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https://issues.apache.org/jira/browse/LUCENE-1593?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12704693#action_12704693
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Michael McCandless commented on LUCENE-1593:
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One further optimization can be enabled if we can properly "mate"
out-of-orderness between Scorer & Collector: BooleanScorer could be
automatically used when appropriate.
Today, one must call "BooleanQuery.setAllowDocsOutOfOrder" which is
rather silly (it's very much an "under the hood" detail of how the
Scorer interacts w/ the Collector). The vast majority of time it's
Lucene that creates the collector, and so now that we can create
Collectors that either do or do not care if docs arrive out of order,
we should allow BooleanScorer when we can.
Though that means we have two ways to score a BooleanQuery:
* Use BooleanScorer2 w/ a Collector that doesn't fallback to docID
to break ties
* Use BooleanScorer w/ a Collector that does fallback
We'd need to test which is most performant (I'm guessing the 2nd
one).
So maybe we should in fact add a "acceptsDocsOutOfOrder" to
Collector.
> 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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