Hey Stuart, Lucene solely relies on the FS cache with some exceptions for the term-dictionary and FieldCache which is pulled entirely into memory. FieldCache is not used to retrieve stored fields though, its rather an univerted view (docID -> value) of an indexed (inverted) field. So basically what you see is likely filesystem memory / cache ie. your documents are "hot". In general you should fire up some warmup queries before you swap your search in to serve user queries to get best performance.
hope that helps simon On Fri, Feb 24, 2012 at 10:18 PM, Rose, Stuart J <stuart.r...@pnnl.gov> wrote: > > Lucene (using 3.5) seems to be caching field values for documents (after they > have been retrieved) and I am hoping someone can provide more information on > how and where exactly the field values are stored. > > The table below lists the times (in milliseconds) associated with retrieving > for a set of documents matching a particular query a single stored value from > each document in the set. Results are shown for three queries (A, B, and C) > submitted multiple times. The first time each query is submitted, the time to > retrieve it's matching document values is considerably longer than any time > after that. > > 1) search A nDocs = 489 time = 1342 > 2) search A nDocs = 489 time = 811 > 3) search B nDocs = 47038 time = 76658 > 4) search B nDocs = 47038 time = 1062 > 5) search C nDocs = 5256 time = 22741 > 6) search C nDocs = 5256 time = 578 > 7) search A nDocs = 489 time = 515 > 8) search A nDocs = 489 time = 514 > 9) search B nDocs = 47038 time = 1000 > 10) search B nDocs = 47038 time = 967 > 11) search C nDocs = 5256 time = 563 > 12) search C nDocs = 5256 time = 562 > > > Whatever information that is being cached is available across separate > processes so presumably it is residing somewhere in the file system (and/or > virtual memory). I have also seen the same behavior when retrieving > TermFreqVector information as well. > > Any additional insight is appreciated! > > Thanks, > Stuart > > > __________________________________________________ > Stuart Rose > Senior Research Engineer > Pacific Northwest National Laboratory > --------------------------------------------------------------------- To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org For additional commands, e-mail: java-user-h...@lucene.apache.org
