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<!--
$Header: /cvsroot/pgsql/doc/src/sgml/ref/pg_dump.sgml,v 1.38 2001/10/23 22:11:22 tgl Exp $
Postgres documentation
-->
<refentry id="APP-PGDUMP">
<docinfo>
<date>2001-03-06</date>
</docinfo>
<refmeta>
<refentrytitle>
pg_dump
</refentrytitle>
<manvolnum>1</manvolnum>
<refmiscinfo>Application</refmiscinfo>
</refmeta>
<refnamediv>
<refname>pg_dump</refname>
<refpurpose>
extract a <productname>PostgreSQL</productname> database into a script file or other archive file
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>pg_dump</command>
<group> <arg>-a</arg> <arg>-s</arg> </group>
<arg>-b</arg>
<arg>-c</arg>
<arg>-C</arg>
<group> <arg>-d</arg> <arg>-D</arg> </group>
<arg>-f <replaceable>file</replaceable></arg>
<arg>-F <replaceable>format</replaceable></arg>
<arg>-i</arg>
<group> <arg>-n</arg> <arg>-N</arg> </group>
<arg>-o</arg>
<arg>-O</arg>
<arg>-R</arg>
<arg>-S</arg>
<arg>-t <replaceable>table</replaceable></arg>
<arg>-v</arg>
<arg>-x</arg>
<arg>-X <replaceable>keyword</replaceable></arg>
<arg>-Z <replaceable>0...9</replaceable></arg>
<arg>-h <replaceable>host</replaceable></arg>
<arg>-p <replaceable>port</replaceable></arg>
<arg>-U <replaceable>username</replaceable></arg>
<arg>-W</arg>
<arg choice="plain"><replaceable>dbname</replaceable></arg>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1 id="pg-dump-description">
<title>
Description
</title>
<para>
<command>pg_dump</command> is a utility for saving a
<productname>PostgreSQL</productname> database into a script or an
archive file. 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. They can be used to
reconstruct the database even on other machines and other
architectures, with some modifications even on other RDBMS
products. The alternative archive file formats are meant to be
used with <xref linkend="app-pgrestore"> to rebuild the database,
and they also allow <command>pg_restore</command> 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.
</para>
<para>
<command>pg_dump</command> will save the information necessary to
re-generate all user-defined types, functions, tables, indexes,
aggregates, and operators. In addition, all the data is copied out
in text format so that it can be readily copied in again, as well
as imported into tools for editing.
</para>
<para>
<command>pg_dump</command>
is useful for dumping out the contents of a database to move from one
<productname>Postgres</productname> installation to another.
</para>
<para>
When used with one of the archive file formats and combined with
<xref linkend="app-pgrestore">, <command>pg_dump</command> provides a
flexible archival and
transfer mechanism. <command>pg_dump</command> can be used to
backup an entire database, then <command>pg_restore</command> 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
<filename>tar</filename> 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 <filename>tar</filename>.
</para>
<para>
While running <command>pg_dump</command>, one should examine the
output for any warnings (printed on standard error), especially in
light of the limitations listed below.
</para>
<para>
<command>pg_dump</command> makes consistent backups even if the
database is being used concurrently. <command>pg_dump</command>
does not block other users accessing the database (readers or
writers).
</para>
<refsect2 id="pg-dump-options">
<title>Options</title>
<para>
<command>pg_dump</command> accepts the following command
line arguments. (Long option forms are only available on some platforms.)
<variablelist>
<varlistentry>
<term><replaceable class="parameter">dbname</replaceable></term>
<listitem>
<para>
Specifies the name of the database to be dumped.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-a</term>
<term>--data-only</term>
<listitem>
<para>
Dump only the data, not the schema (data definitions).
</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>-b</term>
<term>--blobs</term>
<listitem>
<para>
Include large objects in dump.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-c</term>
<term>--clean</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>-C</term>
<term>--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>
<varlistentry>
<term>-d</term>
<term>--inserts</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 RDBMS
packages.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-D</term>
<term>--column-inserts</term>
<term>--attribute-inserts</term>
<listitem>
<para>
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 column ordering.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-f <replaceable class="parameter">file</replaceable></term>
<term>--file=<replaceable class="parameter">file</replaceable></term>
<listitem>
<para>
Send output to the specified file. If this is omitted, the
standard output is used.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-F <replaceable class="parameter">format</replaceable></term>
<term>--format=<replaceable class="parameter">format</replaceable></term>
<listitem>
<para>
Selects the format of the output.
