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David Smiley commented on LUCENE-4574: -------------------------------------- I don't have any conviction on what the right answer should be; this area of Lucene is not one I've explored before. If scorer.score() is cheap in general (is it?), then I can see your reservations. Perhaps the solution is to only cache specific Scorers that are or could be expensive. So for me this means adding the cache at FunctionQuery$AllScorer. This cache is as lightweight as a cache can possibly be, remember; no hashtable lookup, just a docid comparison with branch. bq. Also: can we speed up this particular query? why is its score so costly? It's a FunctionQuery tied to a ValueSource doing spatial distance. Applying this very simple cache on my custom ValueSource cut my response time in nearly a half! > FunctionQuery ValueSource value computed twice per document > ----------------------------------------------------------- > > Key: LUCENE-4574 > URL: https://issues.apache.org/jira/browse/LUCENE-4574 > Project: Lucene - Core > Issue Type: Bug > Components: core/search > Affects Versions: 4.0, 4.1 > Reporter: David Smiley > Attachments: LUCENE-4574.patch, Test_for_LUCENE-4574.patch > > > I was working on a custom ValueSource and did some basic profiling and > debugging to see if it was being used optimally. To my surprise, the value > was being fetched twice per document in a row. This computation isn't > exactly cheap to calculate so this is a big problem. I was able to > work-around this problem trivially on my end by caching the last value with > corresponding docid in my FunctionValues implementation. > Here is an excerpt of the code path to the first execution: > {noformat} > at > org.apache.lucene.queries.function.docvalues.DoubleDocValues.floatVal(DoubleDocValues.java:48) > at > org.apache.lucene.queries.function.FunctionQuery$AllScorer.score(FunctionQuery.java:153) > at > org.apache.lucene.search.TopFieldCollector$OneComparatorScoringMaxScoreCollector.collect(TopFieldCollector.java:291) > at org.apache.lucene.search.Scorer.score(Scorer.java:62) > at > org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:588) > at > org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:280) > {noformat} > And here is the 2nd call: > {noformat} > at > org.apache.lucene.queries.function.docvalues.DoubleDocValues.floatVal(DoubleDocValues.java:48) > at > org.apache.lucene.queries.function.FunctionQuery$AllScorer.score(FunctionQuery.java:153) > at > org.apache.lucene.search.ScoreCachingWrappingScorer.score(ScoreCachingWrappingScorer.java:56) > at > org.apache.lucene.search.FieldComparator$RelevanceComparator.copy(FieldComparator.java:951) > at > org.apache.lucene.search.TopFieldCollector$OneComparatorScoringMaxScoreCollector.collect(TopFieldCollector.java:312) > at org.apache.lucene.search.Scorer.score(Scorer.java:62) > at > org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:588) > at > org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:280) > {noformat} > The 2nd call appears to use some score caching mechanism, which is all well > and good, but that same mechanism wasn't used in the first call so there's no > cached value to retrieve. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org For additional commands, e-mail: dev-h...@lucene.apache.org