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$PostgreSQL: pgsql/doc/src/sgml/ref/pg_dump.sgml,v 1.68 2003/12/01 22:07:58 momjian Exp $
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PostgreSQL documentation
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<refentry id="APP-PGDUMP">
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<refentrytitle>pg_dump</refentrytitle>
<manvolnum>1</manvolnum>
<refmiscinfo>Application</refmiscinfo>
</refmeta>
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<refname>pg_dump</refname>
extract a <productname>PostgreSQL</productname> database into a script file or other archive file
</refpurpose>
</refnamediv>
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<indexterm zone="app-pgdump">
<primary>pg_dump</primary>
</indexterm>
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<cmdsynopsis>
<command>pg_dump</command>
<arg rep="repeat"><replaceable>option</replaceable></arg>
<arg><replaceable>dbname</replaceable></arg>
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</cmdsynopsis>
</refsynopsisdiv>
<refsect1 id="pg-dump-description">
<title>
Description
</title>
<para>
<application>pg_dump</application> is a utility for backing up a
<productname>PostgreSQL</productname> database. It makes consistent
backups even if the database is being used concurrently.
<application>pg_dump</application> does not block other users
accessing the database (readers or writers).
Dumps can be output in script or archive file formats. The script
files are in plain-text format and contain the SQL commands required
to reconstruct the database to the state it was in at the time it was
saved. To restore these scripts, use <xref linkend="app-psql">. They
can be used to reconstruct the database even on other machines and
other architectures, with some modifications even on other SQL
database products.
</para>
<para>
The alternative archive file formats that are meant to be used with
<xref linkend="app-pgrestore"> to rebuild the database, and they also
allow <application>pg_restore</application> to be selective about
what is restored, or even to reorder the items prior to being
restored. The archive files are also designed to be portable across
architectures.
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</para>
<para>
When used with one of the archive file formats and combined with
<application>pg_restore</application>,
<application>pg_dump</application> provides a flexible archival and
transfer mechanism. <application>pg_dump</application> can be used to
backup an entire database, then <application>pg_restore</application>
can be used to examine the archive and/or select which parts of the
database are to be restored. The most flexible output file format is
the <quote>custom</quote> format (<option>-Fc</option>). It allows
for selection and reordering of all archived items, and is compressed
by default. The <application>tar</application> format
(<option>-Ft</option>) is not compressed and it is not possible to
reorder data when loading, but it is otherwise quite flexible;
moreover, it can be manipulated with other tools such as
<command>tar</command>.
</para>
<para>
While running <application>pg_dump</application>, one should examine the
output for any warnings (printed on standard error), especially in
light of the limitations listed below.
</para>
</refsect1>
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<refsect1 id="pg-dump-options">
<title>Options</title>
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<para>
The following command-line options are used to control the output format.
<variablelist>
<varlistentry>
<term><replaceable class="parameter">dbname</replaceable></term>
<listitem>
<para>
Specifies the name of the database to be dumped. If this is
not specified, the environment variable
<envar>PGDATABASE</envar> is used. If that is not set, the
user name specified for the connection is used.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-a</></term>
<term><option>--data-only</></term>
<listitem>
<para>
Dump only the data, not the schema (data definitions).
This option is only meaningful for the plain-text format. For
the other formats, you may specify the option when you
call <command>pg_restore</command>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-b</></term>
<term><option>--blobs</></term>
<listitem>
<para>
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Include large objects in dump.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-c</option></term>
<term><option>--clean</option></term>
<listitem>
<para>
Output commands to clean (drop)
database objects prior to (the commands for) creating them.
</para>
<para>
This option is only meaningful for the plain-text format. For
the other formats, you may specify the option when you
call <command>pg_restore</command>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-C</></term>
<term><option>--create</></term>
<listitem>
<para>
Begin the output with a command to create the
database itself and reconnect to the created database. (With a
script of this form, it doesn't matter which database you connect
to before running the script.)
