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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>pg_upgrade</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="pgtesttiming.html" title="pg_test_timing" /><link rel="next" href="pgwaldump.html" title="pg_waldump" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center"><span class="application">pg_upgrade</span></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="pgtesttiming.html" title="pg_test_timing">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="reference-server.html" title="PostgreSQL Server Applications">Up</a></td><th width="60%" align="center">PostgreSQL Server Applications</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="pgwaldump.html" title="pg_waldump">Next</a></td></tr></table><hr /></div><div class="refentry" id="PGUPGRADE"><div class="titlepage"></div><a id="id-1.9.5.12.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle"><span class="application">pg_upgrade</span></span></h2><p>pg_upgrade — upgrade a <span class="productname">PostgreSQL</span> server instance</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p id="id-1.9.5.12.4.1"><code class="command">pg_upgrade</code> <code class="option">-b</code> <em class="replaceable"><code>oldbindir</code></em> [<code class="option">-B</code> <em class="replaceable"><code>newbindir</code></em>] <code class="option">-d</code> <em class="replaceable"><code>oldconfigdir</code></em> <code class="option">-D</code> <em class="replaceable"><code>newconfigdir</code></em> [<em class="replaceable"><code>option</code></em>...]</p></div></div><div class="refsect1" id="id-1.9.5.12.5"><h2>Description</h2><p>
<span class="application">pg_upgrade</span> (formerly called <span class="application">pg_migrator</span>) allows data
stored in <span class="productname">PostgreSQL</span> data files to be upgraded to a later <span class="productname">PostgreSQL</span>
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.
</p><p>
Major PostgreSQL releases regularly add new features that often
change the layout of the system tables, but the internal data storage
format rarely changes. <span class="application">pg_upgrade</span> 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, <span class="application">pg_upgrade</span> will not be usable
for such upgrades. (The community will attempt to avoid such
situations.)
</p><p>
<span class="application">pg_upgrade</span> 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 <span class="application">pg_upgrade</span>.
</p><p>
pg_upgrade supports upgrades from 9.2.X and later to the current
major release of <span class="productname">PostgreSQL</span>, including snapshot and beta releases.
</p></div><div class="refsect1" id="id-1.9.5.12.6"><h2>Options</h2><p>
<span class="application">pg_upgrade</span> accepts the following command-line arguments:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">-b</code> <em class="replaceable"><code>bindir</code></em><br /></span><span class="term"><code class="option">--old-bindir=</code><em class="replaceable"><code>bindir</code></em></span></dt><dd><p>the old PostgreSQL executable directory;
environment variable <code class="envar">PGBINOLD</code></p></dd><dt><span class="term"><code class="option">-B</code> <em class="replaceable"><code>bindir</code></em><br /></span><span class="term"><code class="option">--new-bindir=</code><em class="replaceable"><code>bindir</code></em></span></dt><dd><p>the new PostgreSQL executable directory;
default is the directory where <span class="application">pg_upgrade</span> resides;
environment variable <code class="envar">PGBINNEW</code></p></dd><dt><span class="term"><code class="option">-c</code><br /></span><span class="term"><code class="option">--check</code></span></dt><dd><p>check clusters only, don't change any data</p></dd><dt><span class="term"><code class="option">-d</code> <em class="replaceable"><code>configdir</code></em><br /></span><span class="term"><code class="option">--old-datadir=</code><em class="replaceable"><code>configdir</code></em></span></dt><dd><p>the old database cluster configuration directory; environment
variable <code class="envar">PGDATAOLD</code></p></dd><dt><span class="term"><code class="option">-D</code> <em class="replaceable"><code>configdir</code></em><br /></span><span class="term"><code class="option">--new-datadir=</code><em class="replaceable"><code>configdir</code></em></span></dt><dd><p>the new database cluster configuration directory; environment
variable <code class="envar">PGDATANEW</code></p></dd><dt><span class="term"><code class="option">-j <em class="replaceable"><code>njobs</code></em></code><br /></span><span class="term"><code class="option">--jobs=<em class="replaceable"><code>njobs</code></em></code></span></dt><dd><p>number of simultaneous processes or threads to use
</p></dd><dt><span class="term"><code class="option">-k</code><br /></span><span class="term"><code class="option">--link</code></span></dt><dd><p>use hard links instead of copying files to the new
cluster</p></dd><dt><span class="term"><code class="option">-N</code><br /></span><span class="term"><code class="option">--no-sync</code></span></dt><dd><p>
By default, <code class="command">pg_upgrade</code> will wait for all files
of the upgraded cluster to be written safely to disk. This option
causes <code class="command">pg_upgrade</code> 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.
