David Smiley created LUCENE-4574:
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Summary: 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
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.
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