On Sun, Nov 18, 2018 at 3:42 PM Darafei "Komяpa" Praliaskouski <m...@komzpa.net> wrote: > > On Sat, Nov 17, 2018 at 8:51 AM Adam Brusselback <adambrusselb...@gmail.com> > wrote: >> >> > I don't know how much what I write on this thread is read by others or >> how useful this is for others who are following this work >> >> I've been following this thread and many others like it, silently soaking it >> up, because I don't feel like i'd have anything useful to add in most cases. >> It is very interesting seeing the development take place though, so just >> know it's appreciated at least from my perspective. > > I'm also following the development and have hopes about it going forward. Not > much low-level details I can comment on though :) > > In PostGIS workloads, UPDATE table SET geom = ST_CostyFunction(geom, > magicnumber); is one of biggest time-eaters that happen upon initial load and > clean up of your data. It is commonly followed by CLUSTER table using > table_geom_idx; to make sure you're back at full speed and no VACUUM is > needed, and your table (usually static after that) is more-or-less spatially > ordered. I see that zheap can remove the need for VACUUM, which is a big win > already. If you can do something that will allow reorder of tuples according > to index happen during an UPDATE that rewrites most of table, that would be a > game changer :) >
If the tuples are already in the order of the index, then we would retain the order, otherwise, we might not want to anything special for ordering w.r.t index. I think this is important as we are not sure of the user's intention and I guess it won't be easy to do such rearrangement during Update statement. > Another story is Visibility Map and Index-Only Scans. Right now there is a > huge gap between the insert of rows and the moment they are available for > index only scan, as VACUUM is required. Do I understand correctly that for > zheap this all can be inverted, and UNDO can become "invisibility map" that > may be quite small and discarded quickly? > Yeah, eventually that is our goal with the help of delete-marking in indexes, however, for the first version, we still need to rely on visibility maps for index-only-scans. Thank you for showing interest in this work. -- With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com
