<!--
doc/src/sgml/ref/pg_recvlogical.sgml
PostgreSQL documentation
-->

<refentry id="app-pgrecvlogical">
 <indexterm zone="app-pgrecvlogical">
  <primary>pg_recvlogical</primary>
 </indexterm>

 <refmeta>
  <refentrytitle><application>pg_recvlogical</application></refentrytitle>
  <manvolnum>1</manvolnum>
  <refmiscinfo>Application</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>pg_recvlogical</refname>
  <refpurpose>control <productname>PostgreSQL</productname> logical decoding streams</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
  <cmdsynopsis>
   <command>pg_recvlogical</command>
   <arg rep="repeat" choice="opt"><replaceable>option</replaceable></arg>
  </cmdsynopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>
  <para>
   <command>pg_recvlogical</command> controls logical decoding replication
   slots and streams data from such replication slots.
  </para>

  <para>
   It creates a replication-mode connection, so it is subject to the same
   constraints as <xref linkend="app-pgreceivewal"/>, plus those for logical
   replication (see <xref linkend="logicaldecoding"/>).
  </para>

  <para>
   <command>pg_recvlogical</command> has no equivalent to the logical decoding
   SQL interface's peek and get modes. It sends replay confirmations for
   data lazily as it receives it and on clean exit. To examine pending data on
    a slot without consuming it, use
   <link linkend="functions-replication"><function>pg_logical_slot_peek_changes</function></link>.
  </para>

  <para>
   In the absence of fatal errors, <application>pg_recvlogical</application>
   will run until terminated by the <systemitem>SIGINT</systemitem>
   (<keycombo action="simul"><keycap>Control</keycap><keycap>C</keycap></keycombo>)
   or <systemitem>SIGTERM</systemitem> signal.
  </para>

  <para>
   When <application>pg_recvlogical</application> receives
   a <systemitem>SIGHUP</systemitem> signal, it closes the current output file
   and opens a new one using the filename specified by
   the <option>--file</option> option.  This allows us to rotate
   the output file by first renaming the current file and then sending
   a <systemitem>SIGHUP</systemitem> signal to
   <application>pg_recvlogical</application>.
  </para>
 </refsect1>

 <refsect1>
  <title>Options</title>

   <para>
    At least one of the following options must be specified to select an action:

    <variablelist>

     <varlistentry>
      <term><option>--create-slot</option></term>
      <listitem>
       <para>
        Create a new logical replication slot with the name specified by
        <option>--slot</option>, using the output plugin specified by
        <option>--plugin</option>, for the database specified
        by <option>--dbname</option>.
       </para>

       <para>
        The <option>--two-phase</option> can be specified with
        <option>--create-slot</option> to enable decoding of prepared transactions.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--drop-slot</option></term>
      <listitem>
       <para>
        Drop the replication slot with the name specified
        by <option>--slot</option>, then exit.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--start</option></term>
      <listitem>
       <para>
        Begin streaming changes from the logical replication slot specified
        by <option>--slot</option>, continuing until terminated by a
        signal. If the server side change stream ends with a server shutdown
        or disconnect, retry in a loop unless
        <option>--no-loop</option> is specified.
       </para>

       <para>
        The stream format is determined by the output plugin specified when
        the slot was created.
       </para>

       <para>
        The connection must be to the same database used to create the slot.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>

   <para>
    <option>--create-slot</option> and <option>--start</option> can be
    specified together.  <option>--drop-slot</option> cannot be combined with
    another action.
   </para>

   <para>
    The following command-line options control the location and format of the
    output and other replication behavior:

    <variablelist>
     <varlistentry>
      <term><option>-E <replaceable>lsn</replaceable></option></term>
      <term><option>--endpos=<replaceable>lsn</replaceable></option></term>
      <listitem>
       <para>
        In <option>--start</option> mode, automatically stop replication
        and exit with normal exit status 0 when receiving reaches the
        specified LSN.  If specified when not in <option>--start</option>
        mode, an error is raised.
       </para>

       <para>
        If there's a record with LSN exactly equal to <replaceable>lsn</replaceable>,
        the record will be output.
       </para>

       <para>
        The <option>--endpos</option> option is not aware of transaction
        boundaries and may truncate output partway through a transaction.
        Any partially output transaction will not be consumed and will be
        replayed again when the slot is next read from. Individual messages
        are never truncated.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-f <replaceable>filename</replaceable></option></term>
      <term><option>--file=<replaceable>filename</replaceable></option></term>
      <listitem>
       <para>
        Write received and decoded transaction data into this
        file. Use <literal>-</literal> for <systemitem>stdout</systemitem>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-F <replaceable>interval_seconds</replaceable></option></term>
      <term><option>--fsync-interval=<replaceable>interval_seconds</replaceable></option></term>
      <listitem>
       <para>
        Specifies how often <application>pg_recvlogical</application> should
        issue <function>fsync()</function> calls to ensure the output file is
        safely flushed to disk.
       </para>

       <para>
        The server will occasionally request the client to perform a flush and
        report the flush position to the server.  This setting is in addition
        to that, to perform flushes more frequently.
       </para>

