Re: Optimization for updating foreign tables in Postgres FDW

On Thu, Jan 28, 2016 at 11:33 AM, Etsuro Fujita <fujita.etsuro@lab.ntt.co.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?

Best regards,
Etsuro Fujita