Create a "sort support" interface API for faster sorting.

[postgresql] / doc / src / sgml / ref / pg_dump.sgml

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doc/src/sgml/ref/pg_dump.sgml
PostgreSQL documentation
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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>connection-option</replaceable></arg>
   <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.
  </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 can specify the option when you
        call <command>pg_restore</command>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-b</></term>
      <term><option>--blobs</></term>
      <listitem>
       <para>
        Include large objects in the dump.  This is the default behavior
        except when <option>--schema</>, <option>--table</>, or
        <option>--schema-only</> is specified, so the <option>-b</>
        switch is only useful to add large objects to selective dumps.
       </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 outputting the commands for creating them.
        (Restore might generate some harmless errors.)
       </para>

       <para>
        This option is only meaningful for the plain-text format.  For
        the archive formats, you can 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 can specify the option when you
        call <command>pg_restore</command>.
       </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. This parameter can be omitted for
        file based output formats, in which case the standard output is used.
        It must be given for the directory output format however, where it
        specifies the target directory instead of a file. In this case the
        directory is created by <command>pg_dump</command> and must not exist
        before.
       </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>
         <term><literal>plain</></term>
         <listitem>
          <para>
           Output a plain-text <acronym>SQL</acronym> script file (the default).
          </para>
         </listitem>
        </varlistentry>

        <varlistentry>
         <term><literal>c</></term>
         <term><literal>custom</></term>
         <listitem>
          <para>
           Output a custom-format archive suitable for input into
           <application>pg_restore</application>.
           Together with the directory output format, this is the most flexible
           output format in that it allows manual selection and reordering of
           archived items during restore. This format is also compressed by
           default.
          </para>
         </listitem>
        </varlistentry>

        <varlistentry>
         <term><literal>d</></term>
         <term><literal>directory</></term>
         <listitem>
          <para>
           Output a directory-format archive suitable for input into
           <application>pg_restore</application>. This will create a directory
           with one file for each table and blob being dumped, plus a
           so-called Table of Contents file describing the dumped objects in a
           machine-readable format that <application>pg_restore</application>
           can read. A directory format archive can be manipulated with
           standard Unix tools; for example, files in an uncompressed archive
           can be compressed with the <application>gzip</application> tool.
           This format is compressed by default.
          </para>
         </listitem>
        </varlistentry>

        <varlistentry>
         <term><literal>t</></term>
         <term><literal>tar</></term>
         <listitem>
          <para>
           Output a <command>tar</command>-format archive suitable for input
           into <application>pg_restore</application>. The tar-format is
           compatible with the directory-format; extracting a tar-format
           archive produces a valid directory-format archive.
           However, the tar-format does not support compression and has a
           limit of 8 GB on the size of individual tables. Also, the relative
           order of table data items cannot be changed during restore.
          </para>
         </listitem>
        </varlistentry>
       </variablelist></para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-i</></term>
      <term><option>--ignore-version</></term>
      <listitem>
       <para>
        A deprecated option that is now ignored.
       </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 only schemas matching <replaceable
        class="parameter">schema</replaceable>; this selects both the
        schema itself, and all its contained objects.  When this option is
        not specified, all non-system schemas in the target database will be
        dumped.  Multiple schemas can be
        selected by writing multiple <option>-n</> switches.  Also, the
        <replaceable class="parameter">schema</replaceable> parameter is
        interpreted as a pattern according to the same rules used by
        <application>psql</>'s <literal>\d</> commands (see <xref
        linkend="APP-PSQL-patterns" endterm="APP-PSQL-patterns-title">),
        so multiple schemas can also be selected by writing wildcard characters
        in the pattern.  When using wildcards, be careful to quote the pattern
        if needed to prevent the shell from expanding the wildcards;  see
        <xref linkend="pg-dump-examples" endterm="pg-dump-examples-title">.
       </para>

       <note>
        <para>
         When <option>-n</> is specified, <application>pg_dump</application>
         makes no attempt to dump any other database objects that the selected
         schema(s) might depend upon. Therefore, there is no guarantee
         that the results of a specific-schema dump can be successfully
         restored by themselves into a clean database.
        </para>
       </note>

       <note>
        <para>
         Non-schema objects such as blobs are not dumped when <option>-n</> is
         specified.  You can add blobs back to the dump with the
         <option>--blobs</> switch.
        </para>
       </note>

      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-N <replaceable class="parameter">schema</replaceable></option></term>
      <term><option>--exclude-schema=<replaceable class="parameter">schema</replaceable></option></term>
      <listitem>
       <para>
        Do not dump any schemas matching the <replaceable
        class="parameter">schema</replaceable> pattern.  The pattern is
        interpreted according to the same rules as for <option>-n</>.
        <option>-N</> can be given more than once to exclude schemas
        matching any of several patterns.
       </para>

