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Thomas G. Lockhart
1998-09-16 14:43:12 +00:00
parent 5a68fd56cd
commit d2a907c6ad
18 changed files with 986 additions and 884 deletions
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164
doc/src/sgml/ref/create_rule.sgml
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@@ -14,35 +14,28 @@
</REFPURPOSE>
<REFSYNOPSISDIV>
<REFSYNOPSISDIVINFO>
<DATE>1998-04-15</DATE>
<DATE>1998-09-11</DATE>
</REFSYNOPSISDIVINFO>
<SYNOPSIS>
CREATE RULE <replaceable class="parameter">name</replaceable>
AS ON <replaceable class="parameter">event</replaceable>
TO <replaceable class="parameter">object</replaceable> [WHERE <replaceable class="parameter">condition</replaceable>]
DO [INSTEAD]
[<replaceable class="parameter">action</replaceable> | NOTHING ]
CREATE RULE <replaceable class="parameter">name</replaceable>
AS ON <replaceable class="parameter">event</replaceable>
TO <replaceable class="parameter">object</replaceable> [ WHERE <replaceable class="parameter">condition</replaceable> ]
DO [ INSTEAD ] [ <replaceable class="parameter">action</replaceable> | NOTHING ]
</SYNOPSIS>
<REFSECT2 ID="R2-SQL-CREATERULE-1">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
<DATE>1998-09-11</DATE>
</REFSECT2INFO>
<TITLE>
Inputs
</TITLE>
<PARA>
</PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
</TERM>
<LISTITEM>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">name</replaceable></ReturnValue>
<replaceable class="parameter">name</replaceable>
</TERM>
<LISTITEM>
<PARA>
@@ -52,31 +45,34 @@
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">event</replaceable></ReturnValue>
<replaceable class="parameter">event</replaceable>
</TERM>
<LISTITEM>
<PARA>
Event is one of <literal>select</literal>, <literal>update</literal>, <literal>delete</literal> or <literal>insert</literal>.
Event is one of <literal>select</literal>,
<literal>update</literal>, <literal>delete</literal>
or <literal>insert</literal>.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">object</replaceable></ReturnValue>
<replaceable class="parameter">object</replaceable>
</TERM>
<LISTITEM>
<PARA>
Object is either <replaceable class="parameter">table</replaceable> or <replaceable class="parameter">table</replaceable>.<replaceable class="parameter">column</replaceable>.
Object is either <replaceable class="parameter">table</replaceable>
or <replaceable class="parameter">table</replaceable>.<replaceable class="parameter">column</replaceable>.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">condition</replaceable></ReturnValue>
<replaceable class="parameter">condition</replaceable>
</TERM>
<LISTITEM>
<PARA>
Any SQL <literal>where</literal> clause. <literal>new</literal> or
Any SQL WHERE clause. <literal>new</literal> or
<literal>current</literal> can appear instead of an instance
variable whenever an instance variable is permissible in SQL.
</PARA>
@@ -84,25 +80,23 @@
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<ReturnValue><replaceable class="parameter">action</replaceable></ReturnValue>
<replaceable class="parameter">action</replaceable>
</TERM>
<LISTITEM>
<PARA>
Any SQL-statement. <literal>new</literal> or
Any SQL statement. <literal>new</literal> or
<literal>current</literal> can appear instead of an instance
variable whenever an instance variable is permissible in SQL.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</REFSECT2>
<REFSECT2 ID="R2-SQL-CREATERULE-2">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
<DATE>1998-09-11</DATE>
</REFSECT2INFO>
<TITLE>
Outputs
@@ -112,6 +106,7 @@
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<replaceable>status</replaceable>
</TERM>
<LISTITEM>
<PARA>
@@ -136,7 +131,7 @@
<REFSECT1 ID="R1-SQL-CREATERULE-1">
<REFSECT1INFO>
<DATE>1998-04-15</DATE>
<DATE>1998-09-11</DATE>
</REFSECT1INFO>
<TITLE>
Description
@@ -146,13 +141,13 @@
accessed, updated, inserted or deleted, there is a current instance (for
retrieves, updates and deletes) and a new instance (for updates and
appends). If the <replaceable class="parameter">event</replaceable>
specified in the <literal>on</literal> clause and the
specified in the ON clause and the
<replaceable class="parameter">condition</replaceable> specified in the
<literal>where</literal> clause are true for the current instance, the
WHERE clause are true for the current instance, the
<replaceable class="parameter">action</replaceable> part of the rule is
executed. First, however, values from fields in the current instance
and/or the new instance are substituted for
<literal> current.</literal><replaceable class="parameter">attribute-name</replaceable>
<literal>current.</literal><replaceable class="parameter">attribute-name</replaceable>
and <literal>new.</literal><replaceable class="parameter">attribute-name</replaceable>.
</para>
<para>
@@ -163,13 +158,13 @@
<REFSECT2 ID="R2-SQL-CREATERULE-3">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
<DATE>1998-09-11</DATE>
</REFSECT2INFO>
<TITLE>
Notes
</TITLE>
<para>
A note of caution about SQL rules is in order. If the same class name
A caution about SQL rules is in order. If the same class name
or instance variable appears in the
<replaceable class="parameter">event</replaceable>, the
<replaceable class="parameter">condition</replaceable> and the
@@ -179,13 +174,14 @@
variables that are shared between these clauses. For example, the following
two rules have the same semantics:
<programlisting>
on update to EMP.salary where EMP.name = "Joe"
do update EMP ( ... ) where ...
on update to EMP.salary where EMP.name = "Joe"
do update EMP ( ... ) where ...
on update to EMP-1.salary where EMP-2.name = "Joe"
do update EMP-3 ( ... ) where ...
on update to EMP-1.salary where EMP-2.name = "Joe"
do update EMP-3 ( ... ) where ...