</p></dd><dt><span class="term"><code class="option">-o</code> <em class="replaceable"><code>options</code></em><br /></span><span class="term"><code class="option">--old-options</code> <em class="replaceable"><code>options</code></em></span></dt><dd><p>options to be passed directly to the
old <code class="command">postgres</code> command; multiple
option invocations are appended</p></dd><dt><span class="term"><code class="option">-O</code> <em class="replaceable"><code>options</code></em><br /></span><span class="term"><code class="option">--new-options</code> <em class="replaceable"><code>options</code></em></span></dt><dd><p>options to be passed directly to the
new <code class="command">postgres</code> command; multiple
option invocations are appended</p></dd><dt><span class="term"><code class="option">-p</code> <em class="replaceable"><code>port</code></em><br /></span><span class="term"><code class="option">--old-port=</code><em class="replaceable"><code>port</code></em></span></dt><dd><p>the old cluster port number; environment
variable <code class="envar">PGPORTOLD</code></p></dd><dt><span class="term"><code class="option">-P</code> <em class="replaceable"><code>port</code></em><br /></span><span class="term"><code class="option">--new-port=</code><em class="replaceable"><code>port</code></em></span></dt><dd><p>the new cluster port number; environment
variable <code class="envar">PGPORTNEW</code></p></dd><dt><span class="term"><code class="option">-r</code><br /></span><span class="term"><code class="option">--retain</code></span></dt><dd><p>retain SQL and log files even after successful completion
</p></dd><dt><span class="term"><code class="option">-s</code> <em class="replaceable"><code>dir</code></em><br /></span><span class="term"><code class="option">--socketdir=</code><em class="replaceable"><code>dir</code></em></span></dt><dd><p>directory to use for postmaster sockets during upgrade;
default is current working directory; environment
variable <code class="envar">PGSOCKETDIR</code></p></dd><dt><span class="term"><code class="option">-U</code> <em class="replaceable"><code>username</code></em><br /></span><span class="term"><code class="option">--username=</code><em class="replaceable"><code>username</code></em></span></dt><dd><p>cluster's install user name; environment
variable <code class="envar">PGUSER</code></p></dd><dt><span class="term"><code class="option">-v</code><br /></span><span class="term"><code class="option">--verbose</code></span></dt><dd><p>enable verbose internal logging</p></dd><dt><span class="term"><code class="option">-V</code><br /></span><span class="term"><code class="option">--version</code></span></dt><dd><p>display version information, then exit</p></dd><dt><span class="term"><code class="option">--clone</code></span></dt><dd><p>
Use efficient file cloning (also known as <span class="quote">“<span class="quote">reflinks</span>”</span> 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 <code class="option">-k</code>/<code class="option">--link</code> while
leaving the old cluster untouched.
</p><p>
File cloning is only supported on some operating systems and file
systems. If it is selected but not supported, the
<span class="application">pg_upgrade</span> 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.
</p></dd><dt><span class="term"><code class="option">--copy</code></span></dt><dd><p>
Copy files to the new cluster. This is the default. (See also
<code class="option">--link</code> and <code class="option">--clone</code>.)
</p></dd><dt><span class="term"><code class="option">-?</code><br /></span><span class="term"><code class="option">--help</code></span></dt><dd><p>show help, then exit</p></dd></dl></div><p>
</p></div><div class="refsect1" id="id-1.9.5.12.7"><h2>Usage</h2><p>
These are the steps to perform an upgrade
with <span class="application">pg_upgrade</span>:
</p><div class="procedure"><ol class="procedure" type="1"><li class="step"><p class="title"><strong>Optionally move the old cluster</strong></p><p>
If you are using a version-specific installation directory, e.g.,
<code class="filename">/opt/PostgreSQL/16</code>, you do not need to move the old cluster. The
graphical installers all use version-specific installation directories.
