Error codes for LIMIT and OFFSET

I was looking into adding new specific SQL:2008 error codes for invalid
LIMIT and OFFSET values (see attached patch), when I came across an
existing error code definition:

#define ERRCODE_INVALID_LIMIT_VALUE  MAKE_SQLSTATE('2','2', '0','2','0')

This definition has been in our sources since error codes were first
added, but I don't find this code in the standard (it uses a
standard-space SQLSTATE code), and as far as I can tell, it hasn't been
actually used anywhere.  Except that PL/pgSQL defines it in plerrcodes.h
(and Google shows that various other interfaces list it as well), but it
can never happen, I think.

What should we do here, if anything?  Redefine
ERRCODE_INVALID_LIMIT_VALUE to the new SQL:2008 code?  Or remove the
whole thing (assuming that no PL/pgSQL code actually referes to it)?
Index: src/backend/executor/nodeLimit.c
===================================================================
RCS file: /cvsroot/pgsql/src/backend/executor/nodeLimit.c,v
retrieving revision 1.35
diff -u -3 -p -r1.35 nodeLimit.c
--- src/backend/executor/nodeLimit.c    1 Jan 2009 17:23:41 -0000    1.35
+++ src/backend/executor/nodeLimit.c    27 Feb 2009 11:23:13 -0000
@@ -247,7 +247,7 @@ recompute_limits(LimitState *node)
             node->offset = DatumGetInt64(val);
             if (node->offset < 0)
                 ereport(ERROR,
-                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+                        (errcode(ERRCODE_INVALID_ROW_COUNT_IN_RESULT_OFFSET_CLAUSE),
                          errmsg("OFFSET must not be negative")));
         }
     }
@@ -274,7 +274,7 @@ recompute_limits(LimitState *node)
             node->count = DatumGetInt64(val);
             if (node->count < 0)
                 ereport(ERROR,
-                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+                        (errcode(ERRCODE_INVALID_ROW_COUNT_IN_LIMIT_CLAUSE),
                          errmsg("LIMIT must not be negative")));
             node->noCount = false;
         }
Index: src/include/utils/errcodes.h
===================================================================
RCS file: /cvsroot/pgsql/src/include/utils/errcodes.h,v
retrieving revision 1.28
diff -u -3 -p -r1.28 errcodes.h
--- src/include/utils/errcodes.h    1 Jan 2009 17:24:02 -0000    1.28
+++ src/include/utils/errcodes.h    27 Feb 2009 11:23:13 -0000
@@ -136,6 +136,8 @@
 #define ERRCODE_INVALID_LIMIT_VALUE            MAKE_SQLSTATE('2','2', '0','2','0')
 #define ERRCODE_INVALID_PARAMETER_VALUE        MAKE_SQLSTATE('2','2', '0','2','3')
 #define ERRCODE_INVALID_REGULAR_EXPRESSION    MAKE_SQLSTATE('2','2', '0','1','B')
+#define ERRCODE_INVALID_ROW_COUNT_IN_LIMIT_CLAUSE    MAKE_SQLSTATE('2', '2', '0', '1', 'W')
+#define ERRCODE_INVALID_ROW_COUNT_IN_RESULT_OFFSET_CLAUSE    MAKE_SQLSTATE('2', '2', '0', '1', 'X')
 #define ERRCODE_INVALID_TIME_ZONE_DISPLACEMENT_VALUE    MAKE_SQLSTATE('2','2', '0','0','9')
 #define ERRCODE_INVALID_USE_OF_ESCAPE_CHARACTER        MAKE_SQLSTATE('2','2', '0','0','C')
 #define ERRCODE_MOST_SPECIFIC_TYPE_MISMATCH MAKE_SQLSTATE('2','2', '0','0','G')