Re: Gather Merge

On Fri, Feb 17, 2017 at 4:47 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
wrote:

> On Fri, Feb 17, 2017 at 3:59 PM, Thomas Munro
> <thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> > On Thu, Feb 2, 2017 at 2:32 AM, Rushabh Lathia <rushabh(dot)lathia(at)gmail(dot)com>
> wrote:
> >> Please find attached latest patch.
> >
> > The latest patch still applies (with some fuzz), builds and the
> > regression tests pass.
> >
> > I see that Robert made a number of changes and posted a v6 along with
> > some numbers which he described as lacklustre, but then fixed a row
> > estimate problem which was discouraging parallel joins (commit
> > 0c2070ce). Rushabh posted a v7 and test results which look good.
> >
>
> Are you suggesting that commit 0c2070ce has helped to improve
> performance if so, I don't think that has been proved? I guess the
> numbers are different either due to different m/c or some other
> settings like scale factor or work_mem.
>

I don't really think 0c2070ce is the exact reason. I run the tpch runs
with the same same setting as what Robert was running. I haven't
noticed any regression with the runs. For the last runs I also
uploaded the tpch run outputs for the individual queries for the
reference.

> > As
> > far as I can see there are no outstanding issues or unhandled review
> > feedback. I've had a fresh read through of the latest version and
> > have no further comments myself.
> >
> > I've set this to ready-for-committer now. If I've misunderstood and
> > there are still unresolved issues from that earlier email exchange or
> > someone else wants to post a review or objection, then of course
> > please feel free to set it back.
> >
> > BTW There is no regression test supplied. I see that commit 5262f7a4
> > adding parallel index scans put simple explain output in
> > "select_parallel" to demonstrate the new kind of plan being created;
>
> It has added both explain statement test and a test to exercise
> parallel index scan code.
>
>
Thanks for the reference. I added the similar tests for GM in the
uploaded latest patch.

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

--
Rushabh Lathia