Andres Freund wrote: > 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));
Grumble. This stuff looks like full of cheats to me, but I won't touch it anyway. > > 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. Good point. I think what I should be doing is the same as the returning stuff: keep a tupdesc around, and use a single slot, whose descriptor is changed just before the projection. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
