Re: leaky views, yet again

(2010/07/08 22:08), Robert Haas wrote:
> I think we pretty much have conceptual agreement on the shape of the
> solution to this problem: when a view is created with CREATE SECURITY
> VIEW, restrict functions and operators that might disclose tuple data
> from being pushed down into view (unless, perhaps, the user invoking
> the view has sufficient privileges to execute the underlying query
> anyhow, e.g. superuser or view owner). What we have not resolved is
> exactly how we're going to decide which functions and operators might
> do such a dastardly thing. I think the viable options are as follows:
>
> 1. Adopt Heikki's proposal of treating indexable operators as non-leaky.
>
> http://archives.postgresql.org/pgsql-hackers/2010-06/msg00291.php
>
> Or, perhaps, and even more restrictively, treat only
> hashable/mergeable operators as non-leaky.
>
> 2. Add an explicit flag to pg_proc, which can only be set by
> superusers (and which is cleared if a non-superuser modifies it in any
> way), allowing a function to be tagged as non-leaky. I believe that
> it would be reasonable to set this flag for all of our built-in
> indexable operators (though I'd read the code before doing it), but it
> would remove the need for the assumption that third-party operators
> are equally sane.
>
> CREATE OR REPLACE FUNCTION doesnt_leak() RETURNS integer AS $$SELECT
> 42$$ IMMUTABLE SEAWORTHY; -- doesn't leak
>
> This problem is not going away, so we should try to decide on something.
>
I'd like to vote the second option, because this approach will be also
applied on another aspect of leaky views.

When leaky and non-leaky functions are chained within a WHERE clause,
it will be ordered by the cost of functions. So, we have possibility
that leaky functions are executed earlier than non-leaky functions.

It will not be an easy work to mark built-in functions as either leaky
or non-leaky, but it seems to me the most straight forward solution.

Thanks,
--
KaiGai Kohei <kaigai(at)ak(dot)jp(dot)nec(dot)com>