When you use .reopen() from an existing reader, the new reader will share sub-readers with the prior one, and the FieldCache will also share cache entries for those sub readers, with the prior one.
Still, remember that the incrementality you'll see is in proportion to the size of the new segments. EG, if you optimize from the writer before closing, then IR.reopen buys you nothing since no segments can be reused from the prior reader. Also, if a large merge completes, that large segment must be opened for the new reader. If this becomes a problem you should warm the new reader before swapping it into production. NRT (IndexWriter.getReader), at least in the current impl, is just like reopen, except it saves having to close/commit from IndexWriter (which can be costly since it must fsync all newly created files), it's also able in some cases to carry pending deletions in RAM instead of going through the filesystem, and it's able to warm a newly merged segment in the BG before it's committed to the index, without blocking the reopen. Mike On Mon, Jun 7, 2010 at 2:02 PM, Woolf, Ross <ross_wo...@bmc.com> wrote: > I'm looking for some clarification on the use of field cache in a real time > index situation. > > We are using Lucene in a real time fashion, but we update our reader via > IndexReader.reopen() rather than using the IndexWriter.getReader(); After > opening a new reader the old reader is closed. > > In the book Lucene in Action (2nd) it mentions something regarding since > 2.9.2 you can pass in a subreader instead of the reader if you are reopening > a reader so that you only have to load the new segment. But it is not clear > on how all of this works. > > My big question is does doing it this way mean that I can reuse the portion > of the cache that was created with prior readers? Or does the whole cache > have to be rebuilt each time I do a reopen? I guess what I am asking is if > in a real time situation, since I will be reopening readers regularly, is my > cache constantly having to be rebuilt from scratch, or can I use this > subreader approach to sequentially add to the cache? > > Also if the approach lets me sequentially add to the cache, how exactly do I > go about dealing with the subreaders? All I have used before is my primary > reader and as I perform a reopen, how do I know what subreader to pass into > the fieldcache? > > Any info appreciated. > --------------------------------------------------------------------- To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org For additional commands, e-mail: java-user-h...@lucene.apache.org
