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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1593) Optimizations to TopScoreDocCollector and TopFieldCollector
Date Mon, 27 Apr 2009 22:02:30 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1593?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12703412#action_12703412
] 

Michael McCandless commented on LUCENE-1593:
--------------------------------------------

bq.  the decision on which path to take can only be determined after score(Collector) is called,
or next()/skipTo().

Oh I see: the Scorer cannot know on creation if it's the "top" scorer (score(Collector) will
be called), or a secondary one (next()/skipTo(...) will be called).

Hmm yeah maybe back to DISI.start().  I think as long the actual code that will next()/skipTo(...)
through the iterator is the only one that calls start(), the BS/BS2 double-start problem won't
happen?

Really, somehow, it should be explicit when a Scorer will be topmost.  IndexSearcher knows
this when it creates it.

> 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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