Re: [Postgres-xc-general] modifying values at the datanode

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

Thanks Michael. I understand. The only issue is that we have an update
query as

update T set T.a = -1 from A where A.x = T.x


Both A and T and distributed by x column. The problem is that coordinator
first does the join and then
calls update several times at each datanode. This is turning out to be too
slow. Would have
been better if the entire query was shipped to the datanodes.

Thanks.
Sandeep



On Sat, Oct 5, 2013 at 6:27 AM, Michael Paquier
<mic...@gm...>wrote:

> On Sat, Oct 5, 2013 at 2:58 AM, Sandeep Gupta <gup...@gm...>
> wrote:
> >  I understand that the datanodes are read only and that updates/insert
> can
> > happen at coordinator.
> You got it.
>
> > Also, it does not allow modification of column over which the records
> are distributed.
> Hum no, 1.1 allows ALTER TABLE that you can use to change the
> distribution type of a table.
>
> > However, in case I know what I am doing, it there anyway possible to
> modify
> > the values directly at datanodes.
> > The modifications are not over column over which distribution happens.
> If you mean by connecting directly to the Datanodes, no. You would
> break data consistency if table is replicated by the way by doing
> that. Let the Coordinator planner do the job and choose the remote
> nodes for you.
>
> There have been discussion to merge Coordinators and Datanodes
> together though. This would allow what you say, with a simpler cluster
> design.
> --
> Michael
>