</p><p>
If your installation directory is not version-specific, e.g.,
<code class="filename">/usr/local/pgsql</code>, it is necessary to move the current PostgreSQL install
directory so it does not interfere with the new <span class="productname">PostgreSQL</span> installation.
Once the current <span class="productname">PostgreSQL</span> server is shut down, it is safe to rename the
PostgreSQL installation directory; assuming the old directory is
<code class="filename">/usr/local/pgsql</code>, you can do:
</p><pre class="programlisting">
mv /usr/local/pgsql /usr/local/pgsql.old
</pre><p>
to rename the directory.
</p></li><li class="step"><p class="title"><strong>For source installs, build the new version</strong></p><p>
Build the new PostgreSQL source with <code class="command">configure</code> flags that are compatible
with the old cluster. <span class="application">pg_upgrade</span> will check <code class="command">pg_controldata</code> to make
sure all settings are compatible before starting the upgrade.
</p></li><li class="step"><p class="title"><strong>Install the new PostgreSQL binaries</strong></p><p>
Install the new server's binaries and support
files. <span class="application">pg_upgrade</span> is included in a default installation.
</p><p>
For source installs, if you wish to install the new server in a custom
location, use the <code class="literal">prefix</code> variable:
</p><pre class="programlisting">
make prefix=/usr/local/pgsql.new install
</pre></li><li class="step"><p class="title"><strong>Initialize the new PostgreSQL cluster</strong></p><p>
Initialize the new cluster using <code class="command">initdb</code>.
Again, use compatible <code class="command">initdb</code>
flags that match the old cluster. Many
prebuilt installers do this step automatically. There is no need to
start the new cluster.
</p></li><li class="step"><p class="title"><strong>Install extension shared object files</strong></p><p>
Many extensions and custom modules, whether from
<code class="filename">contrib</code> or another source, use shared object
files (or DLLs), e.g., <code class="filename">pgcrypto.so</code>. 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., <code class="command">CREATE
EXTENSION pgcrypto</code>, because these will be duplicated from
the old cluster. If extension updates are available,
<span class="application">pg_upgrade</span> will report this and create
a script that can be run later to update them.
</p></li><li class="step"><p class="title"><strong>Copy custom full-text search files</strong></p><p>
Copy any custom full text search files (dictionary, synonym,
thesaurus, stop words) from the old to the new cluster.
</p></li><li class="step"><p class="title"><strong>Adjust authentication</strong></p><p>
<code class="command">pg_upgrade</code> will connect to the old and new servers several
times, so you might want to set authentication to <code class="literal">peer</code>
in <code class="filename">pg_hba.conf</code> or use a <code class="filename">~/.pgpass</code> file
(see <a class="xref" href="libpq-pgpass.html" title="34.16. The Password File">Section 34.16</a>).
</p></li><li class="step"><p class="title"><strong>Stop both servers</strong></p><p>
Make sure both database servers are stopped using, on Unix, e.g.:
</p><pre class="programlisting">
pg_ctl -D /opt/PostgreSQL/12 stop
pg_ctl -D /opt/PostgreSQL/16 stop
</pre><p>
or on Windows, using the proper service names:
</p><pre class="programlisting">
NET STOP postgresql-12
NET STOP postgresql-16
</pre><p>
</p><p>
Streaming replication and log-shipping standby servers must be
running during this shutdown so they receive all changes.
</p></li><li class="step"><p class="title"><strong>Prepare for standby server upgrades</strong></p><p>
If you are upgrading standby servers using methods outlined in section <a class="xref" href="pgupgrade.html#PGUPGRADE-STEP-REPLICAS" title="Upgrade streaming replication and log-shipping standby servers">Step 11</a>, verify that the old standby
servers are caught up by running <span class="application">pg_controldata</span>
against the old primary and standby clusters. Verify that the
<span class="quote">“<span class="quote">Latest checkpoint location</span>”</span> values match in all clusters.
Also, make sure <code class="varname">wal_level</code> is not set to
<code class="literal">minimal</code> in the <code class="filename">postgresql.conf</code> file on the
new primary cluster.
</p></li><li class="step"><p class="title"><strong>Run <span class="application">pg_upgrade</span></strong></p><p>
Always run the <span class="application">pg_upgrade</span> binary of the new server, not the old one.
<span class="application">pg_upgrade</span> requires the specification of the old and new cluster's
data and executable (<code class="filename">bin</code>) 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.
