Deprecate the use of => as an operator name.

In HEAD, emit a warning when an operator named => is defined.
In both HEAD and the backbranches (except in 8.2, where contrib
modules do not have documentation), document that hstore's text =>
text operator may be removed in a future release, and encourage the
use of the hstore(text, text) function instead.  This function only
exists in HEAD (previously, it was called tconvert), so backpatch
it back to 8.2, when hstore was added.  Per discussion.

doc/src/sgml/hstore.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/hstore.sgml,v 1.10 2010/06/18 03:52:03 rhaas Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/hstore.sgml,v 1.11 2010/06/22 11:36:16 rhaas Exp $ -->
 
 <sect1 id="hstore">
  <title>hstore</title>
@@ -225,6 +225,14 @@
    </para>
   </note>
 
+  <note>
+  <para>
+   The <literal>=&gt;</> operator is deprecated and may be removed in a
+   future release.  Use the <literal>hstore(text, text)</literal> function
+   instead.
+   </para>
+  </note>
+
   <table id="hstore-func-table">
    <title><type>hstore</> Functions</title>
 
@@ -265,6 +273,14 @@
       <entry><literal>"a"=&gt;"1","b"=&gt;"2"</literal></entry>
      </row>
 
+     <row>
+      <entry><function>hstore(text, text)</function></entry>
+      <entry><type>hstore</type></entry>
+      <entry>make single-item <type>hstore</></entry>
+      <entry><literal>hstore('a', 'b')</literal></entry>
+      <entry><literal>"a"=&gt;"b"</literal></entry>
+     </row>
+
      <row>
       <entry><function>akeys(hstore)</function></entry>
       <entry><type>text[]</type></entry>

doc/src/sgml/ref/create_operator.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_operator.sgml,v 1.52 2010/04/03 07:22:58 petere Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_operator.sgml,v 1.53 2010/06/22 11:36:16 rhaas Exp $
 PostgreSQL documentation
 -->
 
@@ -71,6 +71,12 @@ CREATE OPERATOR <replaceable>name</replaceable> (
      parse SQL-compliant commands without requiring spaces between tokens.
      </para>
     </listitem>
+    <listitem>
+     <para>
+     The use of <literal>=&gt;</> as an operator name is deprecated.  It may
+     be disallowed altogether in a future release.
+     </para>
+    </listitem>
    </itemizedlist>
   </para>
 

src/backend/commands/operatorcmds.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/operatorcmds.c,v 1.45 2010/02/14 18:42:14 rhaas Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/operatorcmds.c,v 1.46 2010/06/22 11:36:16 rhaas Exp $
  *
  * DESCRIPTION
  *	  The "DefineFoo" routines take the parse tree and pick out the
@@ -88,6 +88,16 @@ DefineOperator(List *names, List *parameters)
 	/* Convert list of names to a name and namespace */
 	oprNamespace = QualifiedNameGetCreationNamespace(names, &oprName);
 
+	/*
+	 * The SQL standard committee has decided that => should be used for
+	 * named parameters; therefore, a future release of PostgreSQL may
+	 * disallow it as the name of a user-defined operator.
+	 */
+	if (strcmp(oprName, "=>") == 0)
+		ereport(WARNING,
+				(errmsg("=> is deprecated as an operator name"),
+				 errdetail("This name may be disallowed altogether in future versions of PostgreSQL.")));
+
 	/* Check we have creation rights in target namespace */
 	aclresult = pg_namespace_aclcheck(oprNamespace, GetUserId(), ACL_CREATE);
 	if (aclresult != ACLCHECK_OK)