pg\_upgrade

pg\_upgrade

1

Application

pg\_upgrade

upgrade a

PostgreSQL

server instance

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/reload typically required for major version
upgrades, e.g., from 9.5.8 to 9.6.4 or from 10.7 to 11.2. It is not
required for minor version upgrades, e.g., from 9.6.2 to 9.6.3 or from
10.1 to 10.2.

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.

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 processes or 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.

`-?`; `--help`

:   show help, then exit

Usage
=====

These are the steps to perform an upgrade with pg\_upgrade:

If you are using a version-specific installation directory, e.g.,
`/opt/PostgreSQL/MAJORVERSION`, 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.

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 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 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.

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.

Copy any custom full text search files (dictionary, synonym, thesaurus,
stop words) from the old to the new cluster.

`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 [???](#libpq-pgpass)).

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

    pg_ctl -D /opt/PostgreSQL/9.6 stop
    pg_ctl -D /opt/PostgreSQL/MAJORVERSION stop

or on Windows, using the proper service names:

    NET STOP postgresql-9.6
    NET STOP postgresql-MAJORVERSION

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

If you are upgrading standby servers using methods outlined in section
[step\_title](#pgupgrade-step-replicas), 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 or if the old standby
servers are still running.) Also, make sure `wal_level` is not set to
`minimal` in the `postgresql.conf` file on the new primary cluster.

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 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\MAJORVERSION\bin;

and then run pg\_upgrade with quoted directories, e.g.:

    pg_upgrade.exe
            --old-datadir "C:/Program Files/PostgreSQL/9.6/data"
            --new-datadir "C:/Program Files/PostgreSQL/MAJORVERSION/data"
            --old-bindir "C:/Program Files/PostgreSQL/9.6/bin"
            --new-bindir "C:/Program Files/PostgreSQL/MAJORVERSION/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\_title](#pgupgrade-step-revert) 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 used link mode and have Streaming Replication (see
[???](#streaming-replication)) or Log-Shipping (see
[???](#warm-standby)) 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.

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

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

Install the same extension shared object files on the new standbys that
you installed in the new primary cluster.

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

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.

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/9.5 \
          /opt/PostgreSQL/9.6 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_9.5_201510051 \
          /vol1/pg_tblsp/PG_9.6_201608131 standby.example.com:/vol1/pg_tblsp

If you have relocated `pg_wal` outside the data directories, rsync must
be run on those directories too.

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 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`.

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

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.

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.

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`).

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.

Notes
=====

pg\_upgrade creates various working files, such as schema dumps, stored
within `pg_upgrade_output.d` in the directory of the new cluster.

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 [???](#backup-lowlevel-base-backup).
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
========
