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Date: Fri, 21 Jan 2011 11:57:45 -0500 (EST)
From: "Simon Willnauer (JIRA)" <jira@apache.org>
To: dev@lucene.apache.org
Subject: [jira] Updated: (LUCENE-2878) Allow Scorer to expose positions and
 payloads aka. nuke spans
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     [ https://issues.apache.org/jira/browse/LUCENE-2878?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Simon Willnauer updated LUCENE-2878:
------------------------------------

    Attachment: LUCENE-2878.patch

here is the patch

> 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
>
>
> 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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