Here's a rather long blog post I wrote up that might help: http://searchhub.org/2013/08/23/understanding-transaction-logs-softcommit-and-commit-in-sorlcloud/
Best, Erick On Mon, Sep 16, 2013 at 1:43 PM, Shawn Heisey <s...@elyograg.org> wrote: > On 9/16/2013 7:01 AM, Matteo Grolla wrote: > > Can anyone explain me the following things about soft-commit? > > -For searches o access new documents I think a new searcher is opened > after a soft commit. > > How does the near realtime requirement for soft commit match with > the potentially long time taken to warm up caches for the new searcher? > > -Is it a good idea to set > > openSearcher=false in auto commit > > and rely on soft auto commit to see new data in searches? > > That is a very common way for installs requiring NRT updates to get > configured. > > NRTCachingDirectoryFactory, which is the directory class used in the > example since 4.0, is a wrapper around MMapDirectoryFactory, which is > the old default in 3.x. > > For soft commits, the NRT directory keeps small commits in RAM rather > than writing it to the disk, which makes the process of opening a new > searcher happen a lot faster. > > > http://lucene.apache.org/core/4_4_0/core/org/apache/lucene/store/NRTCachingDirectory.html > > If your index rate is very fast or you index large amounts of data, the > NRT directory doesn't gain you much over MMap, but because we made it > the default in the example, it probably doesn't have any performance > detriment. > > Thanks, > Shawn > >
