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https://issues.apache.org/jira/browse/LUCENE-2878?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13062592#comment-13062592
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Mike Sokolov edited comment on LUCENE-2878 at 7/9/11 5:42 PM:
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To make further progress, I think we need to resolve the position API. The
testMultipleDocumentsOr test case illustrates the problem with the approach I
was trying: walking the PositionIterator tree when collecting documents.
Something like the PositionCollector API could work, but I think we still need
to solve the problem Mike M alluded to back at the beginning:
bq. ... a NEAR query could filter these subs in parallel (like a merge sort)
looking for a match, and (I think) then presenting its own union iterator to
whoever consumes it? Ie it'd only let through those positions of each sub that
satisfied the NEAR constraint.
We want to highlight positions that explain why the document matches the query.
Not all terms that match the term queries will count - some of them should be
"filtered out" by near-conditions; ie in a PhraseQuery, matching terms not in
the phrase should not be highlighted. I think if I just register a callback
with the sub-scorers (scoring terms), I would see *all* the terms, right?
Also, I wonder if callers could use the existing Scorer.ScorerVisitor to walk
the Scorer tree and register interest in positions with a scorer?
was (Author: sokolov):
To make further progress, I think we need to resolve the position API. The
testMultipleDocumentsOr test case illustrates the problem with the approach I
was trying: walking the PositionIterator tree when collecting documents.
Something like the PositionCollector API could work, but I think we still need
to solve the problem Mike M alluded to back at the beginning:
bq. ... a NEAR query could filter these subs in parallel (like a merge sort)
looking for a
match, and (I think) then presenting its own union iterator to whoever
consumes it? Ie it'd only let through those positions of each sub
that satisfied the NEAR constraint.
We want to highlight positions that explain why the document matches the query.
Not all terms that match the term queries will count - some of them should be
"filtered out" by near-conditions; ie in a PhraseQuery, matching terms not in
the phrase should not be highlighted. I think if I just register a callback
with the sub-scorers (scoring terms), I would see *all* the terms, right?
Also, I wonder if callers could use the existing Scorer.ScorerVisitor to walk
the Scorer tree and register interest in positions with a scorer?
> 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: core/search
> Affects Versions: Bulk Postings branch
> Reporter: Simon Willnauer
> Assignee: Simon Willnauer
> Labels: gsoc2011, lucene-gsoc-11, mentor
> Attachments: LUCENE-2878-OR.patch, LUCENE-2878.patch,
> LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch, LUCENE-2878.patch,
> LUCENE-2878_trunk.patch, LUCENE-2878_trunk.patch, PosHighlighter.patch,
> PosHighlighter.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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