Re: Odd behavior in foreign table modification (Was: Re: Optimization for updating foreign tables in Postgres FDW)

On Thu, Jan 21, 2016 at 4:05 AM, Etsuro Fujita
<fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
>> By the way, I'm not too sure I understand the need for the core
>> changes that are part of this patch, and I think that point merits
>> some discussion. Whenever you change core like this, you're changing
>> the contract between the FDW and core; it's not just postgres_fdw that
>> needs updating, but every FDW. So we'd better be pretty sure we need
>> these changes and they are adequately justified before we think about
>> putting them into the tree. Are these core changes really needed
>> here, or can we fix this whole issue in postgres_fdw and leave the
>> core code alone?
>
> Well, if we think it is the FDW's responsibility to insert a valid value for
> tableoid in the returned slot during ExecForeignInsert, ExecForeignUpdate or
> ExecForeignDelete, we don't need those core changes. However, I think it
> would be better that that's done by ModifyTable in the same way as
> ForeignScan does in ForeignNext, IMO. That eliminates the need for
> postgres_fdw or any other FDW to do that business in the callback routines.

I'm not necessarily opposed to the core changes, but I want to
understand better what complexity they are avoiding. Can you send a
version of this patch that only touches postgres_fdw, so I can
compare?

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company