Allow => syntax for named cursor arguments in plpgsql.

We've traditionally accepted "name := value" syntax for
cursor arguments in plpgsql.  But it turns out that the
equivalent statements in Oracle use "name => value".
Since we accept both forms of punctuation for function
arguments, it makes sense to do the same here.

Author: Pavel Stehule <pavel.stehule@gmail.com>
Reviewed-by: Gilles Darold <gilles@darold.net>
Discussion: https://postgr.es/m/CAFj8pRA3d0ARQEMbABa1n6q25AUdNmyO8aGs56XNf9pD4sRMjQ@mail.gmail.com

doc/src/sgml/plpgsql.sgml

@@ -3317,7 +3317,7 @@ OPEN curs1 FOR EXECUTE format('SELECT * FROM %I WHERE col1 = $1',tabname) USING
      <title>Opening a Bound Cursor</title>
 
 <synopsis>
-OPEN <replaceable>bound_cursorvar</replaceable> <optional> ( <optional> <replaceable>argument_name</replaceable> := </optional> <replaceable>argument_value</replaceable> <optional>, ...</optional> ) </optional>;
+OPEN <replaceable>bound_cursorvar</replaceable> <optional> ( <optional> <replaceable>argument_name</replaceable> { := | =&gt; } </optional> <replaceable>argument_value</replaceable> <optional>, ...</optional> ) </optional>;
 </synopsis>
 
          <para>
@@ -3340,7 +3340,8 @@ OPEN <replaceable>bound_cursorvar</replaceable> <optional> ( <optional> <replace
           Argument values can be passed using either <firstterm>positional</firstterm>
           or <firstterm>named</firstterm> notation.  In positional
           notation, all arguments are specified in order.  In named notation,
-          each argument's name is specified using <literal>:=</literal> to
+          each argument's name is specified using <literal>:=</literal>
+          or <literal>=&gt;</literal> to
           separate it from the argument expression. Similar to calling
           functions, described in <xref linkend="sql-syntax-calling-funcs"/>, it
           is also allowed to mix positional and named notation.
@@ -3352,6 +3353,7 @@ OPEN <replaceable>bound_cursorvar</replaceable> <optional> ( <optional> <replace
 OPEN curs2;
 OPEN curs3(42);
 OPEN curs3(key := 42);
+OPEN curs3(key =&gt; 42);
 </programlisting>
          </para>
 
@@ -3672,7 +3674,7 @@ COMMIT;
 
 <synopsis>
 <optional> &lt;&lt;<replaceable>label</replaceable>&gt;&gt; </optional>
-FOR <replaceable>recordvar</replaceable> IN <replaceable>bound_cursorvar</replaceable> <optional> ( <optional> <replaceable>argument_name</replaceable> := </optional> <replaceable>argument_value</replaceable> <optional>, ...</optional> ) </optional> LOOP
+FOR <replaceable>recordvar</replaceable> IN <replaceable>bound_cursorvar</replaceable> <optional> ( <optional> <replaceable>argument_name</replaceable> { := | =&gt; } </optional> <replaceable>argument_value</replaceable> <optional>, ...</optional> ) </optional> LOOP
     <replaceable>statements</replaceable>
 END LOOP <optional> <replaceable>label</replaceable> </optional>;
 </synopsis>

src/pl/plpgsql/src/pl_gram.y

@@ -3955,9 +3955,12 @@ read_cursor_args(PLpgSQL_var *cursor, int until, YYSTYPE *yylvalp, YYLTYPE *yyll
 					tok2;
 		int			arglocation;
 
-		/* Check if it's a named parameter: "param := value" */
+		/*
+		 * Check if it's a named parameter: "param := value"
+		 * or "param => value"
+		 */
 		plpgsql_peek2(&tok1, &tok2, &arglocation, NULL, yyscanner);
-		if (tok1 == IDENT && tok2 == COLON_EQUALS)
+		if (tok1 == IDENT && (tok2 == COLON_EQUALS || tok2 == EQUALS_GREATER))
 		{
 			char	   *argname;
 			IdentifierLookup save_IdentifierLookup;
@@ -3983,11 +3986,11 @@ read_cursor_args(PLpgSQL_var *cursor, int until, YYSTYPE *yylvalp, YYLTYPE *yyll
 						 parser_errposition(*yyllocp)));
 
 			/*
-			 * Eat the ":=". We already peeked, so the error should never
+			 * Eat the ":=" or "=>".  We already peeked, so the error should
-			 * happen.
+			 * never happen.
 			 */
 			tok2 = yylex(yylvalp, yyllocp, yyscanner);
-			if (tok2 != COLON_EQUALS)
+			if (tok2 != COLON_EQUALS && tok2 != EQUALS_GREATER)
 				yyerror(yyllocp, NULL, yyscanner, "syntax error");
 
 			any_named = true;

src/test/regress/expected/plpgsql.out

@@ -2419,7 +2419,8 @@ declare
   p2 int4 := 1006;
   n int4;
 begin
-  open c1 (p1 := p1, p2 := p2, debug := 2);
+  -- use both supported syntaxes for named arguments
+  open c1 (p1 := p1, p2 => p2, debug => 2);
   fetch c1 into n;
   return n;
 end $$ language plpgsql;
@@ -3487,7 +3488,8 @@ begin
     raise notice '% from %', r.i, c;
   end loop;
   -- again, to test if cursor was closed properly
-  for r in c(9,10) loop
+  -- (and while we're at it, test named-parameter notation)
+  for r in c(r2 := 10, r1 => 9) loop
     raise notice '% from %', r.i, c;
   end loop;
   -- and test a parameterless cursor

src/test/regress/sql/plpgsql.sql

@@ -2072,7 +2072,8 @@ declare
   p2 int4 := 1006;
   n int4;
 begin
-  open c1 (p1 := p1, p2 := p2, debug := 2);
+  -- use both supported syntaxes for named arguments
+  open c1 (p1 := p1, p2 => p2, debug => 2);
   fetch c1 into n;
   return n;
 end $$ language plpgsql;
@@ -2934,7 +2935,8 @@ begin
     raise notice '% from %', r.i, c;
   end loop;
   -- again, to test if cursor was closed properly
-  for r in c(9,10) loop
+  -- (and while we're at it, test named-parameter notation)
+  for r in c(r2 := 10, r1 => 9) loop
     raise notice '% from %', r.i, c;
   end loop;
   -- and test a parameterless cursor