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From "Shai Erera (JIRA)" <>
Subject [jira] Commented: (LUCENE-1593) Optimizations to TopScoreDocCollector and TopFieldCollector
Date Mon, 04 May 2009 20:14:30 GMT


Shai Erera commented on LUCENE-1593:

bq. Whew - that's a lot of change just to sometimes allow BooleanScorer instead of BooleanScorer2

Some of these changes were discussed elsewhere already, e.g. deprecating Weight and Searchable
and make them abstract classes for easier such changes in the future.

Also, it's not just about creating BS2 or BS sometimes ... it's about the changes in this
issue which moved to assume at first in-order documents collection, and thus did not break
ties on doc Ids at the Collector level. In order to allow this to work with the current BS,
we need to have a way to determine which scorer will be used. Or ... we can stop using BS
at all and saying all scorers must work in-order.

Also, it's not that large of change, just lots of text :) (my fault). In the end we'll achieve
some refactoring, and few more deprecated methods.

bq. Another option to consider is use of a thread local to pass this info. A bit of a hack,
but it would be more localized.

I'm not sure I understand this - where would you set it? On IndexSearcher ctor? search methods
(which means changes to the interfaces)? On Scorer (which is most local I can think of)?

> 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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