On Tue, Jun 26, 2018 at 11:40 PM, Andrey V. Lepikhov <a.lepik...@postgrespro.ru> wrote: > I still believe that the patch for physical TID ordering in btree: > 1) has its own value, not only for target deletion, > 2) will require only a few local changes in my code, > and this patches can be developed independently.
I want to be clear on something now: I just don't think that this patch has any chance of getting committed without something like my own patch to go with it. The worst case for your patch without that component is completely terrible. It's not really important for you to actually formally make it part of your patch, so I'm not going to insist on that or anything, but the reality is that my patch does not have independent value -- and neither does yours. I'm sorry if that sounds harsh, but this is a difficult, complicated project. It's better to be clear about this stuff earlier on. > I prepare third version of the patches. Summary: > 1. Mask DEAD tuples at a page during consistency checking (See comments for > the mask_dead_tuples() function). > 2. Still not using physical TID ordering. > 3. Index cleanup() after each quick_vacuum_index() call was excluded. How does this patch affect opportunistic pruning in particular? Not being able to immediately reclaim tuple space in the event of a dead hot chain that is marked LP_DEAD could hurt quite a lot, including with very common workloads, such as pgbench (pgbench accounts tuples are quite a lot wider than a raw item pointer, and opportunistic pruning is much more important than vacuuming). Is that going to be acceptable, do you think? Have you measured the effects? Can we do something about it, like make pruning behave differently when it's opportunistic? Are you aware of the difference between _bt_delitems_delete() and _bt_delitems_vacuum(), and the considerations for hot standby? I think that that's another TODO list item for this patch. -- Peter Geoghegan