Re: ON CONFLICT DO UPDATE for partitioned tables

Hi,

On 2018-03-16 18:23:44 -0300, Alvaro Herrera wrote:
> Another thing I noticed is that the split of the ON CONFLICT slot and
> its corresponding projection is pretty weird. The projection is in
> ResultRelInfo, but the slot itself is in ModifyTableState. You can't
> make the projection work without a corresponding slot initialized with
> the correct descriptor, so splitting it this way doesn't make a lot of
> sense to me.
>
> (Now, TBH the split between resultRelInfo->ri_projectReturning and
> ModifyTableState->ps.ps_ResultTupleSlot, which is the slot that the
> returning project uses, doesn't make a lot of sense to me either; so
> maybe there some reason that I'm just not seeing. But I digress.)

The projections for different child tables / child plans can look
different, therefore it can't be stored in ModifyTableState itself. No?

The slot's descriptor is changed to be "appropriate" when necessary:
if (slot->tts_tupleDescriptor != RelationGetDescr(resultRelationDesc))
ExecSetSlotDescriptor(slot, RelationGetDescr(resultRelationDesc));

> So I want to propose that we move the slot to be together with the
> projection node that it serves, ie. we put the slot in ResultRelInfo:

That'll mean we have a good number of additional slots in some cases. I
don't think the overhead of that is going to break the bank, but it's
worth considering.

Greetings,

Andres Freund