       <para>
        When both <option>-n</> and <option>-N</> are given, the behavior
        is to dump just the schemas that match at least one <option>-n</>
        switch but no <option>-N</> switches.  If <option>-N</> appears
        without <option>-n</>, then schemas matching <option>-N</> are
        excluded from what is otherwise a normal dump.
       </para>
      </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 can 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 only tables (or views or sequences or foreign tables) matching
        <replaceable class="parameter">table</replaceable>.  Multiple tables
        can be selected by writing multiple <option>-t</> switches.  Also, the
        <replaceable class="parameter">table</replaceable> parameter is
        interpreted as a pattern according to the same rules used by
        <application>psql</>'s <literal>\d</> commands (see <xref
        linkend="APP-PSQL-patterns" endterm="APP-PSQL-patterns-title">),
        so multiple tables can also be selected by writing wildcard characters
        in the pattern.  When using wildcards, be careful to quote the pattern
        if needed to prevent the shell from expanding the wildcards;  see
        <xref linkend="pg-dump-examples" endterm="pg-dump-examples-title">.
       </para>

       <para>
        The <option>-n</> and <option>-N</> switches have no effect when
        <option>-t</> is used, because tables selected by <option>-t</> will
        be dumped regardless of those switches, and non-table objects will not
        be dumped.
       </para>

       <note>
        <para>
         When <option>-t</> is specified, <application>pg_dump</application>
         makes no attempt to dump any other database objects that the selected
         table(s) might depend upon. Therefore, there is no guarantee
         that the results of a specific-table dump can be successfully
         restored by themselves into a clean database.
        </para>
       </note>

       <note>
        <para>
         The behavior of the <option>-t</> switch is not entirely upward
         compatible with pre-8.2 <productname>PostgreSQL</productname>
         versions.  Formerly, writing <literal>-t tab</> would dump all
         tables named <literal>tab</>, but now it just dumps whichever one
         is visible in your default search path.  To get the old behavior
         you can write <literal>-t '*.tab'</>.  Also, you must write something
         like <literal>-t sch.tab</> to select a table in a particular schema,
         rather than the old locution of <literal>-n sch -t tab</>.
        </para>
       </note>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-T <replaceable class="parameter">table</replaceable></option></term>
      <term><option>--exclude-table=<replaceable class="parameter">table</replaceable></option></term>
      <listitem>
       <para>
        Do not dump any tables matching the <replaceable
        class="parameter">table</replaceable> pattern.  The pattern is
        interpreted according to the same rules as for <option>-t</>.
        <option>-T</> can be given more than once to exclude tables
        matching any of several patterns.
       </para>

       <para>
        When both <option>-t</> and <option>-T</> are given, the behavior
        is to dump just the tables that match at least one <option>-t</>
        switch but no <option>-T</> switches.  If <option>-T</> appears
        without <option>-t</>, then tables matching <option>-T</> are
        excluded from what is otherwise a normal dump.
       </para>
      </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>-V</></term>
       <term><option>--version</></term>
       <listitem>
       <para>
       Print the <application>pg_dump</application> version and exit.
       </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>-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.  Zero means no compression.
        For the custom archive format, this specifies compression of
        individual table-data segments, and the default is to compress
        at a moderate level.
        For plain text output, setting a nonzero compression level causes
        the entire output file to be compressed, as though it had been
        fed through <application>gzip</>; but the default is not to compress.
        The tar archive format currently does not support compression at all.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--binary-upgrade</option></term>
      <listitem>
       <para>
        This option is for use by in-place upgrade utilities.  Its use
        for other purposes is not recommended or supported.  The
        behavior of the option may change in future releases without
        notice.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <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.
        However, since this option generates a separate command for each row,
        an error in reloading a row causes only that row to be lost rather
        than the entire table contents.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <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>--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 can specify the option when you
        call <command>pg_restore</command>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <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.
        However, since this option generates a separate command for each row,
        an error in reloading a row causes only that row to be lost rather
        than the entire table contents.
        Note that
        the restore might fail altogether if you have rearranged column order.
        The <option>--column-inserts</option> option is safe against column
        order changes, though even slower.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--lock-wait-timeout=<replaceable class="parameter">timeout</replaceable></option></term>
      <listitem>
       <para>
        Do not wait forever to acquire shared table locks at the beginning of
        the dump. Instead fail if unable to lock a table within the specified
        <replaceable class="parameter">timeout</>. The timeout may be
        specified in any of the formats accepted by <command>SET
        statement_timeout</>.  (Allowed values vary depending on the server
        version you are dumping from, but an integer number of milliseconds
        is accepted by all versions since 7.3.  This option is ignored when
        dumping from a pre-7.3 server.)
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--no-security-labels</option></term>
      <listitem>
       <para>
        Do not dump security labels.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--no-tablespaces</option></term>
      <listitem>
       <para>
        Do not output commands to select tablespaces.
        With this option, all objects will be created in whichever
        tablespace is the default during restore.
       </para>

