Re: Optimization for updating foreign tables in Postgres FDW

On 2016/02/15 15:20, Rushabh Lathia wrote:
> On Fri, Feb 12, 2016 at 5:40 PM, Etsuro Fujita
> <fujita.etsuro@lab.ntt.co.jp <mailto:fujita.etsuro@lab.ntt.co.jp>> wrote:

>     As a result of our discussions, we reached a conclusion that the DML
>     pushdown APIs should be provided together with existing APIs such as
>     ExecForeignInsert, ExecForeignUpdate or ExecForeignDelete, IIUC.
>     So, how about (1) leaving the description for the existing APIs
>     as-is and (2) adding a new description for the DML pushdown APIs in
>     parenthesis, like this?:
>
>           If the <function>IsForeignRelUpdatable</> pointer is set to
>           <literal>NULL</>, foreign tables are assumed to be insertable,
>     updatable,
>           or deletable if the FDW provides <function>ExecForeignInsert</>,
>           <function>ExecForeignUpdate</>, or <function>ExecForeignDelete</>
>           respectively.
>           (If the FDW attempts to optimize a foreign table update, it still
>           needs to provide PlanDMLPushdown, BeginDMLPushdown,
>           IterateDMLPushdown and EndDMLPushdown.)
>
>     Actually, if the FDW provides the DML pushdown APIs, (pushdown-able)
>     foreign table updates can be done without ExecForeignInsert,
>     ExecForeignUpdate or ExecForeignDelete.  So, the above docs are not
>     necessarily correct.  But we don't recommend to do that without the
>     existing APIs, so I'm not sure it's worth complicating the docs.

> Adding a new description for DML pushdown API seems good idea. I would
> suggest to add that as separate paragraph rather then into brackets.

OK, will do.

Best regards,
Etsuro Fujita