</p><p>
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 <code class="filename">pg_wal</code> 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.
</p><p>
The <code class="option">--jobs</code> 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.
</p><p>
For Windows users, you must be logged into an administrative account, and
then start a shell as the <code class="literal">postgres</code> user and set the proper path:
</p><pre class="programlisting">
RUNAS /USER:postgres "CMD.EXE"
SET PATH=%PATH%;C:\Program Files\PostgreSQL\16\bin;
</pre><p>
and then run <span class="application">pg_upgrade</span> with quoted directories, e.g.:
</p><pre class="programlisting">
pg_upgrade.exe
--old-datadir "C:/Program Files/PostgreSQL/12/data"
--new-datadir "C:/Program Files/PostgreSQL/16/data"
--old-bindir "C:/Program Files/PostgreSQL/12/bin"
--new-bindir "C:/Program Files/PostgreSQL/16/bin"
</pre><p>
Once started, <code class="command">pg_upgrade</code> will verify the two clusters are compatible
and then do the upgrade. You can use <code class="command">pg_upgrade --check</code>
to perform only the checks, even if the old server is still
running. <code class="command">pg_upgrade --check</code> 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
<code class="option">--link</code> or <code class="option">--clone</code> with
<code class="option">--check</code> to enable mode-specific checks.
<code class="command">pg_upgrade</code> requires write permission in the current directory.
</p><p>
Obviously, no one should be accessing the clusters during the
upgrade. <span class="application">pg_upgrade</span> 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.
</p><p>
If an error occurs while restoring the database schema, <code class="command">pg_upgrade</code> will
exit and you will have to revert to the old cluster as outlined in <a class="xref" href="pgupgrade.html#PGUPGRADE-STEP-REVERT" title="Reverting to old cluster">Step 17</a>
below. To try <code class="command">pg_upgrade</code> again, you will need to modify the old
cluster so the pg_upgrade schema restore succeeds. If the problem is a
<code class="filename">contrib</code> module, you might need to uninstall the <code class="filename">contrib</code> 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.
</p></li><li class="step" id="PGUPGRADE-STEP-REPLICAS"><p class="title"><strong>Upgrade streaming replication and log-shipping standby servers</strong></p><p>
If you used link mode and have Streaming Replication (see <a class="xref" href="warm-standby.html#STREAMING-REPLICATION" title="27.2.5. Streaming Replication">Section 27.2.5</a>) or Log-Shipping (see <a class="xref" href="warm-standby.html" title="27.2. Log-Shipping Standby Servers">Section 27.2</a>) standby servers, you can follow these steps to
quickly upgrade them. You will not be running <span class="application">pg_upgrade</span> on
the standby servers, but rather <span class="application">rsync</span> on the primary.
Do not start any servers yet.
</p><p>
If you did <span class="emphasis"><em>not</em></span> use link mode, do not have or do not
want to use <span class="application">rsync</span>, or want an easier solution, skip
the instructions in this section and simply recreate the standby
servers once <span class="application">pg_upgrade</span> completes and the new primary
is running.
</p><div class="procedure"><ol class="procedure" type="1"><li class="step"><p class="title"><strong>Install the new PostgreSQL binaries on standby servers</strong></p><p>
Make sure the new binaries and support files are installed on all
standby servers.
</p></li><li class="step"><p class="title"><strong>Make sure the new standby data directories do <span class="emphasis"><em>not</em></span> exist</strong></p><p>
Make sure the new standby data directories do <span class="emphasis"><em>not</em></span>
exist or are empty. If <span class="application">initdb</span> was run, delete
the standby servers' new data directories.
</p></li><li class="step"><p class="title"><strong>Install extension shared object files</strong></p><p>
Install the same extension shared object files on the new standbys
that you installed in the new primary cluster.
</p></li><li class="step"><p class="title"><strong>Stop standby servers</strong></p><p>
If the standby servers are still running, stop them now using the
above instructions.
</p></li><li class="step"><p class="title"><strong>Save configuration files</strong></p><p>
Save any configuration files from the old standbys' configuration
directories you need to keep, e.g., <code class="filename">postgresql.conf</code>
(and any files included by it), <code class="filename">postgresql.auto.conf</code>,
<code class="literal">pg_hba.conf</code>, because these will be overwritten
or removed in the next step.
