On Thu, Jan 8, 2015 at 1:12 AM, Alexander Korotkov <aekorot...@gmail.com> wrote:
> On Tue, Dec 16, 2014 at 4:37 PM, Heikki Linnakangas < > hlinnakan...@vmware.com> wrote: > >> Patch attached. It should be applied on top of my pairing heap patch at >> http://www.postgresql.org/message-id/548ffa2c.7060...@vmware.com. Some >> caveats: >> >> * The signature of the distance function is unchanged, it doesn't get a >> recheck argument. It is just assumed that if the consistent function sets >> the recheck flag, then the distance needs to be rechecked as well. We might >> want to add the recheck argument, like you Alexander did in your patch, but >> it's not important right now. >> > > I didn't get how that expected to work if we have only order by qual > without filter qual. In this case consistent function just isn't called at > all. > > * I used the "distance" term in the executor, although the ORDER BY expr >> machinery is more general than that. The value returned by the ORDER BY >> expression doesn't have to be a distance, although that's the only thing >> supported by GiST and the built-in opclasses. >> >> * I short-circuited the planner to assume that the ORDER BY expression >> always returns a float. That's true today for knn-GiST, but is obviously a >> bogus assumption in general. >> >> This needs some work to get into a committable state, but from a >> modularity point of view, this is much better than having the indexam to >> peek into the heap. > > > Nice idea to put reordering into index scan node. Doesn't look like much > of overengineering. I'm going to bring it to more commitable state. > Following changes has been made in attached patch: * Get sort operators from pathkeys. * Recheck argument of distance function has been reverted. ------ With best regards, Alexander Korotkov.
knn-gist-recheck-5.patch
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