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https://issues.apache.org/jira/browse/LUCENE-1593?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12703396#action_12703396
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Shai Erera commented on LUCENE-1593:
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bq.EG BooleanWeight.scorer(...) should call BS2's initCountingSumScorer (and/or
somehow forward to BS)?
Ok that "somehow forward to BS" is more problematic than I thought so
initially. BS2.score(Collector) determines whether to instantiate a new BS, add
the scorers and call bs.score(Collector), or to execute the score itself. On
the other hand, it uses the same scorers in next() and skipTo(). Therefore
there's kind of a mutual exclusiveness here: either the scorers are used by BS
or by BS2. They cannot be used by both, unless we clone() them. If we want to
clone them, we need to:
* Create a BS in init().
* Clone all the Scorers and pass them to BS.
* Initialize BS2's countingSumScorer.
* In score(Collector) use the class member of BS.
bq. hmm I wonder why this wasn't done so far?
I think I understand now ... the decision on which path to take can only be
determined after score(Collector) is called, or next()/skipTo(). Before that,
i.e., when BW returns BS2 it does not know how it will be used, right? The
decision is made by IndexSearcher.doSearch depending on whether there's a
filter (next()/skipTo() are used) or not (score(Collector)).
So perhaps we should revert back to having start() on DISI? Since IndexSearcher
can call start before iterating over the docs, but not if it uses
scorer.score(Collector), which is delegated to the scorer. In that case, we
should check whether the countingSumScorer was initialized and if not
initialize it outselves.
Am I missing something?
> 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, 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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