Re: [v9.4] row level security - Mailing list pgsql-hackers

On 11/04/2013 11:17 PM, Robert Haas wrote:
> I'd still like to here what's wrong with what I said here:
> 
> http://www.postgresql.org/message-id/CA+TgmoYr1PHw3X9vnVuWDcfXkzK2p_jhtWc0fV2Q58NEgcxyTA@mail.gmail.com

For me, just my understanding. I'm still too new to the planner and
rewriter to grasp that properly as written.

I was responding to Tom's objection, and he makes a good point about
CASE and optimisation. We have to be free to re-order and pre-evaluate
where LEAKPROOF flags make it safe and permissible, without ever
otherwise doing so. That makes the SECURITY BARRIER subquery look
better, since the limited pull-up / push-down is already implemented there.

Robert, any suggesitons on how to approach what you suggest? I'm pretty
new to the planner's guts, but I know there've been some complaints
about the way the current RLS code fiddles with Vars when it changes a
direct scan of a rel into a subquery scan.

The code in:

https://github.com/ringerc/postgres/blob/rls-9.4/src/backend/optimizer/prep/prepunion.c#L1647

and

https://github.com/ringerc/postgres/blob/rls-9.4/src/backend/optimizer/prep/prepunion.c#L1591

seems to be the one folks were complaining about earlier.


-- Craig Ringer                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services