</p></li><li class="step"><p class="title"><strong>Run <span class="application">rsync</span></strong></p><p>
When using link mode, standby servers can be quickly upgraded using
<span class="application">rsync</span>. To accomplish this, from a directory on
the primary server that is above the old and new database cluster
directories, run this on the <span class="emphasis"><em>primary</em></span> for each standby
server:
</p><pre class="programlisting">
rsync --archive --delete --hard-links --size-only --no-inc-recursive old_cluster new_cluster remote_dir
</pre><p>
where <code class="option">old_cluster</code> and <code class="option">new_cluster</code> are relative
to the current directory on the primary, and <code class="option">remote_dir</code>
is <span class="emphasis"><em>above</em></span> 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
<span class="application">rsync</span> manual page for details on specifying the
remote directory, e.g.,
</p><pre class="programlisting">
rsync --archive --delete --hard-links --size-only --no-inc-recursive /opt/PostgreSQL/12 \
/opt/PostgreSQL/16 standby.example.com:/opt/PostgreSQL
</pre><p>
You can verify what the command will do using
<span class="application">rsync</span>'s <code class="option">--dry-run</code> option. While
<span class="application">rsync</span> must be run on the primary for at least one
standby, it is possible to run <span class="application">rsync</span> on an upgraded
standby to upgrade other standbys, as long as the upgraded standby
has not been started.
</p><p>
What this does is to record the links created by
<span class="application">pg_upgrade</span>'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,
<span class="application">rsync</span> needlessly copies files associated with
temporary and unlogged tables because these files don't normally
exist on standby servers.
</p><p>
If you have tablespaces, you will need to run a similar
<span class="application">rsync</span> command for each tablespace directory, e.g.:
</p><pre class="programlisting">
rsync --archive --delete --hard-links --size-only --no-inc-recursive /vol1/pg_tblsp/PG_12_201909212 \
/vol1/pg_tblsp/PG_16_202307071 standby.example.com:/vol1/pg_tblsp
</pre><p>
If you have relocated <code class="filename">pg_wal</code> outside the data
directories, <span class="application">rsync</span> must be run on those directories
too.
</p></li><li class="step"><p class="title"><strong>Configure streaming replication and log-shipping standby servers</strong></p><p>
Configure the servers for log shipping. (You do not need to run
<code class="function">pg_backup_start()</code> and <code class="function">pg_backup_stop()</code>
or take a file system backup as the standbys are still synchronized
with the primary.) Replication slots are not copied and must
be recreated.
</p></li></ol></div></li><li class="step"><p class="title"><strong>Restore <code class="filename">pg_hba.conf</code></strong></p><p>
If you modified <code class="filename">pg_hba.conf</code>, 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., <code class="filename">postgresql.conf</code>
(and any files included by it), <code class="filename">postgresql.auto.conf</code>.
</p></li><li class="step"><p class="title"><strong>Start the new server</strong></p><p>
The new server can now be safely started, and then any
<span class="application">rsync</span>'ed standby servers.
</p></li><li class="step"><p class="title"><strong>Post-upgrade processing</strong></p><p>
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:
</p><pre class="programlisting">
psql --username=postgres --file=script.sql postgres
</pre><p>
The scripts can be run in any order and can be deleted once they have
been run.
</p><div class="caution"><h3 class="title">Caution</h3><p>
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.
</p></div></li><li class="step"><p class="title"><strong>Statistics</strong></p><p>
Because optimizer statistics are not transferred by <code class="command">pg_upgrade</code>, 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.
</p></li><li class="step"><p class="title"><strong>Delete old cluster</strong></p><p>
Once you are satisfied with the upgrade, you can delete the old
cluster's data directories by running the script mentioned when
<code class="command">pg_upgrade</code> 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., <code class="filename">bin</code>, <code class="filename">share</code>).
</p></li><li class="step" id="PGUPGRADE-STEP-REVERT"><p class="title"><strong>Reverting to old cluster</strong></p><p>
If, after running <code class="command">pg_upgrade</code>, you wish to revert to the old cluster,
there are several options:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
If the <code class="option">--check</code> option was used, the old cluster
was unmodified; it can be restarted.
</p></li><li class="listitem"><p>
If the <code class="option">--link</code> option was <span class="emphasis"><em>not</em></span>
used, the old cluster was unmodified; it can be restarted.
