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From "Shai Erera (JIRA)" <>
Subject [jira] Commented: (LUCENE-1593) Optimizations to TopScoreDocCollector and TopFieldCollector
Date Tue, 05 May 2009 02:58:30 GMT


Shai Erera commented on LUCENE-1593:

bq. shouldn't we do the interface -> abstract class migration (of Weight & Searchable)
under a separate issue?

I think I asked it already but haven't received a concrete answer.

This issue moved TSDC and TFC to always assume "in-order" collection of documents. If BS is
used, they will break for the documents that compare equally to the top of the queue. Therefore
we wanted to be able to create the right variant of TFC/TSDC depending on the Scorer we're
going to get.

I offered somewhere above (or at least intended to) that we keep the changes I've done to
TSDC and TFC (allowing to create in/out-of order variant) and in IndexSearcher always ask
for out-of-order, then in a separate issue make all these changes and really take advantage
of the in-order variants unless BS is used (or any other future Scorer for that matter).

I don't mind doing that. I also volunteer to open the next issue and take care of it. Is that
what you had in mind?

> 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,
> 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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