Re: [HACKERS] [PATCH] Push limit to sort through a subquery

On Fri, Aug 25, 2017 at 7:35 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> I'm inclined to commit both of these after a little more testing and
>> self-review, but let me know if anyone else wants to review first.
>
> Looking through the first one, I wondered whether we needed to
> check for a qual expression on Gather or GatherMerge.  It seems like
> it would be stupid to put a filter on that node rather than its
> children, but I see this in both nodeGather.c and nodeGatherMerge.c:
>
>         /*
>          * initialize child expressions
>          */
>         gatherstate->ps.qual =
>                 ExecInitQual(node->plan.qual, (PlanState *) gatherstate);
>
> It doesn't look like the qual is actually used anywhere in either node
> type.  Am I right in thinking this is dead code?
>

I also think so.  I think this was required in some initial versions
of gather node patch where we were thinking of having a single node
(instead of what we have now that Gather node and beneath there will
be partial scan node) to perform parallel scans.

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