[jira] Commented: (LUCENE-2878) Allow Scorer to expose positions and payloads aka. nuke spans

["Robert Muir (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-2878?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12985121#action_12985121 ] 

Robert Muir commented on LUCENE-2878:
-------------------------------------

I took a quick glance at the issue (not a proper review though: its too easy to get lost in the spans!)
Here are my thoughts/questions:
* I like the idea of adding the positions iterator separate, this is one thing i don't like about the Spans API.
* I don't like the MultiSpansWrapper... it only exists to support PayloadSpanUtil and tests? I don't like PayloadSpanUtil either, i think its a huge trap and it should move to src/test or be removed.
* any ideas of the performance comparison of this patch as-is (SpanScorerWrapper over the Scorer/bulk enum) versus the existing Spans which doesn't use the bulk API?

Seems like if we could get the API how we like on this issue, and fix all codecs bulkpositions implementations to work with payloads, that this would be a nice step
we could make... 


> 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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