Re: [0/4] Proposal of SE-PostgreSQL patches

Tom Lane wrote:
> KaiGai Kohei <kaigai@ak.jp.nec.com> writes:
>   
>> Tom Lane wrote:
>>     
>>> Yeah, I remember those.  What needs to be looked at here is *why* the
>>> output is changing.  For a patch that allegedly does not touch the
>>> planner, it's fairly disturbing that you don't get the same results.
>>>       
>
>   
>> SE-PostgreSQL does not touch the planner, but it modifies given query
>> to filter violated tuples for the current user.
>>     
>
> Hmm.  Is that really a good idea, compared to hard-wiring the checks
> into nodeSeqscan and friends?  I didn't look at the query-rewriting
> portion of the patch in any detail, but I'd tend not to trust such
> a technique very far: getting it right is going to be quite complex
> and probably bug prone.
>
>   

My eyebrows went up when I read this too. Presumably, if it's hardwired 
like you suggest then the planner can't take any account of the filter, 
though. Do we want it to?

OTOH, I'm not happy about silently rewriting queries, either - it would 
make optimising queries a lot harder, I suspect.

cheers

andrew