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From "Michael McCandless (JIRA)" <>
Subject [jira] Commented: (LUCENE-1593) Optimizations to TopScoreDocCollector and TopFieldCollector
Date Wed, 06 May 2009 10:57:30 GMT


Michael McCandless commented on LUCENE-1593:

Patch looks good!  I can confirm that all tests pass.  (Though the back-compat tag has moved
forward -- I just carried that part of the patch forward).  Thanks Shai.

Some small comments:

  * No need to call out the API change to HitQueue in CHANGES.txt
    (it's package private)

  * Can't the out-of-order TFC classes do the "pre-populate pqueue w/
    sentinel" optimization?

  * There are some leftover javadocs references to
    Query#scoresDosInOrder (in at least TSDC)

  * I don't think we should this yet, but..: it'd be conceivably
    possible at indexing time to record if a given field ever uses the
    sentinel value for that field's type.  If it doesn't, we can also
    safely pre-fill the queue w/ sentinels even for in-order scoring.
    (There are many barriers to doing this optimization today in

> Optimizations to TopScoreDocCollector and TopFieldCollector
> -----------------------------------------------------------
>                 Key: LUCENE-1593
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Search
>            Reporter: Shai Erera
>             Fix For: 2.9
>         Attachments: LUCENE-1593.patch, LUCENE-1593.patch, LUCENE-1593.patch,
> 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
> # 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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