Re: Optimization for updating foreign tables in Postgres FDW

On 2016/01/28 15:20, Rushabh Lathia wrote:
> On Thu, Jan 28, 2016 at 11:33 AM, Etsuro Fujita
> <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp <mailto:fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>> wrote:
>
> On 2016/01/27 21:23, Rushabh Lathia wrote:
>
> If I understood correctly, above documentation means, that if
> FDW have
> DMLPushdown APIs that is enough. But in reality thats not the
> case, we
> need ExecForeignInsert, ExecForeignUpdate, or ExecForeignDelete
> in case
> DML is not pushable.
>
> And here fact is DMLPushdown APIs are optional for FDW, so that
> if FDW
> don't have DMLPushdown APIs they can still very well perform the DML
> operations using ExecForeignInsert, ExecForeignUpdate, or
> ExecForeignDelete.

> I agree with you. I guess I was wrong. sorry.
>
> So documentation should be like:
>
> If the IsForeignRelUpdatable pointer is set to NULL, foreign
> tables are
> assumed to be insertable, updatable, or deletable if the FDW
> provides
> ExecForeignInsert, ExecForeignUpdate, or ExecForeignDelete
> respectively,
>
> If FDW provides DMLPushdown APIs and the DML are pushable to the
> foreign
> server, then FDW still needs ExecForeignInsert,
> ExecForeignUpdate, or
> ExecForeignDelete for the non-pushable DML operation.
>
> What's your opinion ?

> I agree that we should add this to the documentation, too.
>
> BTW, if I understand correctly, I think we should also modify
> relation_is_updatabale() accordingly. Am I right?

> Yep, we need to modify relation_is_updatable().

OK, will do.

Best regards,
Etsuro Fujita