Re: [COMMITTERS] pgsql: Add a hook in ExecCheckRTPerms().

On Jul 11, 2010, at 10:44 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
>> On Fri, 2010-07-09 at 17:21 -0400, Tom Lane wrote:
>>> I'd still want to see some evidence showing that it's worth
>>> troubling over though. Premature optimization being the root of all
>>> evil, and all that. (In this case, the hazard we expose ourselves to
>>> seems to be security holes due to missed resets of the flag.)
>
>> If we did this it would be to add one line to the code
>> if (!perms_ok)
>
>> That doesn't seem to fall into the category of evil optimization to me.
>
> The problem I foresee is not in the testing of the flag, it's in the
> setting/resetting of it. It's a reliability penalty not a performance
> penalty --- and any mistakes would count as security issues.
>
> Now it may be that you can offer a convincing argument that no such
> mistake/oversight is likely. But you haven't even tried to make that
> case. Even if you can show that the risk is small, it's not going to
> be zero, so we have to trade it off against a demonstrated performance
> improvement.

There's no point in going back and forth here until we have a patch and the results of some performance testing using said patch. If Simon writes one and submits it with some results, we'll consider it on the merits. I think that's all Simon is asking for, and I don't think anyone is seriously arguing anything to the contrary. Like Tom, I'm skeptical that there is much performance to be found here, but if I'm wrong, I'm happy to have someone demonstrate it.

...Robert