Re: [HACKERS] Proposal : Parallel Merge Join - Mailing list pgsql-hackers

From Dilip Kumar
Subject Re: [HACKERS] Proposal : Parallel Merge Join
Date
Msg-id CAFiTN-uRuD9acs_yU22e2=OG=dr_isUyzRwu7coAM-cPE=Zfgg@mail.gmail.com
Whole thread Raw
In response to Re: [HACKERS] Proposal : Parallel Merge Join  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
List pgsql-hackers
On Thu, Dec 29, 2016 at 3:15 AM, Tomas Vondra
<tomas.vondra@2ndquadrant.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



pgsql-hackers by date:

Previous
From: Amit Kapila
Date:
Subject: Re: [HACKERS] pg_stat_activity.waiting_start
Next
From: Amit Kapila
Date:
Subject: Re: [HACKERS] Duplicate node tag assignments