       <para>
        Specifying an interval of <literal>0</literal> disables
        issuing <function>fsync()</function> calls altogether, while still
        reporting progress to the server.  In this case, data could be lost in
        the event of a crash.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-I <replaceable>lsn</replaceable></option></term>
      <term><option>--startpos=<replaceable>lsn</replaceable></option></term>
      <listitem>
       <para>
        In <option>--start</option> mode, start replication from the given
        LSN.  For details on the effect of this, see the documentation
        in <xref linkend="logicaldecoding"/>
        and <xref linkend="protocol-replication"/>. Ignored in other modes.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--if-not-exists</option></term>
      <listitem>
       <para>
        Do not error out when <option>--create-slot</option> is specified
        and a slot with the specified name already exists.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-n</option></term>
      <term><option>--no-loop</option></term>
      <listitem>
       <para>
        When the connection to the server is lost, do not retry in a loop, just exit.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-o <replaceable>name</replaceable>[=<replaceable>value</replaceable>]</option></term>
      <term><option>--option=<replaceable>name</replaceable>[=<replaceable>value</replaceable>]</option></term>
      <listitem>
       <para>
        Pass the option <replaceable>name</replaceable> to the output plugin with,
        if specified, the option value <replaceable>value</replaceable>. Which
        options exist and their effects depends on the used output plugin.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-P <replaceable>plugin</replaceable></option></term>
      <term><option>--plugin=<replaceable>plugin</replaceable></option></term>
      <listitem>
       <para>
        When creating a slot, use the specified logical decoding output
        plugin. See <xref linkend="logicaldecoding"/>. This option has no
        effect if the slot already exists.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-s <replaceable>interval_seconds</replaceable></option></term>
      <term><option>--status-interval=<replaceable>interval_seconds</replaceable></option></term>
      <listitem>
       <para>
        This option has the same effect as the option of the same name
        in <xref linkend="app-pgreceivewal"/>.  See the description there.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-S <replaceable>slot_name</replaceable></option></term>
      <term><option>--slot=<replaceable>slot_name</replaceable></option></term>
      <listitem>
       <para>
        In <option>--start</option> mode, use the existing logical replication slot named
        <replaceable>slot_name</replaceable>. In <option>--create-slot</option>
        mode, create the slot with this name. In <option>--drop-slot</option>
        mode, delete the slot with this name.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
       <term><option>-t</option></term>
       <term><option>--two-phase</option></term>
       <listitem>
       <para>
        Enables decoding of prepared transactions. This option may only be specified with
        <option>--create-slot</option>.
       </para>
       </listitem>
     </varlistentry>

     <varlistentry>
       <term><option>-v</option></term>
       <term><option>--verbose</option></term>
       <listitem>
       <para>
        Enables verbose mode.
       </para>
       </listitem>
     </varlistentry>
    </variablelist>
   </para>

   <para>
    The following command-line options control the database connection parameters.

    <variablelist>
      <varlistentry>
       <term><option>-d <replaceable>dbname</replaceable></option></term>
       <term><option>--dbname=<replaceable>dbname</replaceable></option></term>
       <listitem>
        <para>
         The database to connect to.  See the description
         of the actions for what this means in detail.
         The <replaceable>dbname</replaceable> can be a <link
         linkend="libpq-connstring">connection string</link>.  If so,
         connection string parameters will override any conflicting
         command line options.  Defaults to the user name.
        </para>
       </listitem>
      </varlistentry>

      <varlistentry>
       <term><option>-h <replaceable>hostname-or-ip</replaceable></option></term>
       <term><option>--host=<replaceable>hostname-or-ip</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>port</replaceable></option></term>
       <term><option>--port=<replaceable>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>user</replaceable></option></term>
       <term><option>--username=<replaceable>user</replaceable></option></term>
       <listitem>
        <para>
         User name to connect as.  Defaults to current operating system user
         name.
        </para>
       </listitem>
      </varlistentry>

      <varlistentry>
       <term><option>-w</option></term>
       <term><option>--no-password</option></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_recvlogical</application> to prompt for a
         password before connecting to a database.
        </para>

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

   <para>
    The following additional options are available:

    <variablelist>
     <varlistentry>
       <term><option>-V</option></term>
       <term><option>--version</option></term>
       <listitem>
       <para>
        Print the <application>pg_recvlogical</application> version and exit.
       </para>
       </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-?</option></term>
      <term><option>--help</option></term>
       <listitem>
        <para>
         Show help about <application>pg_recvlogical</application> command line
         arguments, and exit.
        </para>
       </listitem>
      </varlistentry>
    </variablelist>
   </para>
 </refsect1>

 <refsect1>
  <title>Exit Status</title>
  <para>
   <application>pg_recvlogical</application> will exit with status 0 when
   terminated by the <systemitem>SIGINT</systemitem> or
   <systemitem>SIGTERM</systemitem> signal.  (That is the
   normal way to end it.  Hence it is not an error.)  For fatal errors or
   other signals, the exit status will be nonzero.
  </para>
 </refsect1>

 <refsect1>
  <title>Environment</title>

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

  <para>
   The environment variable <envar>PG_COLOR</envar> specifies whether to use
   color in diagnostic messages. Possible values are
   <literal>always</literal>, <literal>auto</literal> and
   <literal>never</literal>.
  </para>
 </refsect1>

 <refsect1>
  <title>Notes</title>

  <para>
   <application>pg_recvlogical</application> will preserve group permissions on
   the received WAL files if group permissions are enabled on the source
   cluster.
  </para>

 </refsect1>

 <refsect1>
  <title>Examples</title>

  <para>
   See <xref linkend="logicaldecoding-example"/> for an example.
  </para>
 </refsect1>

 <refsect1>
  <title>See Also</title>

  <simplelist type="inline">
   <member><xref linkend="app-pgreceivewal"/></member>
  </simplelist>
 </refsect1>
</refentry>
