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, 16 insertions, 11 deletions

diff --git a/src/backend/commands/operatorcmds.c b/src/backend/commands/operatorcmds.c
index 1efaacfd5e2..b4a1aac3a14 100644
--- a/src/backend/commands/operatorcmds.c
+++ b/src/backend/commands/operatorcmds.c
@@ -87,16 +87,6 @@ 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)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 435c0451cae..21b8897038f 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -533,7 +533,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
  */
 %token <str>	IDENT FCONST SCONST BCONST XCONST Op
 %token <ival>	ICONST PARAM
-%token			TYPECAST DOT_DOT COLON_EQUALS
+%token			TYPECAST DOT_DOT COLON_EQUALS EQUALS_GREATER
 
 /*
  * If you want to make any keyword changes, update the keyword table in
@@ -12567,6 +12567,15 @@ func_arg_expr:  a_expr
 					na->location = @1;
 					$$ = (Node *) na;
 				}
+			| param_name EQUALS_GREATER a_expr
+				{
+					NamedArgExpr *na = makeNode(NamedArgExpr);
+					na->name = $1;
+					na->arg = (Expr *) $3;
+					na->argnumber = -1;		/* until determined */
+					na->location = @1;
+					$$ = (Node *) na;
+				}
 		;
 
 type_list:	Typename								{ $$ = list_make1($1); }
diff --git a/src/backend/parser/scan.l b/src/backend/parser/scan.l
index a78ce03fbd5..a0e20434ef3 100644
--- a/src/backend/parser/scan.l
+++ b/src/backend/parser/scan.l
@@ -334,6 +334,7 @@ identifier		{ident_start}{ident_cont}*
 typecast		"::"
 dot_dot			\.\.
 colon_equals	":="
+equals_greater	"=>"
 
 /*
  * "self" is the set of chars that should be returned as single-character
@@ -808,6 +809,11 @@ other			.
 					return COLON_EQUALS;
 				}
 
+{equals_greater}	{
+					SET_YYLLOC();
+					return EQUALS_GREATER;
+				}
+
 {self}			{
 					SET_YYLLOC();
 					return yytext[0];