[HACKERS] Simplify calls of pg_class_aclcheck when multiple modes are used

[Michael Paquier]

Hi all,

In a couple of code paths we do the following to check permissions on an
object:
if (pg_class_aclcheck(relid, userid, ACL_USAGE) != ACLCHECK_OK &&
    pg_class_aclcheck(relid, userid, ACL_UPDATE) != ACLCHECK_OK)
    ereport(ERROR, blah);

Wouldn't it be better to simplify that with a single call of
pg_class_aclcheck, gathering together the modes that need to be checked? In
the case above, the call to pg_class_aclcheck would become like that:
if (pg_class_aclcheck(relid, userid,
         ACL_USAGE | ACL_UPDATE) != ACLCHECK_OK)
    ereport(ERROR, blah);

That's not a critical thing, but it would save some cycles. Patch is
attached.
Regards,
-- 
Michael

From e6b23e537d223e4bdb3abada2d761e630c8b27c0 Mon Sep 17 00:00:00 2001
From: Michael Paquier <mich...@otacoo.com>
Date: Wed, 27 Aug 2014 20:45:31 +0900
Subject: [PATCH] Minimize calls of pg_class_aclcheck to minimum necessary

In a couple of code paths, pg_class_aclcheck is called in succession with
multiple different modes set. This patch combines those modes to have a
single call of this function and reduce a bit process overhead for
permission checking.
---
 src/backend/commands/sequence.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index 3b89dd0..6d5f65b 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -546,8 +546,8 @@ nextval_internal(Oid relid)
 	/* open and AccessShareLock sequence */
 	init_sequence(relid, &elm, &seqrel);
 
-	if (pg_class_aclcheck(elm->relid, GetUserId(), ACL_USAGE) != ACLCHECK_OK &&
-		pg_class_aclcheck(elm->relid, GetUserId(), ACL_UPDATE) != ACLCHECK_OK)
+	if (pg_class_aclcheck(elm->relid, GetUserId(),
+						  ACL_USAGE | ACL_UPDATE) != ACLCHECK_OK)
 		ereport(ERROR,
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 errmsg("permission denied for sequence %s",
@@ -759,8 +759,8 @@ currval_oid(PG_FUNCTION_ARGS)
 	/* open and AccessShareLock sequence */
 	init_sequence(relid, &elm, &seqrel);
 
-	if (pg_class_aclcheck(elm->relid, GetUserId(), ACL_SELECT) != ACLCHECK_OK &&
-		pg_class_aclcheck(elm->relid, GetUserId(), ACL_USAGE) != ACLCHECK_OK)
+	if (pg_class_aclcheck(elm->relid, GetUserId(),
+						  ACL_SELECT | ACL_USAGE) != ACLCHECK_OK)
 		ereport(ERROR,
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 errmsg("permission denied for sequence %s",
@@ -801,8 +801,8 @@ lastval(PG_FUNCTION_ARGS)
 	/* nextval() must have already been called for this sequence */
 	Assert(last_used_seq->last_valid);
 
-	if (pg_class_aclcheck(last_used_seq->relid, GetUserId(), ACL_SELECT) != ACLCHECK_OK &&
-		pg_class_aclcheck(last_used_seq->relid, GetUserId(), ACL_USAGE) != ACLCHECK_OK)
+	if (pg_class_aclcheck(last_used_seq->relid, GetUserId(),
+						  ACL_SELECT | ACL_USAGE) != ACLCHECK_OK)
 		ereport(ERROR,
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 errmsg("permission denied for sequence %s",
-- 
2.1.0


-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers