Re: Proposal : Parallel Merge Join

On Thu, Dec 29, 2016 at 3:15 AM, Tomas Vondra
<tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
> FWIW, I've done quite a bit of testing on this patch, and also on the other
> patches adding parallel index scans and bitmap heap scan. I've been running
> TPC-H and TPC-DS on 16GB data sets with each patch, looking for regressions
> or crashes.

Thanks for looking into this.

>
> I haven't found any of that so far, which is good of course. It however
> seems the plan changes only for very few queries in those benchmarks with
> any of the patches, even after tweaking the costs to make parallel plans
> more likely.

You can also try with reducing random_page_cost (that will help
parallel merge join with index scan), in case your data fits in memory
and you are ensuring warm cache environment.

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com