[PATCH] unalias of ACL_SELECT_FOR_UPDATE

Currently, the ACL_SELECT_FOR_UPDATE privilege is defined as an alias
of ACL_UPDATE as follows:

at src/include/nodes/parsenodes.h:
:
/* Currently, SELECT ... FOR UPDATE/FOR SHARE requires UPDATE privileges */
#define ACL_SELECT_FOR_UPDATE ACL_UPDATE
:

It is unconfortable for us because SE-PostgreSQL have two individual
permissions for updates (db_table:{update}) and explicit table locks
(db_table:{lock}), but it unables to discriminate whether the given
relation is actually used for UPDATE or SELECT FOR UPDATE.
So, I would like to define the bit as (1<<12) which is not in use.

I think we have two options to solve the matter.

The one is to check ACL_SELECT_FOR_UPDATE by UPDATE privilege, as
the attached patch doing. It implicitly expands the users privilege
when he has ACL_UPDATE, so it enables GRANT UPDATE to cover both of
ACL_UPDATE and ACL_SELECT_FOR_UPDATE as the current implementation
doing.

The other is to add a new privilege for explicit table locks, such
as something like LOCK privilege. It is a straightforward approach,
but we need to have a user visible changes.

Which is more preferable design?

Thanks,
--
OSS Platform Development Division, NEC
KaiGai Kohei <kaigai(at)ak(dot)jp(dot)nec(dot)com>