</para>
<para>
This option is only meaningful for the plain-text format. For
the other formats, you may specify the option when you
call <command>pg_restore</command>.
</para>
</listitem>
</varlistentry>
<term><option>-d</option></term>
<term><option>--inserts</option></term>
<listitem>
<para>
Dump data as <command>INSERT</command> commands (rather
than <command>COPY</command>). This will make restoration very
slow, but it makes the archives more portable to other SQL database
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-D</option></term>
<term><option>--column-inserts</option></term>
<term><option>--attribute-inserts</option></term>
<listitem>
<para>
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Dump data as <command>INSERT</command> commands with explicit
column names (<literal>INSERT INTO
<replaceable>table</replaceable>
(<replaceable>column</replaceable>, ...) VALUES
...</literal>). This will make restoration very slow,
but it is necessary if you desire to rearrange the column ordering.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-f <replaceable class="parameter">file</replaceable></option></term>
<term><option>--file=<replaceable class="parameter">file</replaceable></option></term>
<listitem>
<para>
Send output to the specified file. If this is omitted, the
standard output is used.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-F <replaceable class="parameter">format</replaceable></option></term>
<term><option>--format=<replaceable class="parameter">format</replaceable></option></term>
<listitem>
<para>
Selects the format of the output.
<replaceable>format</replaceable> can be one of the following:
<variablelist>
<varlistentry>
<term><literal>p</></term>
<listitem>
<para>
Output a plain-text <acronym>SQL</acronym> script file (default)
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>t</></term>
<listitem>
<para>
Output a <command>tar</command> archive suitable for input into
<application>pg_restore</application>. Using this archive format
allows reordering and/or exclusion of schema elements
at the time the database is restored. It is also possible to limit
which data is reloaded at restore time.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>c</></term>
<listitem>
<para>
<application>pg_restore</application>. This is the most flexible
format in that it allows reordering of data load as well
as schema elements. This format is also compressed by default.
</para>
</listitem>
</varlistentry>
</variablelist>
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</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-i</></term>
<term><option>--ignore-version</></term>
<listitem>
<para>
Ignore version mismatch between
<application>pg_dump</application> and the database server.
</para>
<para>
<application>pg_dump</application> can handle databases from
previous releases of <productname>PostgreSQL</>, but very old
versions are not supported anymore (currently prior to 7.0).
Use this option if you need to override the version check (and
if <application>pg_dump</application> then fails, don't say
you weren't warned).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-n <replaceable class="parameter">namespace</replaceable></option></term>
<term><option>--schema=<replaceable class="parameter">schema</replaceable></option></term>
<listitem>
<para>
Dump the contents of <replaceable class="parameter">schema</>
only. If this option is not specified, all non-system schemas
in the target database will be dumped.
</para>
<note>
<para>
In this mode, <application>pg_dump</application> makes no
attempt to dump any other database objects that objects in the
selected schema may depend upon. Therefore, there is no
guarantee that the results of a single-schema dump can be
successfully restored by themselves into a clean database.
</para>
</note>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-o</></term>
<term><option>--oids</></term>
<listitem>
<para>
Dump object identifiers (<acronym>OID</acronym>s) for every
table. Use this option if your application references the <acronym>OID</>
columns in some way (e.g., in a foreign key constraint).
Otherwise, this option should not be used.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-O</></term>
<term><option>--no-owner</option></term>
<listitem>
<para>
Do not output commands to set
ownership of objects to match the original database.
By default, <application>pg_dump</application> issues
<command>SET SESSION AUTHORIZATION</command>
statements to set ownership of created schema elements.
These statements
will fail when the script is run unless it is started by a superuser
(or the same user that owns all of the objects in the script).
To make a script that can be restored by any user, but will give
that user ownership of all the objects, specify <option>-O</>.
