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https://issues.apache.org/jira/browse/LUCENE-1593?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12705087#action_12705087
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Shai Erera commented on LUCENE-1593:
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bq. And default Collector.acceptsDocsOutOfOrder should return false.
Do you propose it for back-compat reasons or simply because it makes sense.
Collector is not released yet so we can define that method abstract.
bq. Thoughts on collapsing down all of these classes to 1 or 2 for Lucy in a
post to the Lucy dev list entitled "SortCollector".
I read it, but I'm not sure I agree with everything that you write there. I
need to re-read it more carefully though before I can comment on it. One thing
that caught my eye is that you write "I found one additional inefficiency in
the Lucene implementation: score() is called twice for "competitive" docs".
Where exactly did you see it? I checked TFC's code again and score() is never
called twice. RelevanceComparator wraps the given Scorer with a
ScoreCachingWrapperScorer, so the score() calls return almost immediately,
without computing any scores.
This was a tradeoff we've made because of the TFC instances that don't compute
documents scores, and so we removed the score parameter from
FieldComparator.copy() and compareBottom(). We could have added it back and
pass in the not-scoring versions Float.NEG_INF, but that will not work well,
since we should really compute the document's score if one of the SortField is
RELEVANCE ... hmm - maybe we can change TFC.create() to check the doc fields
and if one of them is RELEVANCE return a ScoringNoMaxScore collector version,
and then we should be safe with adding score back to those methods signature?
> Optimizations to TopScoreDocCollector and TopFieldCollector
> -----------------------------------------------------------
>
> Key: LUCENE-1593
> URL: https://issues.apache.org/jira/browse/LUCENE-1593
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Search
> Reporter: Shai Erera
> Fix For: 2.9
>
> Attachments: LUCENE-1593.patch, LUCENE-1593.patch, PerfTest.java
>
>
> This is a spin-off of LUCENE-1575 and proposes to optimize TSDC and TFC code
> to remove unnecessary checks. The plan is:
> # Ensure that IndexSearcher returns segements in increasing doc Id order,
> instead of numDocs().
> # Change TSDC and TFC's code to not use the doc id as a tie breaker. New docs
> will always have larger ids and therefore cannot compete.
> # Pre-populate HitQueue with sentinel values in TSDC (score = Float.NEG_INF)
> and remove the check if reusableSD == null.
> # Also move to use "changing top" and then call adjustTop(), in case we
> update the queue.
> # some methods in Sort explicitly add SortField.FIELD_DOC as a "tie breaker"
> for the last SortField. But, doing so should not be necessary (since we
> already break ties by docID), and is in fact less efficient (once the above
> optimization is in).
> # Investigate PQ - can we deprecate insert() and have only
> insertWithOverflow()? Add a addDummyObjects method which will populate the
> queue without "arranging" it, just store the objects in the array (this can
> be used to pre-populate sentinel values)?
> I will post a patch as well as some perf measurements as soon as I have them.
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