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196 lines
4.2 KiB
Plaintext
196 lines
4.2 KiB
Plaintext
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/unlisten.sgml,v 1.14 2001/01/13 23:58:55 petere Exp $
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Postgres documentation
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-->
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<refentry id="SQL-UNLISTEN">
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<refmeta>
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<refentrytitle>
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UNLISTEN
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</refentrytitle>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>
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UNLISTEN
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</refname>
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<refpurpose>
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Stop listening for notification
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</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<refsynopsisdivinfo>
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<date>1998-10-19</date>
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</refsynopsisdivinfo>
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<synopsis>
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UNLISTEN { <replaceable class="PARAMETER">notifyname</replaceable> | * }
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</synopsis>
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<refsect2 id="R2-SQL-UNLISTEN-1">
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<refsect2info>
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<date>1998-10-19</date>
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</refsect2info>
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<title>
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Inputs
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</title>
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<para>
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<variablelist>
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<varlistentry>
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<term><replaceable class="PARAMETER">notifyname</replaceable></term>
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<listitem>
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<para>
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Name of previously registered notify condition.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>*</literal></term>
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<listitem>
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<para>
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All current listen registrations for this backend are cleared.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect2>
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<refsect2 id="R2-SQL-UNLISTEN-2">
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<refsect2info>
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<date>1998-10-19</date>
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</refsect2info>
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<title>
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Outputs
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</title>
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<para>
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<variablelist>
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<varlistentry>
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<term><computeroutput>
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<returnvalue>UNLISTEN</returnvalue>
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</computeroutput></term>
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<listitem>
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<para>
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Acknowledgment that statement has executed.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect2>
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</refsynopsisdiv>
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<refsect1 id="R1-SQL-UNLISTEN-1">
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<refsect1info>
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<date>1998-10-19</date>
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</refsect1info>
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<title>
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Description
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</title>
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<para>
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<command>UNLISTEN</command>
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is used to remove an existing <command>NOTIFY</command> registration.
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UNLISTEN cancels any existing registration of the current
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<productname>Postgres</productname> session as a listener on the notify
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condition <replaceable class="PARAMETER">notifyname</replaceable>.
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The special condition wildcard "*" cancels all listener registrations
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for the current session.
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</para>
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<para>
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<xref endterm="sql-notify-title" linkend="sql-notify">
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contains a more extensive
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discussion of the use of <command>LISTEN</command> and
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<command>NOTIFY</command>.
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</para>
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<refsect2 id="R2-SQL-UNLISTEN-3">
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<refsect2info>
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<date>1998-10-19</date>
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</refsect2info>
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<title>
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Notes
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</title>
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<para>
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<replaceable class="PARAMETER">notifyname</replaceable>
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need not be a valid class name but can be any string valid
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as a name up to 32 characters long.
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</para>
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<para>
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The backend does not complain if you UNLISTEN something you were not
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listening for.
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Each backend will automatically execute <command>UNLISTEN *</command> when
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exiting.
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</para>
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</refsect2>
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</refsect1>
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<refsect1 id="R1-SQL-UNLISTEN-2">
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<title>
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Usage
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</title>
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<para>
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To subscribe to an existing registration:
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<programlisting>
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LISTEN virtual;
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LISTEN
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NOTIFY virtual;
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NOTIFY
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Asynchronous NOTIFY 'virtual' from backend with pid '8448' received
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</programlisting>
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</para>
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<para>
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Once UNLISTEN has been executed, further NOTIFY commands will be
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ignored:
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<programlisting>
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UNLISTEN virtual;
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UNLISTEN
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NOTIFY virtual;
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NOTIFY
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-- notice no NOTIFY event is received
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</programlisting>
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</para>
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</refsect1>
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<refsect1 id="R1-SQL-UNLISTEN-3">
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<title>
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Compatibility
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</title>
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<refsect2 id="R2-SQL-UNLISTEN-4">
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<refsect2info>
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<date>1998-10-19</date>
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</refsect2info>
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<title>
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SQL92
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</title>
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<para>
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There is no <command>UNLISTEN</command> in <acronym>SQL92</acronym>.
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</para>
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</refsect2>
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</refsect1>
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</refentry>
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