Re: speeding up planning with partitions

On Sun, Mar 31, 2019 at 12:59 AM Robert Haas <robertmhaas@gmail.com> wrote:
>
> On Sat, Mar 30, 2019 at 11:46 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > > The only problem with PartitionPruneInfo structures of which I am
> > > aware is that they rely on PartitionDesc offsets not changing. But I
> > > added code in that commit in ExecCreatePartitionPruneState to handle
> > > that exact problem.  See also paragraph 5 of the commit message, which
> > > begins with "Although in general..."
> >
> > Ah.  Grotty, but I guess it will cover the issue.
>
> I suppose it is.  I am a little suspicious of the decision to make
> PartitionPruneInfo structures depend on PartitionDesc indexes.

Fwiw, I had complained when reviewing the run-time pruning patch that
creating those maps in the planner and putting them in
PartitionPruneInfo might not be a good idea, but David insisted that
it'd be good for performance (in the context of using cached plans) to
compute this information during planning.

Thanks,
Amit