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Postgres documentation
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<refentry id="APP-POSTGRES">
 <docinfo>
  <date>2000-11-12</date>
 </docinfo>

 <refmeta>
  <refentrytitle id="APP-POSTGRES-TITLE"><application>postgres</application></refentrytitle>
  <manvolnum>1</manvolnum>
  <refmiscinfo>Application</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>postgres</refname>
  <refpurpose>Run a <productname>PostgreSQL</productname> single-user backend</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
  <cmdsynopsis>
   <!-- standalone call -->
   <command>postgres</command>
   <arg>-A <group choice="plain"><arg>0</arg><arg>1</arg></group></arg>
   <arg>-B <replaceable>nbuffers</replaceable></arg>
   <arg>-c <replaceable>name</replaceable>=<replaceable>value</replaceable></arg>
   <arg>-d <replaceable>debug-level</replaceable></arg>
   <arg>-D <replaceable>datadir</replaceable></arg>
   <arg>-e</arg>
   <arg>-E</arg>
   <arg>-f<group choice="plain"><arg>s</arg><arg>i</arg><arg>t</arg><arg>n</arg><arg>m</arg><arg>h</arg></group></arg>
   <arg>-F</arg>
   <arg>-i</arg>
   <arg>-L</arg>
   <arg>-N</arg>
   <arg>-o <replaceable>file-name</replaceable></arg>
   <arg>-O</arg>
   <arg>-P</arg>
   <group>
    <arg>-s</arg>
    <arg>-t<group choice="plain"><arg>pa</arg><arg>pl</arg><arg>ex</arg></group></arg>
   </group>
   <arg>-S <replaceable>sort-mem</replaceable></arg>
   <arg>-W <replaceable>seconds</replaceable></arg>
   <arg choice="plain"><replaceable>database</replaceable></arg>
   <sbr>
   <!-- postmaster fork -->
   <command>postgres</command>
   <arg>-A <group choice="plain"><arg>0</arg><arg>1</arg></group></arg>
   <arg>-B <replaceable>nbuffers</replaceable></arg>
   <arg>-c <replaceable>name</replaceable>=<replaceable>value</replaceable></arg>
   <arg>-d <replaceable>debug-level</replaceable></arg>
   <arg>-D <replaceable>datadir</replaceable></arg>
   <arg>-e</arg>
   <arg>-f<group choice="plain"><arg>s</arg><arg>i</arg><arg>t</arg><arg>n</arg><arg>m</arg><arg>h</arg></group></arg>
   <arg>-F</arg>
   <arg>-i</arg>
   <arg>-L</arg>
   <arg>-o <replaceable>file-name</replaceable></arg>
   <arg>-O</arg>
   <arg>-p <replaceable>database</replaceable></arg>
   <arg>-P</arg>
   <group>
    <arg>-s</arg>
    <arg>-t<group choice="plain"><arg>pa</arg><arg>pl</arg><arg>ex</arg></group></arg>
   </group>
   <arg>-S <replaceable>sort-mem</replaceable></arg>
   <arg>-v <replaceable>protocol-version</replaceable></arg>
   <arg>-W <replaceable>seconds</replaceable></arg>
  </cmdsynopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   The <filename>postgres</filename> executable is the actual
   <productname>PostgreSQL</productname> server process that processes
   queries.  The second form above is how
   <application>postgres</application> is invoked by the <xref
   linkend="app-postmaster" endterm="app-postmaster-title"> (only
   conceptually, since both <filename>postmaster</filename> and
   <filename>postgres</filename> are in fact the same program); it
   should not be invoked directly this way.  The first form invokes
   the server directly in interactive mode.  The primary use for this
   mode is for bootstrapping by <xref linkend="app-initdb"
   endterm="app-initdb-title">.
  </para>

  <para>
   When invoked in interactive mode from the shell, the user can enter
   queries and the results will be printed to the screen, but in a
   form that is more useful for developers than end users.  But note
   that running a single-user backend is not truly suitable for
   debugging the server since no realistic inter-process communication
   and locking will happen.
  </para>

  <para>
   When running a stand-alone backend the session user name will
   automatically be set to the current effective Unix user name.  If
   that user does not exist the server will not start.
  </para>

  <refsect2>
   <title>Options</title>

   <para>
    When <application>postgres</application> is started by a <xref
    linkend="app-postmaster" endterm="app-postmaster-title"> then it
    inherits all options set by the latter.  Additionally,
    <application>postgres</application>-specific options can be passed
    from the <application>postmaster</application> with the
    <option>-o</option> switch.
   </para>

   <para>
    You can avoid having to type these options by setting up a
    configuration file.  See the <citetitle>Administrator's
    Guide</citetitle> for details.  Some (safe) options can also be
    set from the connecting client in an application-dependent way.
    For example, if the environment variable <envar>PGOPTIONS</envar>
    is set, then libpq-based clients will pass that string to the
    server, which will interpret it as
    <application>postgres</application> command-line options.
   </para>

   <refsect3>
    <title>General Purpose</title>

    <para>
     The options <option>-A</option>, <option>-B</option>,
     <option>-c</option>, <option>-d</option>, <option>-D</option>,
     and <option>-F</option> have the same meaning as with the <xref
     linkend="app-postmaster" endterm="app-postmaster-title">.
    </para>

