On 28 September 2018 at 14:25, Amit Langote <langote_amit...@lab.ntt.co.jp> wrote: > Looking at the patch itself, does it seem like both the newly added > comments repeat the same point (that we'll need per-partition hi_options > to enable these optimizations) and are pretty close to each other?
Thanks for looking at this. I don't agree that we can skip explaining why one of the optimisations can't be applied just because we've explained why a similar optimisation cannot be applied somewhere close by. I think that the WAL/FSM optimisation can fairly easily be improved on and probably fixed in PG12 as we can just lazily determine per-partition if it can be applied to that partition or not. For the FREEZE optimisation, since we ERROR out in cases where it's requested but is not possible, it does not seem likely we'll ever fix that since to do that we'd need to determine that all partitions have just been truncated or were only just created in this transaction. Since we've both recently done a bit of work in the area of speeding up COPY, then I doubt either of us would like to go and slow it down again by adding a pre-check that goes and opens all the partitions before the copy begins. That's going to have a huge negative performance impact on small copies to 1 partition when there are many partitions attached. So in this regard, you'll notice that the comments are not that similar. One explains that we could improve on it, and the other attempts to mention that it would be surprising if we performed a FREEZE for some partitions but not others. -- David Rowley http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services