Re: partition routing layering in nodeModifyTable.c

Hi,

On 2019-08-03 05:20:35 +0900, Etsuro Fujita wrote:
> On Sat, Aug 3, 2019 at 3:01 AM Andres Freund <andres@anarazel.de> wrote:
> > On 2019-07-31 17:04:38 +0900, Amit Langote wrote:
> > > I looked into trying to do the things I mentioned above and it seems
> > > to me that revising BeginDirectModify()'s API to receive the
> > > ResultRelInfo directly as Andres suggested might be the best way
> > > forward.  I've implemented that in the attached 0001.
>
> > Fujita-san, do you have any comments on the FDW API change?  Or anybody
> > else?
> >
> > I'm a bit woried about the move of BeginDirectModify() into
> > nodeModifyTable.c - it just seems like an odd control flow to me. Not
> > allowing any intermittent nodes between ForeignScan and ModifyTable also
> > seems like an undesirable restriction for the future. I realize that we
> > already do that for BeginForeignModify() (just btw, that already accepts
> > resultRelInfo as a parameter, so being symmetrical for BeginDirectModify
> > makes sense), but it still seems like the wrong direction to me.
> >
> > The need for that move, I assume, comes from needing knowing the correct
> > ResultRelInfo, correct?  I wonder if we shouldn't instead determine the
> > at plan time (in setrefs.c), somewhat similar to how we determine
> > ModifyTable.resultRelIndex. Doesn't look like that'd be too hard?
>
> I'd vote for that; I created a patch for that [1].
>
> [1] https://www.postgresql.org/message-id/CAPmGK15%3DoFHmWNND5vopfokSGfn6jMXVvnHa7K7P49F7k1hWPQ%40mail.gmail.com

Oh, missed that. But that's not quite what I'm proposing. I don't like
ExecFindResultRelInfo at all. What's the point of it? It's introduction
is still an API break - I don't understand why that break is better than
just passing the ResultRelInfo directly to BeginDirectModify()?  I want
to again remark that BeginForeignModify() does get the ResultRelInfo -
it should have been done the same when adding direct modify.

Even if you need the loop - which I don't think is right - it should
live somewhere that individual FDWs don't have to care about.

- Andres