Re: [Postgres-xc-general] Looks like co-ordinator is my perf bottleneck....somebody help...

[Sandeep G. <gup...@gm...>]

Nirmal,

 Coordinator time is a function of sum of the output from each datanode.
PGXC shows performance when the datanodes output small amount of data
compared to original size.

-Sandeep



On Sat, Feb 1, 2014 at 11:46 AM, Nirmal <sha...@gm...> wrote:

> Hi Koichi,
>
> My tables are not replicated. They all are distributed the way you
> explained.
> For example, total record in one table is 600000 and i have 6 nodes so
> each and every node has got 100000 records.
>
> Now the issue is that when I am running my query directly on data node it
> comes up in 5 sec and it is taking the same time on each and every node so
> it should take the same time if i run the query through coordinator but
> somehow instead on 5sec it's taking 22 sec. So somehow the query execution
> on nodes are happening correctly but data movement from nodes to
> coordinator is taking a lot of time.
>
> Please advise.
>
> Sent from my iPhone
>
> > On Feb 1, 2014, at 12:17 AM, Koichi Suzuki <koi...@gm...>
> wrote:
> >
> > It is not a good way to replicate all the tables for write
> > scalability.   The best way is to distribute transaction tables (very
> > frequently written ones) and replicate master tables (less frequently
> > written and frequently joined with transaction tables).
> >
> > Example is our DBT-1 benchmark.  Slide 12 of
> >
> http://postgres-xc.sourceforge.net/misc-docs/20120614_PGXC_Tutorial_global.pdf
> > shows how we designed DBT-1 table distribution for XC.  I hope this
> > helps.
> >
> > Regards;
> > ---
> > Koichi Suzuki
> >
> >
> > 2014-02-01 Nirmal Sharma <sha...@gm...>:
> >> Hi,
> >>
> >> I created a pgxc cluster with one coordinator, one GTM and 6 data nodes
> (all
> >> on same big machine ).
> >> To test the performance, i ran one query through coordinator on my data
> >> which is evenly distributed on all the nodes and it took total 25 sec to
> >> complete.
> >>
> >> And then i ran the same query on datanodes directly and it took 5 sec on
> >> each and every datanodes.
> >>
> >> Since query execution happens parallely on data nodes so ideally even
> if i
> >> run the query through coordinator, it should not take more than 5-8 sec
> max
> >> but i dont understand why is it taking 25 sec.
> >>
> >> Can somebody help me.?
> >> Do i need to make some changes to my cluster configuration?
> >>
> >>
> >> Regards
> >> Nirmal
> >>
> >>
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