Re: allow partial union-all and improve parallel subquery costing

On 14.10.20 09:38, Luc Vlaming wrote:
> Hi,
>
> It seems I ran the wrong make checks to verify everything is correct (make check instead
> of make installcheck-world) and this uncovered another regress test change. I also noticed
> the statistics are sometimes giving different row count results so I increased the row
> statistics target to make sure the regress output is stable. Updated patch attached which
> now successfully runs installcheck-world for v13 and master.
>
> Kind regards,
> Luc
>
> ________________________________________
> From: Luc Vlaming <luc(at)swarm64(dot)com>
> Sent: Tuesday, October 13, 2020 10:57 AM
> To: pgsql-hackers
> Subject: allow partial union-all and improve parallel subquery costing
>
> Hi,
>
> While developing some improvements for TPC-DS queries I found out that with
> UNION ALL partial paths are not emitted. Whilst fixing that I also came across
> the subquery costing which does not seem to consider parallelism when doing
> the costing.
>
> I added a simplified testcase in pg-regress to show this goes wrong, and
> attached also a before and after explain output of tpc-ds SF100 query 5
> based on version 12.4.
>
> I hope I followed all etiquette and these kind of improvements are welcome.
>
> Kind regards,
> Luc
> Swarm64
>

Hi,

Created a commitfest entry assuming this is the right thing to do so
that someone can potentially pick it up during the commitfest.

Kind regards,
Luc
Swarm64