Department of second thoughts: make checks for replacing a view slightly

more flexible, and improve the error reporting.  Also, add documentation
for REPLACE RULE/VIEW.

doc/src/sgml/ref/create_rule.sgml

@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_rule.sgml,v 1.36 2002/05/18 15:44:47 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_rule.sgml,v 1.37 2002/09/02 20:04:39 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -21,17 +21,15 @@ PostgreSQL documentation
    <date>2001-01-05</date>
   </refsynopsisdivinfo>
   <synopsis>
-CREATE RULE <replaceable class="parameter">name</replaceable> AS ON <replaceable class="parameter">event</replaceable>
+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 ] <replaceable class="parameter">action</replaceable>
 
 where <replaceable class="PARAMETER">action</replaceable> can be:
 
 NOTHING
-|
-<replaceable class="parameter">query</replaceable>
-|
-( <replaceable class="parameter">query</replaceable> ; <replaceable class="parameter">query</replaceable> ... )
+| <replaceable class="parameter">query</replaceable>
+| ( <replaceable class="parameter">query</replaceable> ; <replaceable class="parameter">query</replaceable> ... )
   </synopsis>
 
   <refsect2 id="R2-SQL-CREATERULE-1">
@@ -76,9 +74,10 @@ NOTHING
       <term><replaceable class="parameter">condition</replaceable></term>
       <listitem>
        <para>
-	Any SQL conditional expression (returning <type>boolean</type>).  The condition expression may not
+	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>.
+	<literal>old</literal>, and may not contain aggregate functions.
        </para>
       </listitem>
      </varlistentry>
@@ -142,6 +141,14 @@ CREATE RULE
    Description
   </title>
 
+  <para>
+   <command>CREATE RULE</command> defines a new rule applying to a specified
+   table or view.
+   <command>CREATE OR REPLACE RULE</command> will either create a
+   new rule, or replace an existing rule of the same name for the same
+   table.
+  </para>
+
   <para>
    The <productname>PostgreSQL</productname> 
    <firstterm>rule system</firstterm> allows one to define an
@@ -318,7 +325,7 @@ UPDATE mytable SET name = 'foo' WHERE id = 42;
    </title>
 
    <para>
-    <command>CREATE RULE</command> statement is a <productname>PostgreSQL</productname>
+    <command>CREATE RULE</command> is a <productname>PostgreSQL</productname>
     language extension.
     There is no <command>CREATE RULE</command> statement in <acronym>SQL92</acronym>.
    </para>

doc/src/sgml/ref/create_view.sgml

@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_view.sgml,v 1.18 2002/05/18 15:44:47 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_view.sgml,v 1.19 2002/09/02 20:04:39 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -21,7 +21,7 @@ PostgreSQL documentation
    <date>2000-03-25</date>
   </refsynopsisdivinfo>
   <synopsis>
-CREATE VIEW <replaceable class="PARAMETER">view</replaceable> [ ( <replaceable
+CREATE [ OR REPLACE ] VIEW <replaceable class="PARAMETER">view</replaceable> [ ( <replaceable
 class="PARAMETER">column name list</replaceable> ) ] AS SELECT <replaceable class="PARAMETER">query</replaceable>
   </synopsis>
 
@@ -132,13 +132,21 @@ CREATE VIEW vista AS SELECT text 'Hello World'
   <title>
    Description
   </title>
+
   <para>
-   <command>CREATE VIEW</command> will define a view of a query.
+   <command>CREATE VIEW</command> defines a view of a query.
    The view is not physically materialized. Instead, a query
    rewrite rule (an <literal>ON SELECT</> rule) is automatically generated to
    support SELECT operations on views.
   </para>
 
+  <para>
+   <command>CREATE OR REPLACE VIEW</command> is similar, but if a view
+   of the same name already exists, it is replaced.  You can only replace
+   a view with a new query that generates the identical set of columns
+   (i.e., same column names and data types).
+  </para>
+
   <para>
    If a schema name is given (for example, <literal>CREATE VIEW
    myschema.myview ...</>) then the view is created in the
@@ -206,6 +214,7 @@ SELECT * FROM kinds;
    <title>
     SQL92
    </title>
+
    <para>
     SQL92 specifies some additional capabilities for the
     <command>CREATE VIEW</command> statement:
@@ -253,6 +262,12 @@ CREATE VIEW <replaceable class="parameter">view</replaceable> [ <replaceable cla
      </varlistentry>
     </variablelist>
    </para>
+
+   <para>
+    <command>CREATE OR REPLACE VIEW</command> is a
+    <productname>PostgreSQL</productname> language extension.
+   </para>
+
   </refsect2>
  </refsect1>
 </refentry>

doc/src/sgml/release.sgml

@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/release.sgml,v 1.156 2002/08/30 22:18:05 tgl Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/release.sgml,v 1.157 2002/09/02 20:04:39 tgl Exp $
 -->
 
 <appendix id="release">
@@ -24,6 +24,7 @@ CDATA means the content is "SGML-free", so you can write without
 worries about funny characters.
 -->
 <literallayout><![CDATA[
+CREATE OR REPLACE VIEW, CREATE OR REPLACE RULE are available
 No-autocommit mode is available (set autocommit to off)
 Substantial improvements in functionality for functions returning sets
 Client libraries older than 6.3 no longer supported (version 0 protocol removed)