show.sgml

postgresql8.3.4源码,开源数据库

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$PostgreSQL: pgsql/doc/src/sgml/ref/show.sgml,v 1.45 2008/01/03 21:23:15 tgl Exp $
PostgreSQL documentation
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<refentry id="SQL-SHOW">
 <refmeta>
  <refentrytitle id="SQL-SHOW-TITLE">SHOW</refentrytitle>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>SHOW</refname>
  <refpurpose>show the value of a run-time parameter</refpurpose>
 </refnamediv>

 <indexterm zone="sql-show">
  <primary>SHOW</primary>
 </indexterm>

 <refsynopsisdiv>
<synopsis>
SHOW <replaceable class="PARAMETER">name</replaceable>
SHOW ALL
</synopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

  <para>
   <command>SHOW</command> will display the current setting of
   run-time parameters. These variables can be set using the
   <command>SET</command> statement, by editing the
   <filename>postgresql.conf</filename> configuration file, through
   the <envar>PGOPTIONS</envar> environmental variable (when using
   <application>libpq</> or a <application>libpq</>-based
   application), or through command-line flags when starting the
   <command>postgres</command> server.  See <xref
   linkend="runtime-config"> for details.
  </para>
 </refsect1>

 <refsect1>
  <title>Parameters</title>

  <variablelist>
   <varlistentry>
    <term><replaceable class="PARAMETER">name</replaceable></term>
    <listitem>
     <para>
      The name of a run-time parameter.  Available parameters are
      documented in <xref linkend="runtime-config"> and on the <xref
      linkend="SQL-SET" endterm="SQL-SET-title"> reference page.  In
      addition, there are a few parameters that can be shown but not
      set:

      <variablelist>
       <varlistentry>
        <term><literal>SERVER_VERSION</literal></term>
        <listitem>
         <para>
          Shows the server's version number.
         </para>
        </listitem>
       </varlistentry>

       <varlistentry>
        <term><literal>SERVER_ENCODING</literal></term>
        <listitem>
         <para>
          Shows the server-side character set encoding.  At present,
          this parameter can be shown but not set, because the
          encoding is determined at database creation time.
         </para>
        </listitem>
       </varlistentry>

       <varlistentry>
        <term><literal>LC_COLLATE</literal></term>
        <listitem>
         <para>
          Shows the database's locale setting for collation (text
          ordering).  At present, this parameter can be shown but not
          set, because the setting is determined at
          <command>initdb</> time.
         </para>
        </listitem>
       </varlistentry>

       <varlistentry>
        <term><literal>LC_CTYPE</literal></term>
        <listitem>
         <para>
          Shows the database's locale setting for character
          classification.  At present, this parameter can be shown but
          not set, because the setting is determined at
          <command>initdb</> time.
         </para>
        </listitem>
       </varlistentry>

       <varlistentry>
        <term><literal>IS_SUPERUSER</literal></term>
        <listitem>
         <para>
          True if the current role has superuser privileges.
         </para>
        </listitem>
       </varlistentry>
      </variablelist>
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>ALL</literal></term>
    <listitem>
     <para>
      Show the values of all configuration parameters, with descriptions.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

 <refsect1>
  <title>Notes</title>

  <para>
   The function <function>current_setting</function> produces
   equivalent output; see <xref linkend="functions-admin">.
   Also, the
   <link linkend="view-pg-settings"><structname>pg_settings</structname></link>
   system view produces the same information.

  </para>
 </refsect1>

 <refsect1>
  <title>Examples</title>

  <para>
   Show the current setting of the parameter <varname>DateStyle</varname>:

<programlisting>
SHOW DateStyle;
 DateStyle
-----------
 ISO, MDY
(1 row)
</programlisting>
  </para>

  <para>
   Show the current setting of the parameter <varname>geqo</varname>:
<programlisting>
SHOW geqo;
 geqo
------
 on
(1 row)
</programlisting>
  </para>

  <para>
   Show all settings:
<programlisting>
SHOW ALL;
              name              |            setting             |                                         description                                          
--------------------------------+--------------------------------+----------------------------------------------------------------------------------------------
 add_missing_from               | off                            | Automatically adds missing table references to FROM clauses.
 allow_system_table_mods        | off                            | Allows modifications of the structure of system tables.
    .
    .
    .
 work_mem                       | 1024                           | Sets the maximum memory to be used for query workspaces.
 zero_damaged_pages             | off                            | Continues processing past damaged page headers.
(146 rows)
</programlisting>
  </para>
 </refsect1>

 <refsect1>
  <title>Compatibility</title>

  <para>
   The <command>SHOW</command> command is a
   <productname>PostgreSQL</productname> extension.
  </para>
 </refsect1>

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

  <simplelist type="inline">
   <member><xref linkend="SQL-SET" endterm="SQL-SET-title"></member>
   <member><xref linkend="SQL-RESET" endterm="SQL-RESET-title"></member>
  </simplelist>
 </refsect1>

</refentry>