path: root/doc/src/sgml/ref/pg_dump.sgml

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<refentry id="APP-PGDUMP">
 <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>

 <indexterm zone="app-pgdump">
  <primary>pg_dump</primary>
 </indexterm>

 <refsynopsisdiv>
  <cmdsynopsis>
   <command>pg_dump</command>
   <arg rep="repeat"><replaceable>option</replaceable></arg>
   <arg><replaceable>dbname</replaceable></arg>
  </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).
  </para>

  <para>
   Dumps can be output in script or archive file formats. Script
   dumps are plain-text files containing the SQL commands required
   to reconstruct the database to the state it was in at the time it was
   saved. To restore from such a script, feed it to <xref
   linkend="app-psql">. Script files
   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 must be used with
   <xref linkend="app-pgrestore"> to rebuild the database.  They
   allow <application>pg_restore</application> to be selective about
   what is restored, or even to reorder the items prior to being
   restored.
   The archive file formats are designed to be portable across
   architectures.
  </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 standard Unix 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>

 <refsect1 id="pg-dump-options">
  <title>Options</title>

  <para>
    The following command-line options control the content and
    format of the output.

    <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).
       </para>

       <para>
        This option is only meaningful for the plain-text format.  For
        the archive formats, you may specify the option when you
        call <command>pg_restore</command>.
       </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 archive 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 archive formats, you may specify the option when you
        call <command>pg_restore</command>.
       </para>
      </listitem>
     </varlistentry>

     <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;
        it is mainly useful for making dumps that can be loaded into
        non-<productname>PostgreSQL</productname> databases.  Note that
        the restore may fail altogether if you have rearranged column order.
        The <option>-D</option> option is safer, though even slower.
        Also, while this option generates errors for invalid data, 
        it allows other <command>INSERT</command>s to continue loading
        data into the table.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-D</option></term>
      <term><option>--column-inserts</option></term>
      <term><option>--attribute-inserts</option></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; it is mainly
        useful for making dumps that can be loaded into
        non-<productname>PostgreSQL</productname> databases.
        Also, while this option generates errors for invalid data, 
        it allows other <command>INSERT</command>s to continue loading
        data into the table.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-E <replaceable class="parameter">encoding</replaceable></option></term>
      <term><option>--encoding=<replaceable class="parameter">encoding</replaceable></option></term>
      <listitem>
       <para>
        Create the dump in the specified character set encoding. By default,
        the dump is created in the database encoding.  (Another way to get the
        same result is to set the <envar>PGCLIENTENCODING</envar> environment
        variable to the desired dump encoding.)
       </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 database objects
         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>
         Output a custom archive suitable for input into 
         <application>pg_restore</application>. This is the most flexible 
         format in that it allows reordering of loading data as well 
         as object definitions. This format is also compressed by default.
          </para>
         </listitem>
        </varlistentry>

       </variablelist>
       </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">schema</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) as part of the
        data 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>ALTER OWNER</> or 
        <command>SET SESSION AUTHORIZATION</command>
        statements to set ownership of created database objects.
        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 archive 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>

     <varlistentry>
      <term><option>-s</option></term>
      <term><option>--schema-only</option></term>
      <listitem>
       <para>
        Dump only the object definitions (schema), not 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>

     <varlistentry>
      <term><option>-v</></term>
      <term><option>--verbose</></term>
      <listitem>
       <para>
        Specifies verbose mode.  This will cause
        <application>pg_dump</application> to output detailed object
        comments and start/stop times to the dump file, and 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 disable-dollar-quoting</></term>
      <term><option>--disable-dollar-quoting</></term>
      <listitem>
       <para>
        This option disables the use of dollar quoting for function bodies,
        and forces them to be quoted using SQL standard string syntax.
       </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 archive formats, you may specify the option when you
        call <command>pg_restore</command>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-X use-set-session-authorization</></term>
      <term><option>--use-set-session-authorization</></term>
      <listitem>
       <para>
        Output SQL-standard <command>SET SESSION AUTHORIZATION</> commands
        instead of <command>ALTER OWNER</> commands to determine object
        ownership.  This makes the dump more standards compatible, but
        depending on the history of the objects in the dump, may not restore
        properly.  Also, a dump using <command>SET SESSION AUTHORIZATION</>
        will certainly require superuser privileges to restore correctly,
        whereas <command>ALTER OWNER</> requires lesser privileges.
       </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>

   <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>
      <term><option>-W</option></term>
      <listitem>
       <para>
        Force a password prompt.  This should happen automatically if
        the server requires password authentication.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>
 </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>
      Default connection parameters.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

 <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>
 </refsect1>


 <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>

  <para>
   <application>pg_dump</application> has a few limitations:

   <itemizedlist>
    <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>

  <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 any one 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>

  <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.
  </para>

  <para>
   Because <application>pg_dump</application> is used to tranfer data
   to newer versions of <productname>PostgreSQL</>, the output of
   <application>pg_dump</application> can be loaded into
   newer <productname>PostgreSQL</> databases.  It also can read older
   <productname>PostgreSQL</> databases.  However, it usually cannot
   read newer <productname>PostgreSQL</> databases or produce dump output
   that can be loaded into older database versions.  To do this, manual
   editing of the dump file might be required.
  </para>

 </refsect1>

 <refsect1 id="pg-dump-examples">
  <title>Examples</title>

  <para>
   To dump a database:
<screen>
<prompt>$</prompt> <userinput>pg_dump mydb &gt; 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</> to a <filename>tar</filename>
   file:

<screen>
<prompt>$</prompt> <userinput>pg_dump -Ft mydb &gt; db.tar</userinput>
</screen>
  </para>

  <para>
   To reload this dump into 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 <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>

 <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>Environment Variables (<xref linkend="libpq-envars">)</member>
  </simplelist>
 </refsect1>

</refentry>

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