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https://issues.apache.org/jira/browse/LUCENE-1593?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12704785#action_12704785
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Shai Erera commented on LUCENE-1593:
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bq. add an API to Collector for it to declare if it can handle out-of-order
collection, and then ask for the right Scorer.
Maybe instead add docsOrderSupportedMode() which returns IN_ORDER,
OUT_OF_ORDER, DONT_CARE? I.e., instead of a boolean allow a Collector to say "I
don't really care" (like Mike has pointed out, I think, somewhere above) and
let the Scorer creation code decide which one to create in case it knows any
better. I.e., if we know that BS performs better than BS2, and we get a
Collector saying DONT_CARE, we can always return BS.
Unless we assume that OUT_OF_ORDER covers DONT_CARE either, in which case we
can leave it as returning boolean and document that if a Collector can support
OUT_OF_ORDER, it should always say so, giving the Scorer creator code a chance
to decide what is the best Scorer to return.
In IndexSearcher we can then:
# Where Collector is given as argument, ask it if it about orderness and create
the appropriate Scorer.
# Where we create our own Collector (i.e. TFC and TSDC) decide on our own what
is better. Maybe always ask out-of-order? That way a Query which doesn't only
supports in-order without any optimization for out-of-order can return that
in-order collector. I didn't think of it initially, but Mike is right - every
in-order scorer is also an out-of-order scorer, so this should be fine.
I like the approach of deprecating Weight and creating an abstract class,
though that requires deprecating Searchable and creating an AbstractSearchable
as well. Weight can be wrapped with an AbstractWeightWrapper and passed to the
AbstractWeight methods (much like we do with AbstractHitCollector from
LUCENE-1575), defaulting its scorer(inOrder) method to call scorer()?
This I guess should be done in the scope of that issue, or I revert the changes
done to Query (adding scoresDocsInOrder()), but keep those done to TFC and
TSDC, and make that optimization in a different issue, which will handle
Weight/Searchable and the rest of the changes proposed here?
> 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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