Re: [PATCH] unalias of ACL_SELECT_FOR_UPDATE

KaiGai Kohei <kaigai(at)ak(dot)jp(dot)nec(dot)com> writes:
> Heikki Linnakangas wrote:
>> What's the point of doing SELECT FOR UPDATE if you're not actually going
>> to UPDATE the row? Having separate permissions for SELECT FOR UPDATE and
>> UPDATE seems useless.

> I wonder why SELECT FOR UPDATE need ACL_UPDATE, although the statement
> itself does not modify any of the given relation.

Because it blocks competing transactions in exactly the same way as an
UPDATE does. I agree with Heikki --- there is no apparent value in
having a separate permission bit for this. Given that AclMode is 3/4ths
full already, I'm not for inventing new privilege types without a very
strong use-case.

A separate bit for SELECT FOR SHARE might possibly make sense given the
strength-of-locking argument. But doing both would eat half of the
available bits, and bring nearer the day that we need a different
representation for AclMode.

regards, tom lane