doc/src/sgml/ref/unlisten.sgml

   1 <!--
   2 $PostgreSQL$
   3 PostgreSQL documentation
   4 -->
   5
   6 <refentry id="SQL-UNLISTEN">
   7  <refmeta>
   8   <refentrytitle id="SQL-UNLISTEN-TITLE">UNLISTEN</refentrytitle>
   9   <manvolnum>7</manvolnum>
  10   <refmiscinfo>SQL - Language Statements</refmiscinfo>
  11  </refmeta>
  12
  13  <refnamediv>
  14   <refname>UNLISTEN</refname>
  15   <refpurpose>stop listening for a notification</refpurpose>
  16  </refnamediv>
  17
  18  <indexterm zone="sql-unlisten">
  19   <primary>UNLISTEN</primary>
  20  </indexterm>
  21
  22  <refsynopsisdiv>
  23 <synopsis>
  24 UNLISTEN { <replaceable class="PARAMETER">name</replaceable> | * }
  25 </synopsis>
  26  </refsynopsisdiv>
  27
  28  <refsect1>
  29   <title>Description</title>
  30
  31   <para>
  32    <command>UNLISTEN</command> is used to remove an existing
  33    registration for <command>NOTIFY</command> events.
  34    <command>UNLISTEN</command> cancels any existing registration of
  35    the current <productname>PostgreSQL</productname> session as a
  36    listener on the notification <replaceable
  37    class="PARAMETER">name</replaceable>.  The special wildcard
  38    <literal>*</literal> cancels all listener registrations for the
  39    current session.
  40   </para>
  41
  42   <para>
  43    <xref endterm="sql-notify-title" linkend="sql-notify">
  44    contains a more extensive
  45    discussion of the use of <command>LISTEN</command> and
  46    <command>NOTIFY</command>.
  47   </para>
  48  </refsect1>
  49
  50  <refsect1>
  51   <title>Parameters</title>
  52
  53   <variablelist>
  54    <varlistentry>
  55     <term><replaceable class="PARAMETER">name</replaceable></term>
  56     <listitem>
  57      <para>
  58       Name of a notification (any identifier).
  59      </para>
  60     </listitem>
  61    </varlistentry>
  62
  63    <varlistentry>
  64     <term><literal>*</literal></term>
  65     <listitem>
  66      <para>
  67       All current listen registrations for this session are cleared.
  68      </para>
  69     </listitem>
  70    </varlistentry>
  71   </variablelist>
  72  </refsect1>
  73
  74  <refsect1>
  75   <title>Notes</title>
  76
  77   <para>
  78    You can unlisten something you were not listening for; no warning or error
  79    will appear.
  80   </para>
  81
  82   <para>
  83    At the end of each session, <command>UNLISTEN *</command> is
  84    automatically executed.
  85   </para>
  86  </refsect1>
  87
  88  <refsect1>
  89   <title>Examples</title>
  90
  91   <para>
  92    To make a registration:
  93
  94 <programlisting>
  95 LISTEN virtual;
  96 NOTIFY virtual;
  97 Asynchronous notification "virtual" received from server process with PID 8448.
  98 </programlisting>
  99   </para>
 100
 101   <para>
 102    Once <command>UNLISTEN</> has been executed, further <command>NOTIFY</>
 103    commands will be ignored:
 104
 105 <programlisting>
 106 UNLISTEN virtual;
 107 NOTIFY virtual;
 108 -- no NOTIFY event is received
 109 </programlisting>
 110   </para>
 111  </refsect1>
 112
 113  <refsect1>
 114   <title>Compatibility</title>
 115
 116   <para>
 117    There is no <command>UNLISTEN</command> command in the SQL standard.
 118   </para>
 119  </refsect1>
 120
 121  <refsect1>
 122   <title>See Also</title>
 123
 124   <simplelist type="inline">
 125    <member><xref linkend="sql-listen" endterm="sql-listen-title"></member>
 126    <member><xref linkend="sql-notify" endterm="sql-notify-title"></member>
 127   </simplelist>
 128  </refsect1>
 129 </refentry>