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Add documentation for the recent 'ALSO' patch for CREATE RULE. Along

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the way, fix a typo and make a few SGML cleanups.
This commit is contained in:
Neil Conway 2004-03-09 19:30:21 +00:00
parent f31a43f9ae
commit 47110ace3a
1 changed files with 40 additions and 24 deletions
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64
doc/src/sgml/ref/create_rule.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/create_rule.sgml,v 1.43 2004/03/04 14:32:12 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/create_rule.sgml,v 1.44 2004/03/09 19:30:21 neilc Exp $
PostgreSQL documentation
-->
@ -22,7 +22,7 @@ PostgreSQL documentation
<synopsis>
CREATE [ OR REPLACE ] RULE <replaceable class="parameter">name</replaceable> AS ON <replaceable class="parameter">event</replaceable>
TO <replaceable class="parameter">table</replaceable> [ WHERE <replaceable class="parameter">condition</replaceable> ]
DO [ INSTEAD ] { NOTHING | <replaceable class="parameter">command</replaceable> | ( <replaceable class="parameter">command</replaceable> ; <replaceable class="parameter">command</replaceable> ... ) }
DO [ ALSO | INSTEAD ] { NOTHING | <replaceable class="parameter">command</replaceable> | ( <replaceable class="parameter">command</replaceable> ; <replaceable class="parameter">command</replaceable> ... ) }
</synopsis>
</refsynopsisdiv>
@ -43,13 +43,13 @@ CREATE [ OR REPLACE ] RULE <replaceable class="parameter">name</replaceable> AS
or deletions in database tables. Roughly speaking, a rule causes
additional commands to be executed when a given command on a given
table is executed. Alternatively, an <literal>INSTEAD</literal>
rule can replace a given command by another, or cause a command
not to be executed at all. Rules are used to implement table
views as well. It is important to realize that a rule is really
a command transformation mechanism, or command macro. The
transformation happens before the execution of the commands starts.
If you actually want an operation that fires independently for each
physical row, you probably want to use a trigger, not a rule.
rule can replace a given command by another, or cause a command
not to be executed at all. Rules are used to implement table
views as well. It is important to realize that a rule is really
a command transformation mechanism, or command macro. The
transformation happens before the execution of the commands starts.
If you actually want an operation that fires independently for each
physical row, you probably want to use a trigger, not a rule.
More information about the rules system is in <xref linkend="rules">.
</para>
@ -111,7 +111,7 @@ CREATE [ OR REPLACE ] RULE <replaceable class="parameter">name</replaceable> AS
<term><replaceable class="parameter">event</replaceable></term>
<listitem>
<para>
The even is one of <literal>SELECT</literal>,
The event is one of <literal>SELECT</literal>,
<literal>INSERT</literal>, <literal>UPDATE</literal>, or
<literal>DELETE</literal>.
</para>
@ -132,10 +132,10 @@ CREATE [ OR REPLACE ] RULE <replaceable class="parameter">name</replaceable> AS
<term><replaceable class="parameter">condition</replaceable></term>
<listitem>
<para>
Any SQL conditional expression (returning <type>boolean</type>).
The condition expression may not refer to any tables except
<literal>NEW</literal> and <literal>OLD</literal>, and may not
contain aggregate functions.
Any <acronym>SQL</acronym> conditional expression (returning
<type>boolean</type>). The condition expression may not refer
to any tables except <literal>NEW</> and <literal>OLD</>, and
may not contain aggregate functions.
</para>
</listitem>
</varlistentry>
@ -145,8 +145,24 @@ CREATE [ OR REPLACE ] RULE <replaceable class="parameter">name</replaceable> AS
<listitem>
<para>
<literal>INSTEAD</literal> indicates that the commands should be
executed <emphasis>instead</> of the original command, not in
addition to the original command.
executed <emphasis>instead of</> the original command.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>ALSO</option></term>
<listitem>
<para>
<literal>ALSO</literal> indicates that the commands should be
executed <emphasis>in addition to</emphasis> the original
command.
</para>
<para>
If neither <literal>ALSO</literal> nor
<literal>INSTEAD</literal> is specified, <literal>ALSO</literal>
is the default.
</para>
</listitem>
</varlistentry>
@ -156,9 +172,9 @@ CREATE [ OR REPLACE ] RULE <replaceable class="parameter">name</replaceable> AS
<listitem>
<para>
The command or commands that make up the rule action. Valid
commands are <literal>SELECT</literal>,
<literal>INSERT</literal>, <literal>UPDATE</literal>,
<literal>DELETE</literal>, or <literal>NOTIFY</literal>.
commands are <command>SELECT</command>,
<command>INSERT</command>, <command>UPDATE</command>,
<command>DELETE</command>, or <command>NOTIFY</command>.
</para>
</listitem>
</varlistentry>
@ -215,14 +231,14 @@ SELECT * FROM t1;
issued even if there are not any rows that the rule should apply
to. For example, in
<programlisting>
CREATE RULE notify_me AS ON UPDATE TO mytable DO NOTIFY mytable;
CREATE RULE notify_me AS ON UPDATE TO mytable DO ALSO NOTIFY mytable;
UPDATE mytable SET name = 'foo' WHERE id = 42;
</programlisting>
one <command>NOTIFY</command> event will be sent during the
<command>UPDATE</command>, whether or not there are any rows with
<literal>id = 42</literal>. This is an implementation restriction
that may be fixed in future releases.
<command>UPDATE</command>, whether or not there are any rows that
match the condition <literal>id = 42</literal>. This is an
implementation restriction that may be fixed in future releases.
</para>
</refsect1>
@ -232,7 +248,7 @@ UPDATE mytable SET name = 'foo' WHERE id = 42;
<para>
<command>CREATE RULE</command> is a
<productname>PostgreSQL</productname> language extension, as is the
entire rules system.
entire query rewrite system.
</para>
</refsect1>
</refentry>