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

     <varlistentry>
      <term><option>--no-unlogged-table-data</option></term>
      <listitem>
       <para>
        Do not dump the contents of unlogged tables.  This option has no
        effect on whether or not the table definitions (schema) are dumped;
        it only suppresses dumping the table data.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--quote-all-identifiers</></term>
      <listitem>
       <para>
        Force quoting of all identifiers.  This may be useful when dumping a
        database for migration to a future version that may have introduced
        additional keywords.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--serializable-deferrable</option></term>
      <listitem>
       <para>
        Use a <literal>serializable</literal> transaction for the dump, to
        ensure that the snapshot used is consistent with later database
        states; but do this by waiting for a point in the transaction stream
        at which no anomalies can be present, so that there isn't a risk of
        the dump failing or causing other transactions to roll back with a
        <literal>serialization_failure</literal>.  See <xref linkend="mvcc">
        for more information about transaction isolation and concurrency
        control.
       </para>

       <para>
        This option is not beneficial for a dump which is intended only for
        disaster recovery.  It could be useful for a dump used to load a
        copy of the database for reporting or other read-only load sharing
        while the original database continues to be updated.  Without it the
        dump may reflect a state which is not consistent with any serial
        execution of the transactions eventually committed.  For example, if
        batch processing techniques are used, a batch may show as closed in
        the dump without all of the items which are in the batch appearing.
       </para>

       <para>
        This option will make no difference if there are no read-write
        transactions active when pg_dump is started.  If read-write
        transactions are active, the start of the dump may be delayed for an
        indeterminate length of time.  Once running, performance with or
        without the switch is the same.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <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, might 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>-?</></term>
       <term><option>--help</></term>
       <listitem>
       <para>
       Show help about <application>pg_dump</application> command line
       arguments, and exit.
       </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>
      <term><option>--username=<replaceable class="parameter">username</replaceable></option></term>
      <listitem>
       <para>
        User name to connect as.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-w</></term>
      <term><option>--no-password</></term>
      <listitem>
       <para>
        Never issue a password prompt.  If the server requires
        password authentication and a password is not available by
        other means such as a <filename>.pgpass</filename> file, the
        connection attempt will fail.  This option can be useful in
        batch jobs and scripts where no user is present to enter a
        password.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-W</option></term>
      <term><option>--password</option></term>
      <listitem>
       <para>
        Force <application>pg_dump</application> to prompt for a
        password before connecting to a database.
       </para>

       <para>
        This option is never essential, since
        <application>pg_dump</application> will automatically prompt
        for a password if the server demands password authentication.
        However, <application>pg_dump</application> will waste a
        connection attempt finding out that the server wants a password.
        In some cases it is worth typing <option>-W</> to avoid the extra
        connection attempt.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--role=<replaceable class="parameter">rolename</replaceable></option></term>
      <listitem>
       <para>
        Specifies a role name to be used to create the dump.
        This option causes <application>pg_dump</> to issue a
        <command>SET ROLE</> <replaceable class="parameter">rolename</>
        command after connecting to the database. It is useful when the
        authenticated user (specified by <option>-U</>) lacks privileges
        needed by <application>pg_dump</>, but can switch to a role with
        the required rights.  Some installations have a policy against
        logging in directly as a superuser, and use of this option allows
        dumps to be made without violating the policy.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>
 </refsect1>

 <refsect1>
  <title>Environment</title>

  <variablelist>
   <varlistentry>
    <term><envar>PGDATABASE</envar></term>
    <term><envar>PGHOST</envar></term>
    <term><envar>PGOPTIONS</envar></term>
    <term><envar>PGPORT</envar></term>

    <term><envar>PGUSER</envar></term>
    <listitem>
     <para>
      Default connection parameters.
     </para>
    </listitem>

   </varlistentry>
  </variablelist>

  <para>
   This utility, like most other <productname>PostgreSQL</> utilities,
   also uses the environment variables supported by <application>libpq</>
   (see <xref linkend="libpq-envars">).
  </para>

 </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">.  Also, any default connection settings and environment
   variables used by the <application>libpq</application> front-end
   library will apply.
  </para>

