Dunno, I'm quite happy with numLargeSegments (you critically misspelled it). It neatly avoids uber-merges, keeps the number of segments at bay, and does not require to recalculate thresholds when my expected index size changes.
The problem is - each person needs his own set of knobs (or thinks he needs them) for MergePolicy, and I can't call any of these sets superior to others :/ 2011/5/2 Shai Erera <ser...@gmail.com>: > I did look at it, but I didn't find that it answers this particular need > (ending with a segment no bigger than X). Perhaps by tweaking several > parameters (e.g. maxLarge/SmallNumSegments + maxMergeSizeMB) I can achieve > something, but it's not very clear what is the right combination. > > Which is related to one of the points -- is it not more intuitive for an app > to set this threshold (if it needs any thresholds), than tweaking all of > those parameters? If so, then we only need two thresholds (size + > mergeFactor), and we can reuse BalancedMP's findBalancedMerges logic > (perhaps w/ some adaptations) to derive a merge plan. > > Shai > > On Mon, May 2, 2011 at 4:42 PM, Earwin Burrfoot <ear...@gmail.com> wrote: >> >> Have you checked BalancedSegmentMergePolicy? It has some more knobs :) >> >> On Mon, May 2, 2011 at 17:03, Shai Erera <ser...@gmail.com> wrote: >> > Hi >> > >> > Today, LogMP allows you to set different thresholds for segments sizes, >> > thereby allowing you to control the largest segment that will be >> > considered for merge + the largest segment your index will hold (=~ >> > threshold * mergeFactor). >> > >> > So, if you want to end up w/ say 20GB segments, you can set >> > maxMergeMB(ForOptimize) to 2GB and mergeFactor=10. >> > >> > However, this often does not achieve your desired goal -- if the index >> > contains 5 and 7 GB segments, they will never be merged b/c they are >> > bigger than the threshold. I am willing to spend the CPU and IO >> > resources >> > to end up w/ 20 GB segments, whether I'm merging 10 segments together or >> > only 2. After I reach a 20GB segment, it can rest peacefully, at least >> > until I increase the threshold. >> > >> > So I wonder, first, if this threshold (i.e., largest segment size you >> > would like to end up with) is more natural to set than thee current >> > thresholds, >> > from the application level? I.e., wouldn't it be a simpler threshold to >> > set >> > instead of doing weird calculus that depend on maxMergeMB(ForOptimize) >> > and mergeFactor? >> > >> > Second, should this be an addition to LogMP, or a different >> > type of MP. One that adheres to only those two factors (perhaps the >> > segSize threshold should be allowed to set differently for optimize and >> > regular merges). It can pick segments for merge such that it maximizes >> > the result segment size (i.e., don't necessarily merge in sequential >> > order), but not more than mergeFactor. >> > >> > I guess, if we think that maxResultSegmentSizeMB is more intuitive than >> > the current thresholds, application-wise, then this change should go >> > into LogMP. Otherwise, it feels like a different MP is needed, because >> > LogMP is already complicated and another threshold would confuse things. >> > >> > What do you think of this? Am I trying to optimize too much? :) >> > >> > Shai >> > >> > >> >> >> >> -- >> Kirill Zakharenko/Кирилл Захаренко >> E-Mail/Jabber: ear...@gmail.com >> Phone: +7 (495) 683-567-4 >> ICQ: 104465785 >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org >> For additional commands, e-mail: dev-h...@lucene.apache.org >> > > -- Kirill Zakharenko/Кирилл Захаренко E-Mail/Jabber: ear...@gmail.com Phone: +7 (495) 683-567-4 ICQ: 104465785 --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org For additional commands, e-mail: dev-h...@lucene.apache.org
