Re: [RFC] Interface of Row Level Security

On Thu, May 31, 2012 at 3:52 PM, Kohei KaiGai <kaigai@kaigai.gr.jp> wrote:
> It may be an option to separate the case into two; a situation to execute
> the given query immediately just after optimization and never reused,
> and others.

Yes.  Simon suggested exactly this a while back, and I agree with him
that we ought to have it.

> Even though the second situation, it may give us better query execution
> plan, if we try to reconstruct query plan just before executor with
> assumption that expects immutable / stable function can be replaced
> by constant value prior to execution.
> In other words, this idea tries to query optimization again on EXECUTE
> statement against to its nature, to replace immutable / stable functions
> by constant value, and to generate wiser execute plan.
> At least, it may make sense to have a flag on prepared statement to
> indicate whether it has possible better plan with this re-construction.

This sounds complex and inefficient to me.

> Then, if so, we will be able to push the stuff corresponding to
> RLSBYPASS into the query optimization, and works transparently
> for users.

You're still going to need a way to make sure that the cluster can be
dumped properly.  RLSBYPASS accomplishes that; your scheme doesn't.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company