Re: FDW for PostgreSQL

On 2013-02-21 09:58:57 -0500, Tom Lane wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> > On 2013-02-21 14:23:35 +0000, Albe Laurenz wrote:
> >> Tom Lane wrote:
> >>> Another thing I was wondering about, but did not change, is that if we're
> >>> having the remote transaction inherit the local transaction's isolation
> >>> level, shouldn't it inherit the READ ONLY property as well?
>
> >> That seems to me like it would be the right thing to do.
>
> > I am not 100% convinced of that. There might be valid usecases where a
> > standby executes queries on the primary that executes that do DML. And
> > there would be no way out of it I think?
>
> How exactly would it do that via an FDW? Surely if the user tries to
> execute INSERT/UPDATE/DELETE against a foreign table, the command would
> get rejected in a read-only transaction, long before we even figure out
> that the target is a foreign table?

I was thinking of querying a remote table thats actually a view. Which
might be using a function that does caching into a table or something.
Not a completely unreasonable design.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services