</para>
<para>
This option is only meaningful for the plain-text format. For
the other formats, you may specify the option when you
call <command>pg_restore</command>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-R</option></term>
<term><option>--no-reconnect</option></term>
<listitem>
<para>
This option is obsolete but still accepted for backwards
compatibility.
</para>
</listitem>
</varlistentry>
<term><option>-s</option></term>
<term><option>--schema-only</option></term>
<listitem>
<para>
Dump only the schema (data definitions), no data.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-S <replaceable class="parameter">username</replaceable></option></term>
<term><option>--superuser=<replaceable class="parameter">username</replaceable></option></term>
<listitem>
<para>
Specify the superuser user name to use when disabling triggers.
This is only relevant if <option>--disable-triggers</> is used.
(Usually, it's better to leave this out, and instead start the
resulting script as superuser.)
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-t <replaceable class="parameter">table</replaceable></option></term>
<term><option>--table=<replaceable class="parameter">table</replaceable></option></term>
<listitem>
<para>
Dump data for <replaceable class="parameter">table</replaceable>
only. It is possible for there to be
multiple tables with the same name in different schemas; if that
is the case, all matching tables will be dumped. Specify both
<option>--schema</> and <option>--table</> to select just one table.
</para>
<note>
<para>
In this mode, <application>pg_dump</application> makes no
attempt to dump any other database objects that the selected table
may depend upon. Therefore, there is no guarantee
that the results of a single-table dump can be successfully
restored by themselves into a clean database.
</para>
</note>
</listitem>
</varlistentry>
<term><option>-v</></term>
<term><option>--verbose</></term>
<listitem>
<para>
Specifies verbose mode. This will cause
<application>pg_dump</application> to print progress messages
to standard error.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-x</></term>
<term><option>--no-privileges</></term>
<term><option>--no-acl</></term>
<listitem>
<para>
Prevent dumping of access privileges (grant/revoke commands).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-X use-set-session-authorization</></term>
<term><option>--use-set-session-authorization</></term>
<listitem>
<para>
This option is obsolete but still accepted for backwards
compatibility.
<application>pg_dump</application> now always behaves in the
way formerly selected by this option.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-X disable-triggers</></term>
<term><option>--disable-triggers</></term>
<listitem>
<para>
This option is only relevant when creating a data-only dump.
It instructs <application>pg_dump</application> to include commands
to temporarily disable triggers on the target tables while
the data is reloaded. Use this if you have referential
integrity checks or other triggers on the tables that you
do not want to invoke during data reload.
</para>
<para>
Presently, the commands emitted for <option>--disable-triggers</>
must be done as superuser. So, you should also specify
a superuser name with <option>-S</>, or preferably be careful to
start the resulting script as a superuser.
</para>
<para>
This option is only meaningful for the plain-text format. For
the other formats, you may specify the option when you
call <command>pg_restore</command>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-Z <replaceable class="parameter">0..9</replaceable></option></term>
<term><option>--compress=<replaceable class="parameter">0..9</replaceable></option></term>
<listitem>
<para>
Specify the compression level to use in archive formats that
support compression. (Currently only the custom archive
format supports compression.)
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
The following command-line options control the database connection parameters.
<variablelist>
<varlistentry>
<term><option>-h <replaceable class="parameter">host</replaceable></option></term>
<term><option>--host=<replaceable class="parameter">host</replaceable></option></term>
<listitem>
<para>
Specifies the host name of the machine on which the server is
running. If the value begins with a slash, it is used as the
directory for the Unix domain socket. The default is taken
from the <envar>PGHOST</envar> environment variable, if set,
else a Unix domain socket connection is attempted.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-p <replaceable class="parameter">port</replaceable></option></term>
<term><option>--port=<replaceable class="parameter">port</replaceable></option></term>
<listitem>
<para>
Specifies the TCP port or local Unix domain socket file
extension on which the server is listening for connections.
