Re: fixing subplan/subquery confusion

On Tue, Jun 28, 2016 at 8:25 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Amit Kapila <amit.kapila16@gmail.com> writes:
>> I had couple of questions [1] related to that patch.  See if you find
>> those as relevant?
>
> I do not think those cases are directly relevant: you're talking about
> appendrels not single, unflattened RTE_SUBQUERY rels.
>

Right, but still I think we shouldn't leave the appendrel case unattended.

> In the subquery case, my view of how it ought to work is that Paths coming
> up from the subquery would be marked as not-parallel-safe if they contain
> references to unsafe functions.  It might be that that doesn't happen for
> free, but my guess is that it would already work that way given a change
> similar to what I proposed.
>

This makes sense to me.

> In the appendrel case, I tend to agree that the easiest solution is to
> scan all the children of the appendrel and just mark the whole thing as
> not consider_parallel if any of them have unsafe functions.
>

Thats what I had in mind as well, but not sure which is the best place
to set it.  Shall we do it in set_append_rel_size() after setting the
size of each relation (after foreach loop) or is it better to do it in
set_append_rel_pathlist().  Is it better to do it as a separate patch
or to enhance your patch for this change?  If you are okay, I can
update the patch or write a new one based on what is preferred?


-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com