synchronize all files in the upgraded
cluster's data directory. The search for files will follow symbolic
links for the WAL directory and each configured tablespace.
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.
-?
--help
show help, then exit
USAGE
These are the steps to perform an upgrade with pg_upgrade:
Note
The steps to upgrade logical replication clusters are not covered
here; refer to Section 29.13 for details.
1. Optionally move the old cluster: If you are using a
version-specific installation directory, e.g., /opt/PostgreSQL/18,
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. 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/18 stop
or on Windows, using the proper service names:
NET STOP postgresql-12
NET STOP postgresql-18
Streaming replication and log-shipping standby servers must be
running during this shutdown so they receive all changes.
9. Prepare for standby server upgrades: If you are upgrading standby
servers using methods outlined in section Step 11, 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.
10. 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, cloned, or swapped 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. Swap mode may be the fastest if there are many relations,
but you will not be able to access your old cluster once the file
transfer step begins. Swap mode also requires that the old and new
cluster data directories be in the same file system.
Setting --jobs to 2 or higher allows pg_upgrade to process multiple
databases and tablespaces in parallel. A good starting point is the
number of CPU cores on the machine. This option can substantially
reduce the upgrade time for multi-database and multi-tablespace
servers.
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/18/data"
--old-bindir "C:/Program Files/PostgreSQL/12/bin"
--new-bindir "C:/Program Files/PostgreSQL/18/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, clone, copy-file-range, or swap mode, you
should use the option --link, --clone, --copy-file-range, or --swap
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 17 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.
11. 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/18 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_18_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.
12. 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.
13. Start the new server: The new server can now be safely started,
and then any rsync'ed standby servers.
14. 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.
15. Statistics: Unless the --no-statistics option is specified,
pg_upgrade will transfer most optimizer statistics from the old
cluster to the new cluster. This does not transfer all statistics,
such as those created explicitly with CREATE STATISTICS
(CREATE_STATISTICS(7)), custom statistics added by an extension, or
statistics collected by the cumulative statistics system.
Because not all statistics are transferred by pg_upgrade, you will
be instructed to run commands to regenerate that information at the
end of the upgrade. You might need to set connection parameters to
match your new cluster.
First, use vacuumdb --all --analyze-in-stages --missing-stats-only
to quickly generate minimal optimizer statistics for relations
without any. Then, use vacuumdb --all --analyze-only to ensure all
relations have updated cumulative statistics for triggering vacuum
and analyze. For both commands, the use of --jobs can speed it up.
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 ....
16. 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).
17. Reverting to old cluster: If, after running pg_upgrade, you wish
to revert to the old cluster, there are several options:
o If the --check option was used, the old cluster was unmodified;
it can be restarted.
o If neither --link nor --swap was used, the old cluster was
unmodified; it can be restarted.
o If the --link option was used, the data files might be shared
between the old and new cluster:
o If pg_upgrade aborted before linking started, the old
cluster was unmodified; it can be restarted.
o 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.
o 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.
o If the --swap option was used, the old cluster might be
destructively modified:
o If pg_upgrade aborts before reporting that the old cluster
is no longer safe to start, the old cluster was unmodified;
it can be restarted.
o If pg_upgrade has reported that the old cluster is no
longer safe to start, the old cluster was destructively
modified. The old cluster will need to be restored from
backup in this case.
ENVIRONMENT
Some environment variables can be used to provide defaults for
command-line options:
PGBINOLD
The old PostgreSQL executable directory; option -b/--old-bindir.
PGBINNEW
The new PostgreSQL executable directory; option -B/--new-bindir.
PGDATAOLD
The old database cluster configuration directory; option
-d/--old-datadir.
PGDATANEW
The new database cluster configuration directory; option
-D/--new-datadir.
PGPORTOLD
The old cluster port number; option -p/--old-port.
PGPORTNEW
The new cluster port number; option -P/--new-port.
PGSOCKETDIR
Directory to use for postmaster sockets during upgrade; option
-s/--socketdir.
PGUSER
Cluster's install user name; option -U/--username.
NOTES
pg_upgrade creates various working files, such as schema dumps, stored
within pg_upgrade_output.d in the directory of the new cluster. Each
run creates a new subdirectory named with a timestamp formatted as per
ISO 8601 (%Y%m%dT%H%M%S), where all its generated files are stored.
pg_upgrade_output.d and its contained files will be removed
automatically if pg_upgrade completes successfully; but in the event of
trouble, the files there may provide useful debugging information.
pg_upgrade launches short-lived postmasters in the old and new data
directories. Temporary Unix socket files for communication with these
postmasters are, by default, made in the current working directory. In
some situations the path name for the current directory might be too
long to be a valid socket name. In that case you can use the -s option
to put the socket files in some directory with a shorter path name. For
security, be sure that that directory is not readable or writable by
any other users. (This is not supported on Windows.)
All failure, rebuild, and reindex cases will be reported by pg_upgrade
if they affect your installation; post-upgrade scripts to rebuild
tables and indexes will be generated automatically. If you are trying
to automate the upgrade of many clusters, you should find that clusters
with identical database schemas require the same post-upgrade steps for
all cluster upgrades; this is because the post-upgrade steps are based
on the database schemas, and not user data.
For deployment testing, create a schema-only copy of the old cluster,
insert dummy data, and upgrade that.
pg_upgrade does not support upgrading of databases containing table
columns using these reg* OID-referencing system data types:
regcollation
regconfig
regdictionary
regnamespace
regoper
regoperator
regproc
regprocedure
(regclass, regrole, and regtype can be upgraded.)
If you want to use link mode and you do not want your old cluster to be
modified when the new cluster is started, consider using the clone
mode. If that is not available, make a copy of the old cluster and
upgrade that in link mode. To make a valid copy of the old cluster, use
rsync to create a dirty copy of the old cluster while the server is
running, then shut down the old server and run rsync --checksum again
to update the copy with any changes to make it consistent. (--checksum
is necessary because rsync only has file modification-time granularity
of one second.) You might want to exclude some files, e.g.,
postmaster.pid, as documented in Section 25.3.4. If your file system
supports file system snapshots or copy-on-write file copies, you can
use that to make a backup of the old cluster and tablespaces, though
the snapshot and copies must be created simultaneously or while the
database server is down.
SEE ALSO
initdb(1), pg_ctl(1), pg_dump(1), postgres(1)
PostgreSQL 18.6 2026 pg_upgrade(1)
postgresql 18.6_0 - Generated Wed Aug 26 14:40:19 CDT 2026