<replaceable>format</replaceable> can be one of the following:
<variablelist>
<varlistentry>
<term>p</term>
<listitem>
<para>
output a plain text <acronym>SQL</acronym> script file (default)
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>t</term>
<listitem>
<para>
output a <filename>tar</filename> archive suitable for input into
<command>pg_restore</command>. 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>c</term>
<listitem>
<para>
output a custom archive suitable for input into
<command>pg_restore</command>. 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>
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-i</term>
<term>--ignore-version</term>
<listitem>
<para>
Ignore version mismatch between <command>pg_dump</command>
and the database server. Since <command>pg_dump</command>
knows a great deal about system catalogs, any given version of
<command>pg_dump</command> is only intended to work with
the corresponding release of the database server. Use this option
if you need to override the version check (and if
<command>pg_dump</command> then fails, don't
say you weren't warned).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-n</term>
<term>--no-quotes</term>
<listitem>
<para>
Suppress double quotes around identifiers unless absolutely necessary.
This may cause trouble loading this dumped data if there are reserved words
used for identifiers.
This was the default behavior for
<command>pg_dump</command> prior to version 6.4.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-N</term>
<term>--quotes</term>
<listitem>
<para>
Include double quotes around identifiers.
This is the default.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-o</term>
<term>--oids</term>
<listitem>
<para>
Dump object identifiers (<acronym>OID</acronym>s) for every
table. Use this option if your application references the OID
columns in some way (e.g., in a foreign key constraint).
Otherwise, this option should not be used.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-O</term>
<term>--no-owner</term>
<listitem>
<para>
Do not output commands to set the
object ownership to match the original database. Typically,
<command>pg_dump</command> issues
(<command>psql</command>-specific) <command>\connect</command>
statements to set ownership of schema elements. See also
under <option>-R</option> and <option>-X
use-set-session-authorization</option>. Note that
<option>-O</option> does not prevent all reconnections to the
database, only the ones that are exclusively used for
ownership adjustments.
</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>-R</term>
<term>--no-reconnect</term>
<listitem>
<para>
Prohibit <command>pg_dump</command>
from outputting a script that would require reconnections to
the database while being restored. An average restoration
script usually has to reconnect several times as different
users to set the original ownerships of the objects. This
option is a rather blunt instrument because it makes
<command>pg_dump</command> lose this ownership information,
<emphasis>unless</emphasis> you use the <option>-X
use-set-session-authorization</option> option.
</para>
<para>
One possible reason why reconnections during restore might not
be desired is if the access to the database requires manual
interaction (e.g., passwords).
</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>-s</term>
<term>--schema-only</term>
<listitem>
<para>
Dump only the schema (data definitions), no data.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-S <replaceable class="parameter">username</replaceable></term>
<term>--superuser=<replaceable class="parameter">username</replaceable></term>
<listitem>
<para>
The scripts or archives created by <command>pg_dump</command>
need to have superuser access in certain cases, such as when
disabling triggers or setting ownership of schema elements.
This option specifies the user name to use for those cases.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-t <replaceable class="parameter">table</replaceable></term>
<term>--table=<replaceable class="parameter">table</replaceable></term>
<listitem>
<para>
Dump data for <replaceable class="parameter">table</replaceable> only.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-v</term>
<term>--verbose</term>
<listitem>
<para>
Specifies verbose mode.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-x</term>
<term>--no-privileges</term>
<term>--no-acl</term>
<listitem>
<para>
Prevent dumping of access privileges (grant/revoke commands).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-X use-set-session-authorization</term>
<term>--use-set-session-authorization</term>
<listitem>
<para>
Normally, if a (plain text mode) script generated by
<command>pg_dump</command> must alter the current database
user (e.g., to set correct object ownerships), it uses the
<xref linkend="app-psql"> <command>\connect</command> command.
This command actually opens a new connection, which might
require manual interaction (e.g., passwords). If you use the
<option>-X use-set-session-authorization</option>, then
<command>pg_dump</command> will instead output <xref
linkend="sql-set-session-authorization"> commands. This has
the same effect, but it requires that the user restoring the
database from the generated script be a database superuser.