  <para>
   The database activity of <application>pg_dump</application> is
   normally collected by the statistics collector.  If this is
   undesirable, you can set parameter <varname>track_counts</>
   to false via <envar>PGOPTIONS</envar> or the <literal>ALTER
   USER</literal> command.
  </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>
   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 then commands to re-enable them after the data has been
   inserted.  If the restore is stopped in the middle, the system
   catalogs might be left in the wrong state.
  </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 optimal performance; see <xref linkend="vacuum-for-statistics">
   and <xref linkend="autovacuum"> for more information.
   The dump file also does not
   contain any <command>ALTER DATABASE ... SET</> commands;
   these settings are dumped by <xref linkend="app-pg-dumpall">,
   along with database users and other installation-wide settings.
  </para>

  <para>
   Because <application>pg_dump</application> is used to transfer data
   to newer versions of <productname>PostgreSQL</>, the output of
   <application>pg_dump</application> can be expected to load into
   <productname>PostgreSQL</> server versions newer than
   <application>pg_dump</>'s version.  <application>pg_dump</> can also
   dump from <productname>PostgreSQL</> servers older than its own version.
   (Currently, servers back to version 7.0 are supported.)
   However, <application>pg_dump</> cannot dump from
   <productname>PostgreSQL</> servers newer than its own major version;
   it will refuse to even try, rather than risk making an invalid dump.
   Also, it is not guaranteed that <application>pg_dump</>'s output can
   be loaded into a server of an older major version &mdash; not even if the
   dump was taken from a server of that version.  Loading a dump file
   into an older server may require manual editing of the dump file
   to remove syntax not understood by the older server.
  </para>
 </refsect1>

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

  <para>
   To dump a database called <literal>mydb</> into a SQL-script file:
<screen>
<prompt>$</prompt> <userinput>pg_dump mydb &gt; db.sql</userinput>
</screen>
  </para>

  <para>
   To reload such a script into a (freshly created) database named
   <literal>newdb</>:

<screen>
<prompt>$</prompt> <userinput>psql -d newdb -f db.sql</userinput>
</screen>
  </para>

  <para>
   To dump a database into a custom-format archive file:

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

  <para>
   To dump a database into a directory-format archive:

<screen>
<prompt>$</prompt> <userinput>pg_dump -Fd mydb -f dumpdir</userinput>
</screen>
  </para>

  <para>
   To reload an archive file into a (freshly created) database named
   <literal>newdb</>:

<screen>
<prompt>$</prompt> <userinput>pg_restore -d newdb db.dump</userinput>
</screen>
  </para>

  <para>
   To dump a single table named <literal>mytab</>:

<screen>
<prompt>$</prompt> <userinput>pg_dump -t mytab mydb &gt; db.sql</userinput>
</screen>
  </para>

  <para>
   To dump all tables whose names start with <literal>emp</> in the
   <literal>detroit</> schema, except for the table named
   <literal>employee_log</literal>:

<screen>
<prompt>$</prompt> <userinput>pg_dump -t 'detroit.emp*' -T detroit.employee_log mydb &gt; db.sql</userinput>
</screen>
  </para>

  <para>
   To dump all schemas whose names start with <literal>east</> or
   <literal>west</> and end in <literal>gsm</>, excluding any schemas whose
   names contain the word <literal>test</>:

<screen>
<prompt>$</prompt> <userinput>pg_dump -n 'east*gsm' -n 'west*gsm' -N '*test*' mydb &gt; db.sql</userinput>
</screen>
  </para>

  <para>
   The same, using regular expression notation to consolidate the switches:

<screen>
<prompt>$</prompt> <userinput>pg_dump -n '(east|west)*gsm' -N '*test*' mydb &gt; db.sql</userinput>
</screen>
  </para>

  <para>
   To dump all database objects except for tables whose names begin with
   <literal>ts_</literal>:

<screen>
<prompt>$</prompt> <userinput>pg_dump -T 'ts_*' mydb &gt; db.sql</userinput>
</screen>
  </para>

  <para>
   To specify an upper-case or mixed-case name in <option>-t</> and related
   switches, you need to double-quote the name; else it will be folded to
   lower case (see <xref
   linkend="APP-PSQL-patterns" endterm="APP-PSQL-patterns-title">).  But
   double quotes are special to the shell, so in turn they must be quoted.
   Thus, to dump a single table with a mixed-case name, you need something
   like

<screen>
<prompt>$</prompt> <userinput>pg_dump -t '"MixedCaseName"' mydb &gt; mytab.sql</userinput>
</screen></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>
  </simplelist>
 </refsect1>

</refentry>