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https://issues.apache.org/jira/browse/LUCENE-1593?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12698204#action_12698204
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Michael McCandless commented on LUCENE-1593:
--------------------------------------------

bq. Change TSDC and TFC's code to not use the doc id as a tie breaker.

We have to remember that out-of-order docID collectors (BooleanScorer) cannot 
apply this optimization.  When we get to this, lets make sure we have a test 
case that does out-of-order collection, with a field search, that shows failure 
if we fail to break ties by docID.

Actually, the optimization can be applied sometimes: if we can push bottomVal 
testing down to each TermDocs enum (much like unfactoring random-access filter 
down to the TermDocs), that first pass collection in BooleanScorer is in fact 
in order.  But that's a deeper optimization...

> 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
>
>
> 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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