</programlisting>
Each rule can have the optional tag <literal>instead</literal>. Without
Each rule can have the optional tag INSTEAD.
Without
this tag, <replaceable class="parameter">action</replaceable> will be
performed in addition to the user command when the
<replaceable class="parameter">event</replaceable> in the
@@ -194,7 +190,7 @@
<replaceable class="parameter">action</replaceable> part will be done
instead of the user command. In this later case, the
<replaceable class="parameter">action</replaceable> can be the keyword
<literal>nothing</literal>.
NOTHING.
</para>
<para>
When choosing between the rewrite and instance rule systems for a
@@ -205,32 +201,33 @@
<para>
It is very important to note that the rewrite rule system
will neither detect nor process circular rules. For example, though each
of the following two rule definitions are accepted by Postgres, the
retrieve command will cause Postgres to crash:
of the following two rule definitions are accepted by
<productname>Postgres</productname>, the
retrieve command will cause <productname>Postgres</productname> to crash:
<example>
<title>Example of a circular rewrite rule combination.</title>
<programlisting>
create rule bad_rule_combination_1 is
on select to EMP
do instead select to TOYEMP
create rule bad_rule_combination_1 is
on select to EMP
do instead select to TOYEMP
create rule bad_rule_combination_2 is
on select to TOYEMP
do instead select to EMP
create rule bad_rule_combination_2 is
on select to TOYEMP
do instead select to EMP
</programlisting>
<para>
This attempt to retrieve from EMP will cause Postgres to crash.
This attempt to retrieve from EMP will cause
<productname>Postgres</productname> to crash.
<programlisting>
select * from EMP
select * from EMP
</programlisting></para>
</example>
</para>
<para>
You must have rule definition access to a class in order
to define a rule on it (see change acl(l)).
<comment>
There is no manpage change or change_acl. What is intended?
</comment>
to define a rule on it. Use <command>GRANT</command>
and <command>REVOKE</command> to change permissions.
</PARA>
</REFSECT2>
</refsect1>
@@ -240,13 +237,13 @@
Usage
</TITLE>
<PARA>
Make Sam get the same salary adjustment as Joe
Make Sam get the same salary adjustment as Joe:
<programlisting>
create rule example_1 is
on update EMP.salary where current.name = "Joe"
do update EMP (salary = new.salary)
where EMP.name = "Sam"
create rule example_1 is
on update EMP.salary where current.name = "Joe"
do update EMP (salary = new.salary)
where EMP.name = "Sam"
</programlisting>
At the time Joe receives a salary adjustment, the event
@@ -257,44 +254,45 @@
Joe's salary on to Sam.
</para>
<para>
Make Bill get Joe's salary when it is accessed
Make Bill get Joe's salary when it is accessed:
<programlisting>
create rule example_2 is
on select to EMP.salary
where current.name = "Bill"
do instead
select (EMP.salary) from EMP where EMP.name = "Joe"
create rule example_2 is
on select to EMP.salary
where current.name = "Bill"
do instead
select (EMP.salary) from EMP
where EMP.name = "Joe"
</programlisting>
</para>
<para>
Deny Joe access to the salary of employees in the shoe
department. (<function>pg_username()</function> returns the name of
the current user)
department (<function>current_user</function> returns the name of
the current user):
<programlisting>
create rule example_3 is
on select to EMP.salary
where current.dept = "shoe" and pg_username() = "Joe"
do instead nothing
create rule example_3 is
on select to EMP.salary
where current.dept = "shoe" and current_user = "Joe"
do instead nothing
</programlisting>
</para>
<para>
Create a view of the employees working in the toy department.
<programlisting>
create TOYEMP(name = char16, salary = int4)
create TOYEMP(name = char16, salary = int4)
create rule example_4 is
on select to TOYEMP
do instead select (EMP.name, EMP.salary) from EMP
where EMP.dept = "toy"
create rule example_4 is
on select to TOYEMP
do instead
select (EMP.name, EMP.salary) from EMP
where EMP.dept = "toy"
</programlisting>
</para>
<para>
All new employees must make 5,000 or less
<programlisting>
create rule example_5 is
on insert to EMP where new.salary > 5000
do update newset salary = 5000
create rule example_5 is
on insert to EMP where new.salary > 5000
do update newset salary = 5000
</programlisting>
</PARA>
</REFSECT1>
@@ -303,9 +301,6 @@
<TITLE>
Bugs
</TITLE>
<PARA>
<literal>instead</literal> rules do not work properly.
</para>
<para>
The object in a SQL rule cannot be an array reference and
cannot have parameters.
@@ -328,18 +323,19 @@
Compatibility
</TITLE>
<PARA>
CREATE RULE statement is a PostgreSQL language extension.
CREATE RULE statement is a <productname>Postgres</productname>
language extension.
</PARA>
<REFSECT2 ID="R2-SQL-CREATERULE-4">
<REFSECT2INFO>
<DATE>1998-04-15</DATE>
<DATE>1998-09-11</DATE>
</REFSECT2INFO>
<TITLE>
SQL92
</TITLE>
<para>
There is no CREATE RULE statement in SQL92.
There is no CREATE RULE statement in <acronym>SQL92</acronym>.
</para>
</refsect2>
</refsect1>