Re: Parallel Seq Scan

On Thu, Oct 15, 2015 at 5:39 PM, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>
wrote:
>
>
>
> On Thu, Oct 15, 2015 at 6:32 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
wrote:
> > On Wed, Oct 14, 2015 at 3:29 AM, Robert Haas <robertmhaas(at)gmail(dot)com>
wrote:
> > I think this got messed up while rebasing on top of Gather node
> > changes, but nonetheless, I have changed it such that PartialSeqScan
> > node handling is after SeqScan.
>
> Currently, the explain analyze of parallel seq scan plan is not showing
the allocated number of workers
> including the planned workers.I feel this information is good for users
in understanding the performance
> difference that is coming with parallel seq scan. It may be missed in
recent patch series. It was discussed
> in[1].
>

I am aware of that and purposefully kept it for a consecutive patch.
There are other things as well which I have left out from this patch
and those are:
a. Early stop of executor for Rescan purpose
b. Support of pushdown for plans containing InitPlan and SubPlans

Then there is more related work like
a. Support for prepared statements

Basically I think this could be done as add on patches once we are
done with basic patch.

> Currently there is no qualification evaluation at Result and Gather
nodes, because of this reason, if any
> query that contains any parallel restricted functions is not chosen for
parallel scan. Because of
> this reason, there is no difference between parallel restricted and
parallel unsafe functions currently.
>

This requires new infrastructure to pull restricted functions from
lower nodes to Gather node, so I have left it for another day.

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