Re: [Postgres-xc-developers] Understanding how coordinator collects data from datanodes

[Manikandan S. <ma...@vt...>]

Hi Ashutosh,

Thanks for the reply. Do you mean the COPY command like the following
that we use to copy query result to a file,

COPY (select * from xxx) to '/home/xx.txt'

Thanks
Mani

On Fri, 2015-05-15 at 12:43 +0530, Ashutosh Bapat wrote:
> 
> 
> On Fri, May 15, 2015 at 12:13 PM, Manikandan Soundarapandian
> <ma...@vt...> wrote:
>         Hi,
>         
>         Am trying to understand how the coordinator node collects
>         query results
>         from the datanodes. I see the method handle_response()
>         in ../backend/pgxc/pool/execRemote.c is called for every
>         connection
>         handle. In an infinite for loop, it collects messages from the
>         data
>         nodes and combines the results. I am confused between the two
>         case
>         statements 'D' and 'd'. What is the difference between these
>         two cases?
>         What exactly is the difference between the methods
>         'HandleDataRow' and
>         'HandleCopyDataRow' and can you give an example when each of
>         these
>         methods are invoked? Please help. This will help in my
>         research work.
>         
> 
> 
> I guess HandleDataRow handles "data" row of a query result. The other
> function handles the output of COPY command. These two have different
> forms.
> 
>  
>         Thanks
>         Mani
>         
>         
>         ------------------------------------------------------------------------------
>         One dashboard for servers and applications across
>         Physical-Virtual-Cloud
>         Widest out-of-the-box monitoring support with 50+ applications
>         Performance metrics, stats and reports that give you
>         Actionable Insights
>         Deep dive visibility with transaction tracing using APM
>         Insight.
>         http://ad.doubleclick.net/ddm/clk/290420510;117567292;y
>         _______________________________________________
>         Postgres-xc-developers mailing list
>         Pos...@li...
>         https://lists.sourceforge.net/lists/listinfo/postgres-xc-developers
> 
> 
> 
> -- 
> Best Wishes,
> Ashutosh Bapat
> EnterpriseDB Corporation
> The Postgres Database Company
>