Allow named parameters to be specified using => in addition to :=

SQL has standardized on => as the use of to specify named parameters,
and we've wanted for many years to support the same syntax ourselves,
but this has been complicated by the possible use of => as an operator
name.  In PostgreSQL 9.0, we began emitting a warning when an operator
named => was defined, and in PostgreSQL 9.2, we stopped shipping a
=>(text, text) operator as part of hstore.  By the time the next major
version of PostgreSQL is released, => will have been deprecated for a
full five years, so hopefully there won't be too many people still
relying on it.  We continue to support := for compatibility with
previous PostgreSQL releases.

Pavel Stehule, reviewed by Petr Jelinek, with a few documentation
tweaks by me.

3 files changed, 20 insertions, 9 deletions

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index da2ed673a7e..c198beaf396 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -6785,7 +6785,7 @@ SELECT SUBSTRING('XY1234Z', 'Y*?([0-9]{1,3})');
          Create interval from years, months, weeks, days, hours, minutes and
          seconds fields
         </entry>
-        <entry><literal>make_interval(days := 10)</literal></entry>
+        <entry><literal>make_interval(days => 10)</literal></entry>
         <entry><literal>10 days</literal></entry>
        </row>
 
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 4b81b088823..8283e252582 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -2596,10 +2596,10 @@ SELECT concat_lower_or_upper('Hello', 'World');
 
     <para>
      In named notation, each argument's name is specified using
-     <literal>:=</literal> to separate it from the argument expression.
+     <literal>=></literal> to separate it from the argument expression.
      For example:
 <screen>
-SELECT concat_lower_or_upper(a := 'Hello', b := 'World');
+SELECT concat_lower_or_upper(a => 'Hello', b => 'World');
  concat_lower_or_upper 
 -----------------------
  hello world
@@ -2610,13 +2610,24 @@ SELECT concat_lower_or_upper(a := 'Hello', b := 'World');
      using named notation is that the arguments may be specified in any
      order, for example:
 <screen>
-SELECT concat_lower_or_upper(a := 'Hello', b := 'World', uppercase := true);
+SELECT concat_lower_or_upper(a => 'Hello', b => 'World', uppercase => true);
  concat_lower_or_upper 
 -----------------------
  HELLO WORLD
 (1 row)
 
-SELECT concat_lower_or_upper(a := 'Hello', uppercase := true, b := 'World');
+SELECT concat_lower_or_upper(a => 'Hello', uppercase => true, b => 'World');
+ concat_lower_or_upper 
+-----------------------
+ HELLO WORLD
+(1 row)
+</screen>
+    </para>
+
+    <para>
+      An older syntax based on ":=" is supported for backward compatibility:
+<screen>
+    SELECT concat_lower_or_upper(a := 'Hello', uppercase := true, b := 'World');
  concat_lower_or_upper 
 -----------------------
  HELLO WORLD
@@ -2638,7 +2649,7 @@ SELECT concat_lower_or_upper(a := 'Hello', uppercase := true, b := 'World');
     already mentioned, named arguments cannot precede positional arguments.
     For example:
 <screen>
-SELECT concat_lower_or_upper('Hello', 'World', uppercase := true);
+SELECT concat_lower_or_upper('Hello', 'World', uppercase => true);
  concat_lower_or_upper 
 -----------------------
  HELLO WORLD
diff --git a/doc/src/sgml/xfunc.sgml b/doc/src/sgml/xfunc.sgml
index b85f2adc453..9de7ccc2582 100644
--- a/doc/src/sgml/xfunc.sgml
+++ b/doc/src/sgml/xfunc.sgml
@@ -776,14 +776,14 @@ SELECT mleast(VARIADIC ARRAY[]::numeric[]);
      <literal>VARIADIC</>.  For example, this will work:
 
 <screen>
-SELECT mleast(VARIADIC arr := ARRAY[10, -1, 5, 4.4]);
+SELECT mleast(VARIADIC arr => ARRAY[10, -1, 5, 4.4]);
 </screen>
 
      but not these:
 
 <screen>
-SELECT mleast(arr := 10);
-SELECT mleast(arr := ARRAY[10, -1, 5, 4.4]);
+SELECT mleast(arr => 10);
+SELECT mleast(arr => ARRAY[10, -1, 5, 4.4]);
 </screen>
     </para>
    </sect2>