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https://issues.apache.org/jira/browse/LUCENE-1593?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12704603#action_12704603
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Michael McCandless commented on LUCENE-1593:
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BTW, I wonder if instead of "Query.scoresDocsInOrder" we should allow one to
ask the Query for either/or?
Ie, a BooleanQuery can produce a scorer that scores docs in order; it's just
lower performance.
Sure, our top doc collectors can accept "in order" or "out of order"
collection, but perhaps one has a collector out there that must get the docs in
order, so shouldn't we be able to ask the Query to give us docs "always in
order" or "doesn't have to be in order"?
Also: I wonder if we would ever want to allow for non-top-scorer usage that
does not return docs in order? Ie, next() would be allowed to yield docs out
of order. Obviously this is not allowed today... but we are now mixing "top vs
not-top" with "out-of-order vs in-order", where maybe they should be
independent? But I'm not sure in practice when one would want to use an
out-of-order non-top iterator.
> 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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