[Postgres-xl-developers] Issues with "VIEW" composite types on datanodes

Nikhil Sontakke nikhils at translattice.com
Mon Oct 20 00:24:32 PDT 2014


> The background that views are defined only at coordinator is views may
> not be pushable to datanodes.


The re-writing happens on the coordinator and then the planner works with
the original tables to come up with a suitable plan. Unless we use "EXECUTE
DIRECT", I do not see a way views will get pushed as is to the datanodes by
the coordinator.

Regards,
Nikhils


> For safety, views are not allowed to
> propagate to datanodes.
>
> Regards;
> ---
> Koichi Suzuki
>
>
> 2014-10-17 19:45 GMT+09:00 Nikhil Sontakke <nikhils at translattice.com>:
> > Hi,
> >
> > So, I was taking a look at:
> >
> > https://sourceforge.net/p/postgres-xl/tickets/2/
> >
> > The basic issue is that views are not created on datanodes and hence the
> > corresponding composite type also does not exist there.
> >
> > So any query which tries to access such a composite type errors out on
> the
> > datanode. For example:
> >
> > create table gh(g int primary key, h int);
> > create view view_gh as select * from gh;
> > select * from view_gh ;
> > g | h
> > ----+----
> > 1 | 2
> >
> > select view_gh from view_gh ;
> > ERROR: cache lookup failed for type 0
> >
> > One way to solve this could be to allow VIEW creation on datanodes as
> well.
> > If we do that the corresponding composite type will be available there as
> > well.
> >
> > The view will get re-written at the coordinator and presence of the view
> on
> > the datanodes will mostly be for the composite type usage. It's possible
> > that someone might do an "EXECUTE DIRECT" to one of the datanodes, but
> then
> > in that case it will also get re-written appropriately, hopefully. Any
> other
> > issues foreseen?
> >
> > Thoughts?
> >
> > Regards,
> > Nikhils
> >
> > --
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> > Postgres-XL Support
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