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https://issues.apache.org/jira/browse/LUCENE-2878?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Simon Willnauer updated LUCENE-2878:
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Attachment: LUCENE-2878.patch
Attaching my current state - still rough & work in progress though....
In this patch I added a PositionsIntervalIterator returned from
Scorer#positions() and implemented some usecases like filtering Near / Within
(unordered) with Term & BooleanScorer2. BooleanScorer2 if in conjunction mode
now has a PositionIntervalIter implementation that returns the minimal interval
of its unordered query terms and can easily be filtered within a range of pos
(range, first) or within a relative positions (near) simply by wrapping it in
PositionFilterQuery. An example for this is in TestBooleanQuery. The
PosIntervalIterator decouples positional operation nicely from Scoring /
matching so a Boolean AND query gets the normal query score but can be
restricted further based on positions. Even adding positional scoring can
simple be plugged on top of it.
Further, with a specialized Collector implementation - positions could be
fetched only if the score is within the top N to prevent positions matching
for all documents.
One big problem is BooleanScorer which does the bucket based scoring - I will
ignore that one for now. I need to run some benchmarks to see if that does any
good though but haven't had time to do so. If somebody has time and take a look
at this patch - feedback would be very much appreciated.
> Allow Scorer to expose positions and payloads aka. nuke spans
> --------------------------------------------------------------
>
> Key: LUCENE-2878
> URL: https://issues.apache.org/jira/browse/LUCENE-2878
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Search
> Affects Versions: Bulk Postings branch
> Reporter: Simon Willnauer
> Assignee: Simon Willnauer
> Attachments: LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch
>
>
> Currently we have two somewhat separate types of queries, the one which can
> make use of positions (mainly spans) and payloads (spans). Yet Span*Query
> doesn't really do scoring comparable to what other queries do and at the end
> of the day they are duplicating lot of code all over lucene. Span*Queries are
> also limited to other Span*Query instances such that you can not use a
> TermQuery or a BooleanQuery with SpanNear or anthing like that.
> Beside of the Span*Query limitation other queries lacking a quiet interesting
> feature since they can not score based on term proximity since scores doesn't
> expose any positional information. All those problems bugged me for a while
> now so I stared working on that using the bulkpostings API. I would have done
> that first cut on trunk but TermScorer is working on BlockReader that do not
> expose positions while the one in this branch does. I started adding a new
> Positions class which users can pull from a scorer, to prevent unnecessary
> positions enums I added ScorerContext#needsPositions and eventually
> Scorere#needsPayloads to create the corresponding enum on demand. Yet,
> currently only TermQuery / TermScorer implements this API and other simply
> return null instead.
> To show that the API really works and our BulkPostings work fine too with
> positions I cut over TermSpanQuery to use a TermScorer under the hood and
> nuked TermSpans entirely. A nice sideeffect of this was that the Position
> BulkReading implementation got some exercise which now :) work all with
> positions while Payloads for bulkreading are kind of experimental in the
> patch and those only work with Standard codec.
> So all spans now work on top of TermScorer ( I truly hate spans since today )
> including the ones that need Payloads (StandardCodec ONLY)!! I didn't bother
> to implement the other codecs yet since I want to get feedback on the API and
> on this first cut before I go one with it. I will upload the corresponding
> patch in a minute.
> I also had to cut over SpanQuery.getSpans(IR) to
> SpanQuery.getSpans(AtomicReaderContext) which I should probably do on trunk
> first but after that pain today I need a break first :).
> The patch passes all core tests
> (org.apache.lucene.search.highlight.HighlighterTest still fails but I didn't
> look into the MemoryIndex BulkPostings API yet)
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