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From "Michael McCandless (JIRA)" <>
Subject [jira] Commented: (LUCENE-1849) Add OutOfOrderCollector and InOrderCollector subclasses of Collector
Date Tue, 25 Aug 2009 21:01:59 GMT


Michael McCandless commented on LUCENE-1849:

bq. Any stats on the performance gains here available?

I think somewhere in LUCENE-1483 is the answer to this question, but I can't find it now.
 (We need a whole new search index just for that issue alone!).  But the optimization currently
only applies if the query contains just SHOULD terms plus up to 32 MUST_NOT terms.  More testing
here would be great... the specialized search in LUCENE-1594 also uses out-of-order collection
for certain AND queries but I haven't confirmed if/when that's a win.

Also, are the implications of out of order docids coming back from nextDoc() well documented
(javadoc?, wiki?)?
I guess out of order docids really screw up advance(int), so you should never call advance(int)
if you allowed out of order collection for a Scorer?

Out-of-order scoring is only used for top-scorers today in Lucene, so nextDoc/advance are
not used.  (Though: BooleanScorer, which provides docs out-of-order, is I think able to nextDoc()
through the out-of-order docs, but I don't think we take advantage of that anywhere, though
we could do so to improve performance of BooleanQuery as a sub-clause of BooleanQuery).

> Add OutOfOrderCollector and InOrderCollector subclasses of Collector
> --------------------------------------------------------------------
>                 Key: LUCENE-1849
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Wish
>          Components: Search
>    Affects Versions: 2.9
>            Reporter: Tim Smith
>            Priority: Minor
>             Fix For: 2.9
> I find myself always having to implement these methods, and i always return a constant
(depending on if the collector can handle out of order hits)
> would be nice for these two convenience abstract classes to exist that implemented acceptsDocsOutOfOrder()
as final and returned the appropriate value

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