This option effectively overrides the <option>-R</option>
option.
</para>
<para>
Since <xref linkend="sql-set-session-authorization"> is a
standard SQL command, whereas <command>\connect</command> only
works in <xref linkend="app-psql">, this option also enhances
the theoretical portability of the output 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>
<varlistentry>
<term>-Z <replaceable class="parameter">0..9</replaceable></term>
<term>--compress=<replaceable class="parameter">0..9</replaceable></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>
<para>
<command>pg_dump</command> also accepts
the following command line arguments for connection parameters:
<variablelist>
<varlistentry>
<term>-h <replaceable class="parameter">host</replaceable></term>
<term>--host=<replaceable class="parameter">host</replaceable></term>
<listitem>
<para>
Specifies the host name of the machine on which the
<command>postmaster</command>
is running. If host begins with a slash, it is used
as the directory for the Unix domain socket.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-p <replaceable class="parameter">port</replaceable></term>
<term>--port=<replaceable class="parameter">port</replaceable></term>
<listitem>
<para>
Specifies the Internet TCP/IP port or local Unix domain socket file
extension on which the <command>postmaster</command>
is listening for connections. The port number defaults to 5432,
or the value of the <envar>PGPORT</envar>
environment variable (if set).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-U <replaceable>username</replaceable></term>
<listitem>
<para>
Connect as the given user.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-W</term>
<listitem>
<para>
Force a password prompt. This should happen automatically if
the server requires password authentication.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
</refsect1>
<refsect1 id="app-pgdump-diagnostics">
<title>Diagnostics</title>
<msgset>
<msgentry>
<msg>
<msgmain>
<msgtext>
<screen><computeroutput>
Connection to database 'template1' failed.
connectDBStart() -- connect() failed: No such file or directory
Is the postmaster running locally
and accepting connections on Unix socket '/tmp/.s.PGSQL.5432'?
</computeroutput></screen>
</msgtext>
</msgmain>
</msg>
<msgexplan>
<para>
<command>pg_dump</command> could not attach to the
<command>postmaster</command>
process on the specified host and port. If you see this message,
ensure that the <command>postmaster</command>
is running on the proper host and that you have specified the proper
port.
</para>
</msgexplan>
</msgentry>
</msgset>
<note>
<para>
<command>pg_dump</command> internally executes
<command>SELECT</command> statements. If you have problems running
<command>pg_dump</command>,
make sure you are able to select information from the database using, for
example, <xref linkend="app-psql">.
</para>
</note>
</refsect1>
<refsect1 id="pg-dump-notes">
<title>Notes</title>
<para>
<command>pg_dump</command> has a few limitations.
<itemizedlist>
<listitem>
<para>
When dumping a single table or as plain text, <command>pg_dump</command>
does not handle large objects. Large objects must be dumped in their
entirety using one of the binary archive formats.
</para>
</listitem>
<listitem>
<para>
When doing a data only dump, <command>pg_dump</command> emits queries
to disable triggers on user tables before inserting the data and queries 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>
</refsect1>
<refsect1 id="pg-dump-examples">
<title>Examples</title>
<para>
To dump a database:
<screen>
<prompt>$</prompt> <userinput>pg_dump mydb > db.out</userinput>
</screen>
</para>
<para>
To reload this database:
<screen>
<prompt>$</prompt> <userinput>psql -d database -f db.out</userinput>
</screen>
</para>
<para>
To dump a database called <literal>mydb</> that contains
large objects to a <filename>tar</filename> file:
<screen>
<prompt>$</prompt> <userinput>pg_dump -Ft -b mydb > db.tar</userinput>
</screen>
</para>
<para>
To reload this database (with large objects) to an
existing database called <literal>newdb</>:
<screen>
<prompt>$</prompt> <userinput>pg_restore -d newdb db.tar</userinput>
</screen>
</para>
</refsect1>
<refsect1>
<title>History</title>
<para>
The <command>pg_dump</command> utility first appeared in
<application>Postgres95 release 0.02</application>. The
non-plain-text output formats were introduced in
<application>PostgreSQL 7.1</application>.
</para>
</refsect1>
<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>
<member><citetitle>PostgreSQL Administrator's Guide</citetitle></member>
</simplelist>
</refsect1>
</refentry>
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