    <variablelist>
     <varlistentry>
      <term>-e</term>
      <listitem>
       <para>
        Sets the default date style to <quote>European</quote>, which
	means that the <quote>day before month</quote> (rather than
	month before day) rule is used to interpret ambiguous date
	input, and that the day is printed before the month in certain
	date output formats.  See the <citetitle>PostgreSQL User's
	Guide</citetitle> for more information.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>-o <replaceable class="parameter">file-name</replaceable></term>
      <listitem>
       <para>
	Sends all debugging and error output to 
	<replaceable class="parameter">OutputFile</replaceable>.
	If the backend is running under the <application>postmaster</application>,
	error messages are still sent to the frontend process as well as to
	<replaceable class="parameter">OutputFile</replaceable>,
	but debugging output is sent to the controlling tty of the
	<application>postmaster</application>
	(since only one file descriptor can be sent to an actual file).
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>-P</term>
      <listitem>
       <para>
	Ignore system indexes to scan/update system tuples. The
	<command>REINDEX</command> command for system tables/indexes
	requires this option to be used.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>-s</term>
      <listitem>
       <para>
	Print time information and other statistics at the end of each query.
	This is useful for benchmarking or for use in tuning the number of
	buffers.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>-S <replaceable class="parameter">sort-mem</replaceable></term>
      <listitem>
       <para>
	Specifies the amount of memory to be used by internal sorts and hashes
	before resorting to temporary disk files.  The value is specified in
	kilobytes, and defaults to 512 kilobytes.  Note that for a complex query,
	several sorts and/or hashes might be running in parallel, and each one
	will be allowed to use as much as
	<replaceable class="parameter">sort-mem</replaceable> kilobytes
	before it starts to put data into temporary files.
       </para>
      </listitem>
     </varlistentry>

    </variablelist>
   </refsect3>

   <refsect3>
    <title>Options for stand-alone mode</title>

    <variablelist>
     <varlistentry>
      <term><replaceable class="parameter">database</replaceable></term>
      <listitem>
       <para>
	Specifies the name of the database to be accessed.  If it is
	omitted it defaults to the user name.	
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>-E</term>
      <listitem>
       <para>
	Echo all queries.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>-N</term>
      <listitem>
       <para>
	Disables use of newline as a query delimiter.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </refsect3>

   <refsect3>
    <title>Semi-internal Options</title>

    <para>
     There are several other options that may be specified, used
     mainly for debugging purposes.  These are listed here only for
     the use by <productname>PostgreSQL</productname> system
     developers.  <emphasis>Use of any of these options is highly
     discouraged.</emphasis>  Furthermore, any of these options may
     disappear or change in a future release without notice.
   </para>
    <variablelist>

     <varlistentry>
      <term>-f [ s | i | m | n | h ]</term>
      <listitem>
       <para>
	Forbids the use of particular scan and join methods:
	<literal>s</literal> and <literal>i</literal>
	disable sequential and index scans respectively, while
	<literal>n</literal>, <literal>m</literal>, and <literal>h</literal>
	disable nested-loop, merge and hash joins respectively.
	
	<note>
	 <para>
	  Neither sequential scans nor nested-loop joins can be disabled completely;
	  the <literal>-fs</literal> and <literal>-fn</literal>
	  options simply discourage the optimizer from using those
	  plan types if it has any other alternative.
	 </para>
	</note>
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>-i</term>
      <listitem>
       <para>
	Prevents query execution, but shows the plan tree.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>-L</term>
      <listitem>
       <para>
	Turns off the locking system.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>-O</term>
      <listitem>
       <para>
	Allows the structure of system tables to be modified.  This is
	used by <application>initdb</application>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>-p <replaceable class="parameter">database</replaceable></term>
      <listitem>
       <para>
	Indicates that this server has been started by a
	<application>postmaster</application> and makes different
	assumptions about buffer pool management, file descriptors,
	etc.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>-t pa[rser] | pl[anner] | e[xecutor]</term>
      <listitem>
       <para>
	Print timing statistics for each query relating to each of the
	major system modules.  This option cannot be used together
	with the <option>-s</option> option.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>-v <replaceable class="parameter">protocol</replaceable></term>
      <listitem>
       <para>
	Specifies the version number of the frontend/backend protocol
	to be used for this particular session.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>-W <replaceable class="parameter">seconds</replaceable></term>
      <listitem>
       <para>
	As soon as this option is encountered, the process sleeps for
	the specified amount of seconds.  This gives developers time
	to attach a debugger to the backend process.
       </para>
      </listitem>
     </varlistentry>

    </variablelist>
   </refsect3>
  </refsect2>
 </refsect1>

 <refsect1>
  <title>See also</title>

  <para>
   <xref linkend="app-initdb" endterm="app-initdb-title">,
   <xref linkend="app-ipcclean" endterm="app-ipcclean-title">,
   <xref linkend="app-postmaster" endterm="app-postmaster-title">
  </para>
 </refsect1>

</refentry>

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