Defaults to the <envar>PGPORT</envar> environment variable, if
set, or a compiled-in default.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-U <replaceable>username</replaceable></option></term>
<listitem>
<para>
Connect as the given user
</para>
</listitem>
</varlistentry>
<varlistentry>
<listitem>
<para>
Force a password prompt. This should happen automatically if
the server requires password authentication.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
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</refsect1>
<refsect1>
<title>Environment</title>
<variablelist>
<varlistentry>
<term><envar>PGDATABASE</envar></term>
<term><envar>PGHOST</envar></term>
<term><envar>PGPORT</envar></term>
<term><envar>PGUSER</envar></term>
<listitem>
<para>
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
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<refsect1 id="app-pgdump-diagnostics">
<title>Diagnostics</title>
<para>
<application>pg_dump</application> internally executes
<command>SELECT</command> statements. If you have problems running
<application>pg_dump</application>, make sure you are able to
select information from the database using, for example, <xref
linkend="app-psql">.
</para>
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<refsect1 id="pg-dump-notes">
<title>Notes</title>
<para>
If your database cluster has any local additions to the <literal>template1</> database,
be careful to restore the output of <application>pg_dump</application> into a
truly empty database; otherwise you are likely to get errors due to
duplicate definitions of the added objects. To make an empty database
without any local additions, copy from <literal>template0</> not <literal>template1</>,
for example:
<programlisting>
CREATE DATABASE foo WITH TEMPLATE template0;
</programlisting>
</para>
<application>pg_dump</application> has a few limitations:
<itemizedlist>
<listitem>
<para>
When dumping a single table or as plain text, <application>pg_dump</application>
does not handle large objects. Large objects must be dumped with the
entire database using one of the non-text archive formats.
</para>
</listitem>
<listitem>
<para>
When a data-only dump is chosen and the option
<option>--disable-triggers</> is used,
<application>pg_dump</application> emits commands to disable
triggers on user tables before inserting the data and commands
to re-enable them after the data has been inserted. If the
restore is stopped in the middle, the system catalogs may be
left in the wrong state.
</para>
</listitem>
</itemizedlist>
</para>
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<para>
Members of tar archives are limited to a size less than 8 GB.
(This is an inherent limitation of the tar file format.) Therefore
this format cannot be used if the textual representation of a table
exceeds that size. The total size of a tar archive and any of the
other output formats is not limited, except possibly by the
operating system.
</para>
The dump file produced by <application>pg_dump</application> does
not contain the statistics used by the optimizer to make query
planning decisions. Therefore, it is wise to run
<command>ANALYZE</command> after restoring from a dump file to
ensure good performance.
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<refsect1 id="pg-dump-examples">
<title>Examples</title>
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<para>
To dump a database:
<screen>
<prompt>$</prompt> <userinput>pg_dump mydb > db.out</userinput>
</screen>
</para>
<para>
To reload this database:
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<screen>
<prompt>$</prompt> <userinput>psql -d database -f db.out</userinput>
</screen>
<para>
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To dump a database called <literal>mydb</> that contains
large objects to a <filename>tar</filename> file:
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<screen>
<prompt>$</prompt> <userinput>pg_dump -Ft -b mydb > db.tar</userinput>
</screen>
</para>
<para>
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To reload this database (with large objects) to an
existing database called <literal>newdb</>:
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<screen>
<prompt>$</prompt> <userinput>pg_restore -d newdb db.tar</userinput>
</screen>
</para>
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<refsect1>
<title>History</title>
<para>
The <application>pg_dump</application> utility first appeared in
<application>Postgres95</application> release 0.02. The
non-plain-text output formats were introduced in
<productname>PostgreSQL</productname> release 7.1.
</para>
</refsect1>
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<refsect1>
<title>See Also</title>
<simplelist type="inline">
<member><xref linkend="app-pg-dumpall"></member>
<member><xref linkend="app-pgrestore"></member>
<member><xref linkend="app-psql"></member>
</simplelist>
</refsect1>
</refentry>
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