> On Wed, Mar 23, 2022 at 05:32:46PM -0400, Tom Lane wrote: > Dmitry Dolgov <9erthali...@gmail.com> writes: > > On Tue, Mar 22, 2022 at 04:55:49PM -0400, Tom Lane wrote: > >> In short: I would throw out just about all the planner infrastructure > >> that's been proposed so far. It looks bulky, expensive, and > >> drastically undercommented, and I don't think it's buying us anything > >> of commensurate value. > > > Broadly speaking planner related changes proposed in the patch so far > > are: UniqueKey, taken from the neighbour thread about select distinct; > > list of uniquekeys to actually pass information about the specified > > loose scan prefix into nbtree; some verification logic to prevent > > applying skipping when it's not supported. I can imagine taking out > > UniqueKeys and passing loose scan prefix in some other form (the other > > parts seems to be essential) -- is that what you mean? > > My point is that for pure loose scans --- that is, just optimizing a scan, > not doing AM-based duplicate-row-elimination --- you do not need to pass > any new data to btree at all. It can infer what to do on the basis of the > set of index quals it's handed. > > The bigger picture here is that I think the reason this patch series has > failed to progress is that it's too scattershot. You need to pick a > minimum committable feature and get that done, and then you can move on > to the next part. I think the minimum committable feature is loose scans, > which will require a fair amount of work in access/nbtree/ but very little > new planner code, and will be highly useful in their own right even if we > never do anything more. > > In general I feel that the UniqueKey code is a solution looking for a > problem, and that treating it as the core of the patchset is a mistake. > We should be driving this work off of what nbtree needs to make progress, > and not building more infrastructure elsewhere than we have to. Maybe > we'll end up with something that looks like UniqueKeys, but I'm far from > convinced of that.
I see. I'll need some thinking time about how it may look like (will probably return with more questions). The CF item could be set to RwF, what would you say, Jesper?
