Add new OID alias type regrole

The new type has the scope of whole the database cluster so it doesn't
behave the same as the existing OID alias types which have database
scope,
concerning object dependency. To avoid confusion constants of the new
type are prohibited from appearing where dependencies are made involving
it.

Also, add a note to the docs about possible MVCC violation and
optimization issues, which are general over the all reg* types.

Kyotaro Horiguchi

src/backend/utils/adt/regproc.c

@@ -40,6 +40,7 @@
 #include "utils/lsyscache.h"
 #include "utils/syscache.h"
 #include "utils/tqual.h"
+#include "utils/acl.h"
 
 static char *format_operator_internal(Oid operator_oid, bool force_qualify);
 static char *format_procedure_internal(Oid procedure_oid, bool force_qualify);
@@ -1553,6 +1554,109 @@ regdictionarysend(PG_FUNCTION_ARGS)
 	return oidsend(fcinfo);
 }
 
+/*
+ * regrolein	- converts "rolename" to role OID
+ *
+ * We also accept a numeric OID, for symmetry with the output routine.
+ *
+ * '-' signifies unknown (OID 0).  In all other cases, the input must
+ * match an existing pg_authid entry.
+ *
+ * This function is not needed in bootstrap mode, so we don't worry about
+ * making it work then.
+ */
+Datum
+regrolein(PG_FUNCTION_ARGS)
+{
+	char	   *role_name_or_oid = PG_GETARG_CSTRING(0);
+	Oid			result;
+
+	/* '-' ? */
+	if (strcmp(role_name_or_oid, "-") == 0)
+		PG_RETURN_OID(InvalidOid);
+
+	/* Numeric OID? */
+	if (role_name_or_oid[0] >= '0' &&
+		role_name_or_oid[0] <= '9' &&
+		strspn(role_name_or_oid, "0123456789") == strlen(role_name_or_oid))
+	{
+		result = DatumGetObjectId(DirectFunctionCall1(oidin,
+										 CStringGetDatum(role_name_or_oid)));
+		PG_RETURN_OID(result);
+	}
+
+	/* Normal case: see if the name matches any pg_authid entry. */
+	result = get_role_oid(role_name_or_oid, false);
+
+	PG_RETURN_OID(result);
+}
+
+/*
+ * to_regrole		- converts "rolename" to role OID
+ *
+ * If the name is not found, we return NULL.
+ */
+Datum
+to_regrole(PG_FUNCTION_ARGS)
+{
+	char	   *role_name = PG_GETARG_CSTRING(0);
+	Oid			result;
+
+	result = get_role_oid(role_name, true);
+
+	if (OidIsValid(result))
+		PG_RETURN_OID(result);
+	else
+		PG_RETURN_NULL();
+}
+
+/*
+ * regroleout		- converts role OID to "role_name"
+ */
+Datum
+regroleout(PG_FUNCTION_ARGS)
+{
+	Oid			roleoid = PG_GETARG_OID(0);
+	char	   *result;
+
+
+	if (roleoid == InvalidOid)
+	{
+		result = pstrdup("-");
+		PG_RETURN_CSTRING(result);
+	}
+
+	result = GetUserNameFromId(roleoid, true);
+	if (!result)
+	{
+		/* If OID doesn't match any role, return it numerically */
+		result = (char *) palloc(NAMEDATALEN);
+		snprintf(result, NAMEDATALEN, "%u", roleoid);
+	}
+	PG_RETURN_CSTRING(result);
+}
+
+/*
+ *		regrolerecv	- converts external binary format to regrole
+ */
+Datum
+regrolerecv(PG_FUNCTION_ARGS)
+{
+	/* Exactly the same as oidrecv, so share code */
+	return oidrecv(fcinfo);
+}
+
+/*
+ *		regrolesend	- converts regrole to binary format
+ */
+Datum
+regrolesend(PG_FUNCTION_ARGS)
+{
+	/* Exactly the same as oidsend, so share code */
+	return oidsend(fcinfo);
+}
+
+
 
 /*
  * text_regclass: convert text to regclass