Re: Row level security implementation in Foreign Table in Postgres

Tom, all,

* Tom Lane (tgl@sss.pgh.pa.us) wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> > On Wed, Nov 2, 2016 at 10:46 PM, Sounak Chakraborty <sounakr@gmail.com> wrote:
> >> But my doubt is why this feature is not enabled in case of Foreign Table. (ALTER FOREIGN TABLE doesn't have a
optionof enabling Row Level Security). 
> >> Is this is not implemented due to some limitations in the current design?
> >> Because from a quick view it looks like the security subquery can also be easily attached to the main query and
passedfor processing in foreign database. 
>
> > Yeah, I don't see why that couldn't be made to work.
>
> Once the patch at <30304.1478211798@sss.pgh.pa.us> gets in, the major
> issue will be that FDWs will have to be careful not to select quals for
> optimization (ie pushing down to a remote server) unless they satisfy
> restriction_is_securely_promotable().  In most cases that should be
> about a one-line change in the FDW, but I'm not sure that it'd be a good
> idea to just blindly assume that FDWs are doing that.  We could perhaps
> add some sort of "supports RLS" flag to the FDW API, which would not
> get set unless the FDW author takes positive action to do so.

That sounds like an entirely reasonable approach to me.  Other than
that, I agree that FDWs shouldn't be too difficult to add RLS support
for as it seems pretty clear what the semantics there should be.

Thanks!

Stephen