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From "Michael McCandless (JIRA)" <>
Subject [jira] Commented: (LUCENE-1593) Optimizations to TopScoreDocCollector and TopFieldCollector
Date Thu, 30 Apr 2009 10:26:30 GMT


Michael McCandless commented on LUCENE-1593:

Another "things we should improve about the Scorer API":

Enrich Scorer API to optionally provide more details on positions that
caused a match to occur.

This would improve highlighting (LUCENE-1522) since we'd know exactly
why a match occurred (single source) rather than trying to
reverse-engineer the match.

It'd also address a number of requests over time by users on "how can
I get details on why this doc matched?".

I *think* if we did this, the *SpanQuery would be able to share much
more w/ their "normal" counterparts; this was discussed @
Ie we would have a single TermQuery, just as efficient as the one
today, but it would expose a "getMatches" (say) that enumerates all
positions that matched.

Then, if one wanted these details for every hit on in the topN, we
could make an IndexReader impl that wraps TermVectors for the docs in
the topN (since TermVectors are basically a single-doc inverted
index), run the query on it, and request the match details per doc.

> 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,
> 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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