</p></li><li class="listitem"><p>
If the <code class="option">--link</code> option was used, the data
files might be shared between the old and new cluster:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>
If <code class="command">pg_upgrade</code> aborted before linking started,
the old cluster was unmodified; it can be restarted.
</p></li><li class="listitem"><p>
If you did <span class="emphasis"><em>not</em></span> start the new cluster, the old
cluster was unmodified except that, when linking started, a
<code class="literal">.old</code> suffix was appended to
<code class="filename">$PGDATA/global/pg_control</code>. To reuse the old
cluster, remove the <code class="filename">.old</code> suffix from
<code class="filename">$PGDATA/global/pg_control</code>; you can then restart
the old cluster.
</p></li><li class="listitem"><p>
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.
</p></li></ul></div></li></ul></div></li></ol></div></div><div class="refsect1" id="id-1.9.5.12.8"><h2>Notes</h2><p>
<span class="application">pg_upgrade</span> creates various working files, such
as schema dumps, stored within <code class="filename">pg_upgrade_output.d</code> in
the directory of the new cluster. Each run creates a new subdirectory named
with a timestamp formatted as per ISO 8601
(<code class="literal">%Y%m%dT%H%M%S</code>), where all its generated files are
stored.
<code class="filename">pg_upgrade_output.d</code> and its contained files will be
removed automatically if <span class="application">pg_upgrade</span> completes
successfully; but in the event of trouble, the files there may provide
useful debugging information.
</p><p>
<span class="application">pg_upgrade</span> 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 <code class="option">-s</code> 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.)
</p><p>
All failure, rebuild, and reindex cases will be reported by
<span class="application">pg_upgrade</span> 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.
</p><p>
For deployment testing, create a schema-only copy of the old cluster,
insert dummy data, and upgrade that.
</p><p>
<span class="application">pg_upgrade</span> does not support upgrading of databases
containing table columns using these <code class="type">reg*</code> OID-referencing system data types:
</p><table border="0" summary="Simple list" class="simplelist"><tr><td><code class="type">regcollation</code></td></tr><tr><td><code class="type">regconfig</code></td></tr><tr><td><code class="type">regdictionary</code></td></tr><tr><td><code class="type">regnamespace</code></td></tr><tr><td><code class="type">regoper</code></td></tr><tr><td><code class="type">regoperator</code></td></tr><tr><td><code class="type">regproc</code></td></tr><tr><td><code class="type">regprocedure</code></td></tr></table><p>
(<code class="type">regclass</code>, <code class="type">regrole</code>, and <code class="type">regtype</code> can be upgraded.)
</p><p>
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 <code class="command">rsync</code> to create a dirty
copy of the old cluster while the server is running, then shut down
the old server and run <code class="command">rsync --checksum</code> again to update the
copy with any changes to make it consistent. (<code class="option">--checksum</code>
is necessary because <code class="command">rsync</code> only has file modification-time
granularity of one second.) You might want to exclude some
files, e.g., <code class="filename">postmaster.pid</code>, as documented in <a class="xref" href="continuous-archiving.html#BACKUP-LOWLEVEL-BASE-BACKUP" title="26.3.3. Making a Base Backup Using the Low Level API">Section 26.3.3</a>. 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.
</p></div><div class="refsect1" id="id-1.9.5.12.9"><h2>See Also</h2><span class="simplelist"><a class="xref" href="app-initdb.html" title="initdb"><span class="refentrytitle"><span class="application">initdb</span></span></a>, <a class="xref" href="app-pg-ctl.html" title="pg_ctl"><span class="refentrytitle"><span class="application">pg_ctl</span></span></a>, <a class="xref" href="app-pgdump.html" title="pg_dump"><span class="refentrytitle"><span class="application">pg_dump</span></span></a>, <a class="xref" href="app-postgres.html" title="postgres"><span class="refentrytitle"><span class="application">postgres</span></span></a></span></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="pgtesttiming.html" title="pg_test_timing">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="reference-server.html" title="PostgreSQL Server Applications">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="pgwaldump.html" title="pg_waldump">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span class="application">pg_test_timing</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="40%" align="right" valign="top"> <span class="application">pg_waldump</span></td></tr></table></div></body></html>