Re: WIP: Upper planner pathification

On Sat, Mar 5, 2016 at 4:51 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Fri, Mar 4, 2016 at 11:31 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >
> > OK, here is a version that I think addresses all of the recent comments:
> >
> > * Fixed handling of parallel-query fields in new path node types.
> > (BTW, I found what seemed to be a couple of pre-existing bugs of
> > the same kind, eg create_mergejoin_path was different from the
> > other two kinds of join as to setting parallel_degree.)
> >
>
> I think the reason for keeping parallel_degree as zero for mergejoin path
is that currently it can't participate in parallelism.
>
>
> *************** create_unique_path(PlannerInfo *root, Re
> *** 1440,1446 ****
> pathnode->path.param_info = subpath-
> >param_info;
> pathnode->path.parallel_aware = false;
> pathnode->path.parallel_safe = subpath->parallel_safe;
> !
> pathnode->path.parallel_degree = 0;
>
> /*
> * Assume the output is unsorted, since we don't necessarily
> have pathkeys
> --- 1445,1451 ----
> pathnode->path.param_info = subpath->param_info;
> pathnode-
> >path.parallel_aware = false;
> pathnode->path.parallel_safe = subpath->parallel_safe;
> ! pathnode-
> >path.parallel_degree = subpath->parallel_degree;
>
> Similar to reason for merge join path, I think this should also be set to
0.
>
> Similarly for LimitPath, parallel_degree should be set to 0.
>

Oops, It seems Robert has made comment upthread that we should set
parallel_degree from subpath except for write paths, so I think the above
comment can be ignored.

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